Bacteriology Medialab

Which Gram positive bacilli will show a positive result for urease?

Actinomyces naeslundii

The bacterial species represented by the positive test illustrated in the photograph of a 5% sheep blood agar plate cross streaked with a hemolytic strain of Staphylococcus aureus has been associated with each of the following conditions except:

Acute post-streptococcal glomerulonephritis

The subsurface umbrella-shaped zone of motility seen in this SIM tube (arrow) is characteristic of Listeria monocytogenes. The optimum temperature of incubation to best illustrate this property is:

25C

Match the Gram-stained image to the organism it MOST closely represents.

Bacillus anthrax

Which of the following statements concerning vancomycin resistance in Enterococci is TRUE?

Both ampicillin and vancomycin resistance are found more frequently in E. faecium than in E. faecalis.

Acceptable sources for urine culture from a patient with suspected urinary tract infection include all EXCEPT:

Drainage bag from nephrostomy catheter

Which of the following serological tests would be used for the diagnosis of Q-fever?

EIA or indirect immunoflourescence

In order to identify an isolate as Yersinia enterocolitica, it must be lysine-negative and demonstrate which of the following?

K/A on Kligler's iron agar

Illustrated in this photograph, reading from left to right, are biochemical reactions for indole, Voges Proskauer, Simmons citrate, and Christensen's urea. The bacterial species providing the best fit for the reactions illustrated is:

Klebsiella oxytoca

All of the following agents can be handled using biosafety level 2 practices, EXCEPT:

Marburg virus

Shigella serotyping is performed by using a polyvalent somatic (O) antisera. A Shigella species grew from culture and serotyped as Group B. Which of the following Shigella species serotypes as Group B?

Shigella flexneri

The appearance of the bacterial colonies growing on the surface of the Hektoen Enteric (HE) agar plate shown in the photograph to the right are consistent with all of the following bacterial species EXCEPT: Illustrated in this photograph, reading from left to right, are tubes of Kligler Iron agar (KIA), Sulfide Indole Motility agar, indole broth, Voges Proskauer broth and Simmons citrate. The bacterial species most likely producing the reactions illustrated here is: Shigella serotyping is performed by using a polyvalent somatic (O) antisera. A Shigella species grew from culture and serotyped as Group D. Which of the following Shigella species serotypes as Group D?

Shigella sonnei

A urine culture contains the following organisms: Proteus mirabilis: 2,000 CFU/mL Klebsiella pneumoniae: 10,000 CFU/mL In which of the following urine sources would both organisms be worked up with a full sensitivity?

Suprapubic aspiration

A combination of nontreponemal testing (VDRL or RPR) and treponemal testing (TP-PA or EIA) is used to confirm:

Syphilis

Sulfonamides, such as sulfamethoxazole (SMZ), and trimethoprim (TMP), work by targeting:

Tetrahydrofolate synthesis; preventing bacterial DNA synthesis

When serotyping Salmonella, Shigella, and Escherichia coli 0157:H7, typing should be performed from a non-sugar-containing medium, such as 5% sheep blood agar. The reason for this is which of the following?

To prevent false-positive results

Fluoroquinolones, such as ciprofloxacin, work by targeting:

Topoisomerases, inhibiting bacterial DNA replication

Orthonitrophenyl-b-D-galactopyranosidase (ONPG) is produced by several bacterial species. It acts by cleaving the beta-galactosidase bond of certain disaccharides, such as lactose. An ONPG-positive bacterial species, however, may appear as a "late lactose user" because of the absence of what?

ß-galactoside permease

What is the one principle that is conserved between all continuous monitoring blood culture systems?

CO2 detection

Beta hemolytic colonies grew from the blood culture bottle after 18 hours of incubation (see image). If the gram stain shows gram-positive cocci, which of the following tests would be helpful with making a preliminary identification? Which of the following test is the most useful in differentiating Listeria monocytogenes from Erysipelothrix rhusiopathiae?

Catalase

This organism is very similar to Serratia marcescens, except it is DNAse negative.

Cedecea davisae

A tech receives a call from the floor regarding antimicrobial therapy. The patient culture yielded an aerobic Gram-negative bacillus and the physician would like to use an antibiotic that inhibits cell wall synthesis. Which of the following antibiotics would be the best choice?

Cefazolin

Which of the following media contains the X and V factors necessary for the growth of Haemophilus influenzae?

Chocolate agar

A bone biopsy from a jaw sent to a microbiology laboratory for culture grew out an Actinomyces species. What would be the most probable contributing factor to this infection? The condition most likely to predispose a person to septicemia by viridans streptococci is:

Poor oral hygiene

Illustrated in the image to the right is a tube of tryptophane agar with a positive indole reaction, as seen by the red ring at the top of the medium. It is necessary to use xylene extraction and Ehrlich's reagent rather than the conventional Kovac's reagent when detecting indole production by which of the following organisms?

Porphyromonas asaccharolytica

The colonies illustrated in the composite blood agar/MacConkey agar to the left were recovered from an inflammatory infection of the oral cavity of a 16-year-old student. The colonies on both agar plates incubated anaerobically are small, entire, and smooth with a light gray-yellow pigmentation. Small gram-negative rods arranged singly and in loose clusters had been observed microscopically in a gram-stained preparation. Spot indole and lipase reactions are positive. Note in the image to the right the alk/alk non-fermentative carbohydrate reaction on Kligler Iron agar, with lack of fermentation of the sugars presented in the tubes to the right (asaccharolytic). Select from the multiple choices the name of this anaerobic, asaccharolytic, gram-negative isolate.

Porphyromonas asaccharolytica

The blue color seen in Simmon's citrate agar slant to the right tube shown in this photograph, indicating a positive reaction, results from:

Production of ammonia from ammonium phosphate

What virulence factor is not inherent to bacterium?

Production of opsonins

What tribe is Morganella morganii in?

Proteeae

A purulent fluid was collected between the lung and the chest wall. What is the name of this fluid?

Thoracentesis fluid

Refer to the images on the right. Image A is delta-aminolevulinic acid viewed with ultraviolet light Image B is buffered charcoal yeast extract agar viewed with ultraviolet light Image C is MacConkey agar Image D is DNAse agar. Review each of the following names of the bacterial species with the appearance and reactions of the colonies seen on the media listed. Each is a correct match of the species with its appearance on the media EXCEPT:

Image C = Klebsiella pneumoniae

Blood culture bottles utilized in continuous monitoring systems, such as the BacTec, use resins or charcoal to do which of the following?

Inactivate and absorb out antimicrobial agents

The purpose of the additive SPS (sodium polyanethol sulfonate) that is in continuous monitoring system blood culture bottles, is all of the following EXCEPT?

Inactivates and absorbs out antimicrobial agents

A male urethral specimen was sent to the laboratory for a gonococcal culture and Gram stain. The specimen was received on a calcium alginate swab and cultured to chocolate and Thayer-Martin agars. A Gram stain was performed and presented intracellular and extracellular Gram-negative diplococci. After 24, 48, and 72 hours of 37°C incubation in CO2, no growth was seen on either chocolate or Thayer-Martin agars. Which of the following is the most probable cause for the lack of Neisseria gonorrhoeae growth?

Inappropriate swab was used for collection

Each of the following laboratory characteristics can be used to separate Bacteroides fragilis from the closely related Prevotella/Porphyromonas group of anaerobes EXCEPT: Elizabethkingia is the new genus name for the bacterium formerly called Chryseobacterium meningosepticum, an important agent of neonatal meningitis (now E. meningoseptica). What biochemical characteristic is unique for the family Flavobacteriaceae among the nonfermenters?

Indole production

The bacterial species shown on the blood agar plate illustrated in the photograph was recovered from a blood culture of a patient with fever. The most likely source of infection is which of the following? A budding yeast with pseudohyphae and clusters of gram-positive staphylococci were observed in a Gram stain smear prepared from a positive blood culture. What is the MOST likely source of the infection?

Indwelling catheter

Corynebacterium jeikeium is often associated with which of the following conditions?

Infected indwelling devices in AIDS patients

Which of the following anthrax infections is also known as "woolsorter's disease"?

Inhalation anthrax

Penicillin G, ampicillin, carbenicillin, and methicillin are antimicrobial agents whose MAIN biological function is to:

Inhibit cell wall synthesis

Which one of the following statements about Campylobacter jejuni is false?

It does not require special incubation conditions to grow in culture.

Which one of the following statements about E.coli O157:H7 is false?

It ferments sorbitol rapidly

All of the following statements concerning Clostridioides difficile are true, EXCEPT?

It is an aerobic organism.

All of the following statements about Coxiella burnetii are true, EXCEPT:

It is best diagnosed by culturing of the organism

This organism, identified as a Klebsiella oxytoca, was recovered from the blood of an elderly patient with an infected anal fissure . The Vitek identified this organism as an ESBL. After reviewing the Kirby-Bauer plate and susceptibility interpretations, what is the resistance mechanism demonstrated by this organism?

K-1 beta-lactamase

The small beta-hemolytic bacterial colonies growing on blood agar as shown in the upper photograph were recovered from an induced sputum specimen from a young child with pneumonia. The colonies were slow-growing, small, entire, and show soft beta hemolysis. Plump, Gram-negative coccobacilli, lying singly, in pairs and short chains, are seen on gram stain as illustrated in the lower photomicrograph. Most strains are chemically non-reactive except for a positive oxidase reaction and acid produced from dextrose and maltose. What is the name of the isolate?

Kingella kingae

The cryptococcal antigen test used to diagnosis Cryptococcus neoformans meningitis is based on what type of rapid methodology?

Latex agglutination

A beta-hemolytic gram-positive cocci, isolated from the CSF of an infant, grew on sheep blood agar under aerobic conditions and was resistant to a bacitracin disc. Which of the following tests should be performed for the presumptive identification of the organism?

Latex agglutination test

The anaerobe producing the double zone of hemolysis, seen in this photograph, can be presumptively identified as Clostridium perfringens. The enzyme producing the outer zone of hemolysis is:

Lecithinase

The beta hemolysis seen around the opaque, flat, spreading colonies illustrated in this photograph of a 5% blood agar plate is helpful in differentiating Bacillus cereus (hemolytic) from Bacillus anthracis (not hemolytic). Each of the following characteristics is also helpful in differentiating these two species EXCEPT:

Lecithinase production

A gram-negative rod from a stool culture produces red colonies with black centers on xylose lysine decarboxylase (XLD) agar. When the organism is inoculated to triple sugar iron agar (TSIA) and lysine iron agar (LIA), it should appear as which of the sets of tubes shown in the image?

Left

The Gram stain of a sputum specimen is unremarkable but the culture reveals many small gram-negative rods that are able to grow only on charcoal yeast extract agar. What is the MOST likely diagnosis?

Legionnaire's disease

A group of Canadian travelers was visiting the island of Kauai in Hawaii for a summer vacation. They noticed a cave in the middle of the island that contained a 10 ft deep pool of water. Much to their surprise, they were the only individuals enjoying this newly discovered swimming hole. A few days later, all swimmers became ill. Their physician believed they all had Weil disease. Which of the following organisms can cause this disease?

Leptospira interrogans

Which of the following infections is caused by Chlamydia trachomatis?

Trachoma, a major cause of preventable blindness in the world.

Which spirochete is a causative agent of human disease and is acquired through contact with the urine of carrier animals?

Leptospira interrogans sensu stricto

Based on the results of in-vitro susceptibility testing, patients with septicemia from each of the bacterial species listed below can potentially be treated with vancomycin EXCEPT:

Leuconostoc species

The colonies growing on the surface of a thiosulfate citrate bile sucrose (TCBS) agar plate (the green color indicates lack of sucrose fermentation) were identified as Vibrio vulnificus. The serious complication of infections with this bacterial species is:

Life threatening septicemia

A tech is interpreting a urine culture from a catheter as the source. There is 1 colony of Staphylococcus epidermidis present on the blood agar which was streaked with a 0.001 loop. What should the tech do next?

List S. epidermidis as a possible contaminant

A tech is working on a urine culture and finds the following isolate: Escherichia coli: 5,000 CFU/mL How should the tech continue with the culture workup?

List the E.coli as a possible contaminant

Molecular methods can identify the presence of methicillin-resistant staphylococcus aureus (MRSA) in patient specimens by detecting different species-specific genes. All of the following are species-specific genes in detecting MRSA EXCEPT?

van A

Performing quantitative cultures on bronchoalveolar lavage and protected brush specimens are better than performing routine semi-quantitative cultures because in quantitative cultures there should be which of the following?

Low numbers of contaminating normal respiratory flora and colonizing organisms and higher numbers of potential pathogens.

Which of the following culture media should be used to attempt to recover mycobacteria from a clinical specimen?

Lowenstein-Jensen (LJ) medium

Erythema migrans, spirochetemia, and chronic arthritis are three stages in the progress of:

Lyme disease

Which of the following substances produced by Group A Streptococci is responsible for producing type specific immunity?

M antigen

All of the following are virulence factors utilized by Streptococcus pneumoniae to evade host defenses when causing meningitis, EXCEPT: Pericarditis may occur as a complication from endocarditis caused by Staphylococcus aureus. Virulence mechanisms attributed to the spread of this organism include all of the following EXCEPT:

M protein

Beyond direct detection, what molecular method listed below is being widely used in clinical laboratories across the United States and allows for rapid detection of a bacteria from an isolated colony? A microbiology laboratory recently purchased a rapid identification instrument that uses a laser on the microorganisms, which produces an ion cloud. These ions are then separated in a tube and travel within the tube to a detector. The time of travel will be measured and a mass spectrum will be produced. Which of the following techniques uses this methodology?

MALDI-TOF

Which of the following scenarios represents appropriate detection of MRSA by the Kirby Bauer method?

MHA; direct colony suspension; 35oC; cefoxitin disk; 18 hour incubation

Matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) is used for the identification of aerobic bacterial isolates on a urine culture bench. Upon placing the target into the MALDI-TOF instrument, no peaks were found on any target spots, including the quality control. What caused this issue?

Matrix solution was not added to the target wells

Illustrated in this photograph is an agar plate on which an unknown species has been inoculated. A 5 µg novobiocin disk (NB), a 100 µg furazolidone disk (FX), and a 0.04 µg bacitracin (A) disk had been applied immediately after inoculation of the plate. Based on the pattern of the zones of inhibition to these three antibiotics, the most likely identification is:

Micrococcus luteus

When performing sequence-based analysis to identify a bacterial isolate, all of the following must occur to ensure accurate results are obtained EXCEPT?

Mixed cultures can be used as specific sequence is being identified

Sequence-based testing is most useful in identifying which of the following organisms?

Mycobacterium

Which organism is a cell wall deficient bacterium that commonly causes primary atypical or "walking pneumonia?"

Mycoplasma pneumoniae

Neisseria species can be traditionally differentiated by their fermentation of sugars. Identify the biochemical reaction that goes with the correct species of Neisseria given.

N. meningitidis = Glucose +, maltose +, lactose -

The nitrate reduction test is used to determine the ability of an organism to reduce nitrate. The Enterobacteriaceae group can reduce nitrate. Based on this test, what is the end product for which nitrate is reduced?

N2

Routine culture methods in microbiology rely on the principles of bacterial cultivation and identification. Molecular testing, however, relies on the detection and manipulation of nucleic acids, allowing the microbial genes to be detected instead of the analysis of microbial products (e.g. enzymes, toxins, or identifiable characteristic growth of an organism). One disadvantage to doing molecular testing is?

Need for dedicated space and equipment

From the list of organisms below, identify the most likely species based on this image of a gram stain from a male urethral swab. A joint fluid was received in the microbiology laboratory. The specimen was cloudy and many neutrophils with intracellular and extracellular Gram-negative diplococci were seen on the Gram stain. The specimen was inoculated to sheep blood and chocolate agar and grew a small, grayish-white colony on chocolate with no growth observed on the sheep blood. Which of the following is most likely the organism? A Gram-negative diplococci grows on MTM (Modified Thayer Martin), is oxidase positive and superoxol positive. The carbohydrate utilization reaction seen in the QuadFerm system shown in the image provides an identification of which of the following organisms? Sexually active women can develop peritonitis in the form of perihepatitis, inflammation of the liver surface, due to which of the following organisms? The Thayer-Martin agar plate seen in this illustration exhibits marked growth. The most likely organism found here would be:

Neisseria gonorrhoeae

A gram-negative diplococcus is isolated from a throat culture. The isolate grows on Thayer-Martin agar, produces acid from maltose, lactose, and glucose and is ONPG positive. What is the most likely identification of this isolate?

Neisseria lactamica

Gram-negative cocci that occur in pairs with their adjacent sides flattened, giving them a "coffee bean" appearance (indicated by the arrows in the image), are typical of which of the following bacteria? The oxidase test is used to presumptively identify which of these organisms?

Neisseria spp

Specimen handling from patients with symptoms consistent with tularemia requires work in a biological safety cabinet. Although PCR may confirm infection with Francisella tularensis, the following culture characteristics and tests aid in presumptive identification:

No growth on MAC, slow growth on CHOC; oxidase negative, positive catalase and ß-lactamase

The colonies observed in the upper image on the right are non-pigmented and dry to chalky. They were recovered from an expectorated sputum sample of an immunocompromised 70-year-old man with pneumonia. The Gram stain shown in the lower image to the right depicts delicate, branching bacilli. Based on this information, what is the most likely identification of this pathogen?

Nocardia asteroides

Light yellow, wrinkled, hemolytic colonies resembling an aerobic actinomycetes were observed on sheep blood agar. The gram stain, showing gram-positive bacilli, with branching, beaded rods were seen. Key to the identification is the hydrolysis of casein, as seen in the lower photograph. Acetamide was not hydrolyzed. The presumptive identification is: Which of the following organisms is a cause of cutaneous infections?

Nocardia brasiliensis

Examine the Oxidation and Fermentation media images to the right. The image labeled as Bucket A represents what type of organism?

Non-utilizer

A CSF specimen was sent to the laboratory for analysis. A glucose, protein, and cell count were performed. Based on the following results, what would be the probable cause? AnalyteResultGlucose50 mg/dLProtein25 mg/dLLeukocytes2 cells/mm3

Normal CSF

In the Escherichia coli 0157:H7 serotype. The 0157 portion of the serotype refers to which of the following?

O somatic antigen

Which of the following is the first step in the four steps of Koch's postulates?

Observe the same organism in all cases of a given disease

The colonies growing on blood agar, illustrated in the top image, are small, convex, entire, smooth, and light-yellow pigmented. Gram stain revealed short gram-positive bacilli arranged in loose clusters. The key to the identification is the positive lecithinase activity on egg yolk agar (lower image). Catalase and oxidase reactions were found to be positive and acid was produced from most carbohydrates. This is a soil organism occasionally causing nosocomial infections related to exposure to contaminated water. From these observations, select the presumptive identification of this isolate.

Oerskovia xanthineolytica

Which one of the following results is typical of Campylobacter jejuni?

Optimal growth at 42C

Which of the following tests would be most useful in the identification of Streptococcus pneumoniae?

Optochin

A 25-year-old female patient suspects of having an urinary tract infection (UTI) and presents to her doctor for a check-up. Her urine specimen is slightly turbid and the chemical and microscopic urinalysis results are as follows: Specific Gravity1.009Glucose0pH8Protein1+WBC15/hpfRCS1/hpfCrystalsNoneCasts2 hyaline/hpfEpithelial cells0/hpfBacteria2+ What should her doctor do next?

Order a culture and sensitivity

What is one of the BIGGEST challenges with isolating Francisella?

Organism growth is slow

The following is the BEST test to differentiate between Aeromonas hydrophila and Escherichia coli from a wound culture:

Oxidase production

A physician called the microbiology laboratory and asked what he needed to order to quickly diagnose Bordetella pertussis from a child who had what appeared to be having whooping cough. Which of the following should the physician be told to order?

PCR testing

Of the Enterobacteriaceae listed below, which of the following species fails to decarboxylate lysine, ornithine, and arginine?

Pantoea agglomerans

All of the following organisms are considered select agents for a bioterrorism event, EXCEPT? The FilmArray meningitis/encephalitis panel is a multiplex panel that detects all of the following microorganism types, EXCEPT?

Parasites

Infections of the bone marrow are not only caused by bacteria and fungi, they can be caused by viruses as well. Which of the following viruses can often be isolated from bone marrow specimens?

Parvovirus B19

The upper image of a blood agar plate illustrates the smooth, gray, nonhemolytic colonies that were recovered after 36 hours incubation from a wound of the forearm of a 14-year-old boy following a dog bite. The colony had a musty or mushroom odor and is oxidase positive. It did not grow on MacConkey agar. The lower image illustrates the gram stain prepared from the colony. The most likely identification is: The colonies illustrated in the upper photograph, recovered from a cat bite skin lesion of a child, reveal good growth of entire, convex, gray-white, smooth colonies on blood and chocolate agars. The colonies on blood agar are non-hemolytic and growth was not observed on MacConkey agar. Coccoid to rod-shaped Gram-negative bacilli are observed in the Gram stain. Positive tube reactions for indole, Voges Proskauer, ornithine, arginine, and strong production of esculin are observed in the lower photograph. The cytochrome oxidase reaction is also positive. With these observations, select the best choice for the identification of this isolate.

Pasteurella multocida

Matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) is used for the identification of aerobic bacterial isolates on a urine culture bench. Upon placing the target into the MALDI-TOF instrument, no peaks were found on one of the patient samples (out of 20 patients). The quality control passed. What caused this issue?

Patient sample was not added to the well

All of the following patients may submit an urine specimen from an indwelling catheter EXCEPT?

Patient seen for an annual physical

Illustrated in the upper photograph is the growth of off-white, convex colonies with internal flecking after anaerobic incubation for 48 hours on anaerobic blood agar. Beta hemolysis is not observed. The colonies were recovered from a uterine cervix specimen obtained from a 30-year-old female with postpartum endometritis. The gram stain reveals small gram-positive cocci arranged in short chains and pairs. A spot indole and catalase test were negative. From these observations, select the presumptive identification of this isolate.

Peptostreptococcus anaerobius

A tech is working on a urine culture and finds the following isolates: Escherichia coli: >100,000 CFU/mL Staphylococcus epidermidis: 5,000 CFU/mL How should the tech continue with the culture workup?

Perform sensitivity on E. coli and list the S. epidermidis as a contaminant

Which of the following describes the flagella on the bacterium in image B?

Peritrichous

Enterococcus spp. are commonly resistant to all of the following antimicrobial drug types EXCEPT:

Phenicols

Immunosuppressed or diabetic patients with ketoacidosis may present with symptoms of a brain abscess caused by which of the following?

Phycomycosis

Based on the picture and the criteria below, how would the Gram stain be interpreted? Host cells and background materialpink | blueSmear thickness1 cell thick or > 1 cell thickPrecipitated stainyes | noWould this field be appropriate for reading?yes | no????

Pink, 1 cell thick, No, Yes

An 85-year-old female nursing home patient was treated empirically with a cephalosporin for a urinary tract infection but later failed therapy. The physician then requested a culture and sensitivity on a new urine specimen that grew >100,000 CFU/mL of Escherichia coli. After reviewing the Kirby-Bauer disc susceptibility plate and susceptibility interpretations, what is the resistance mechanism (if any) for this organism?

Plasmid-mediated AmpC

A nitrate test is performed on a glucose nonfermenter. When the nitrate reagents were added, no color change occurs. When zinc dust was added, no color develops. How should this test be reported?

Positive for molecular nitrogen and negative for nitrite production

Illustrated in the photographs are smooth, entire, gray-white colonies growing on blood agar that are faintly beta-hemolytic (left). Light pink-red pigmented entire, smooth colonies grew on MacConkey agar (right). These isolates were recovered from a skin infection incurred by a 28-year-old man after swimming in a lake. The pink-red pigmentation of colonies on MacConkey agar suggests lactose fermentation. Biochemical reactions included Acid/Acid KIA reactions indicating fermentation of glucose. Oxidase was positive. Other positive reactions include indole, DNAse, and esculin. Additional biochemical tests identified this isolate as Aeromonas species. The pink-red colonies growing on MacConkey may suggest one of the Enterobacteriaceae. Which of the following choices will exclude this possibility?

Positive oxidase reaction

Rothia mucilaginosa is a member of the family Micrococcaceae that has been associated with endocarditis in patients after a cardiac catheterization, as well as intravenous drug users. Which test listed below would be most helpful in making a species identification?

Presence of a capsule

A urine sample yielded a lactose-negative, Gram-negative bacillus on primary isolation. Biochemical testing showed the following reactions: Oxidase negative H2S positive Urea positive Phenylalanine deaminase positive The organism which most closely fits this profile belongs to the genus: A urine sample yielded a lactose-negative, Gram-negative bacillus on primary isolation. Biochemical testing showed the following reactions: Oxidase negative H2S positive Urea positive Phenylalanine deaminase positive The organism which most closely fits this profile belongs to the genus:

Proteus

A tech receives a call from the floor regarding antimicrobial therapy. The patient culture yielded an aerobic Gram-positive coccus and the physician would like to use an antibiotic that inhibits RNA synthesis. Which of the following antibiotics would be the best choice?

Rifampin

Each of the following statements regarding Rickettsiaceae is correct EXCEPT:

Rocky Mountain spotted fever is almost always geographically restricted to the Rocky Mountain region.

Illustrated in the photograph of the blood agar plate are slow-growing colonies after 72 hours incubation that are pink-white, appear dry, and heaped in areas of confluent growth (arrows). They were recovered from a tooth abscess of a 14-year-old boy. Gram stain reveals short gram-positive bacilli that characteristically are in a diphtheroidal arrangement. Key characteristics to provide a definitive identification include positive reactions for catalase, nitrate reduction, esculin, and pyrazinamidase. Based on these observations, select the presumptive identification of this isolate.

Rothia dentocariosa

Sequence-based analysis is an alternate method used to identify bacteria and fungal isolates. This methodology uses rRNA genes (rDNA) and their intergenic regions as common target sites to identify these organisms. Which of the following rRNA gene target sites is used to identify bacterial isolates?

16s rRNA

The photograph illustrates a classic case of scrofula infection, most commonly caused by Mycobacterium scrofulaceum. The age range when this condition is most likely to appear is:

18 months- 7 years

Which of the following statements is true about the emergence of penicillin-resistant strains of Streptococcus pneumoniae?

A zone size of = 20 mm with the oxacillin disk screen must be confirmed with an MIC method to determine if Penicillin is susceptible or resistant.

An Enterobacteriaceae grows as a clear colony on MacConkey but a salmon-colored colony with a black center on Hektoen enteric agar. Which of the following TSI reactions would match these morphologies?

A/A H2S

Which two of the following tests are helpful for documenting previous streptococcal throat and skin infections?

ASO titer & anti-DNase B

When an unknown member of the Enterobacteriaceae family is recovered in primary culture, which key characteristics would lead you to suspect Klebsiella pneumoniae?

Absence of motility

Illustrated in the left tube of this photograph is a positive Voges Proskauer reaction (left tube). The red pigment is produced from the reactions of:

Alpha naphthol with diacetyl

A patient is being treated with gentamicin for a Gram-negative bacterial infection. The chemistry department has repeating peak and trough orders on the patient. Which of the following antibiotic classes does gentamicin belong to?

Aminoglycosides

Which of the following antibiotics inhibits protein synthesis by binding to the 30S ribosomal subunits and provides coverage against Gram-positive and Gram-negative aerobes?

Aminoglycosides

The clinical Gram stain taken from an endocervix revealed many WBC's with both intracellular and extracellular gram-negative diplococci. The specimen was plated onto a Modified Thayer-Martin plate and incubated. Following incubation, colonies resembling Neisseria gonorrhoeae were inoculated into separate CTA tubes containing glucose, lactose, sucrose, and maltose. The fluorescent monoclonal antibody test was positive as well as the CTA maltose and glucose tubes. What is the most appropriate next step?

Analyze another maltose tube using a known strain of Neisseria gonorrhoeae

Which of the following is only observed in Salmonella infections and not in Shigella infections?

Animals serve as a reservoir of infection.

A tech receives a request for MRSA/MSSA colonization testing on a patient in the hospital. Which of the following is an appropriate area of the body for culture for screening?

Anterior nares

Septic arthritis can be caused by Neisseria meningitidis, Streptococcus pyogenes, and Streptobacillus moniliformis. Diagnosing these organisms from joint fluid can be difficult because they may not grow in culture. Which of the following contributes to the cause of non-culturable septic arthritis?

Antigen/Antibody complexes accumulate in the joint

Illustrated growing on the surface of the blood agar plate shown in the upper left image are small distinctly beta-hemolytic colonies suggestive of beta-hemolytic streptococci, particularly when specimens are obtained from patients with an upper respiratory infection. Gram-positive bacilli in branching and Chinese letter formations are observed on Gram stain as illustrated in the upper right image. Observe the reverse CAMP reaction in the lower image. From these observations, select the identification of this bacterial isolate. In patients who present with a classic "strep throat", the beta-hemolytic, catalase-negative, Gram-positive bacillus that must be included in the differential diagnosis is:

Arcanobacterium haemolyticum

The infectious diseases listed below are listed with the most commonly associated bacterium, EXCEPT:

Aspergillus niger - "Black lung"

A 70-year-old man who three days previously had incurred a cerebral vascular accident was semi-comatose and having difficulty breathing. He developed a sudden fever overnight and was found to have pneumonia. The Gram stain shown in this photomicrograph was obtained from purulent material obtained through the intubation tube.

Aspiration pneumonia

A clean-catch midstream urine specimen from a 30-year-old woman was sent to the microbiology laboratory for culture. The patient had no urinary symptoms, but the urine culture grew out 100,000 CFU/mL of Escherichia coli from two cultures collected 24 hours apart. Which of the following categories would the patient be classified?

Asymptomatic bacteriuria in female patients

All of the following are Lancefield carbohydrate antigens found on beta-hemolytic Streptococcus species. All of the following antigens are found on organisms from the Streptococcus anginosus group EXCEPT?

B

Which of the following instrument-based systems are considered a continuous monitoring system?

BACTEC

Although an uncommon isolate in most microbiology laboratories, this bacterial species is included in the microbiota of the mouth and intestinal tract. The colonies on blood agar are irregular in size, smooth, non-hemolytic, entire, convex, and ranging from gray-white to light yellow. Distinctive is the "dog bone" appearance of branching Gram-positive bacilli as illustrated in this photomicrograph of a Gram stain. Biochemical activity is limited to fermentation of glucose and lactose. With these observations, select the presumptive identification.

Bifidobacterium species

Streptococcus pneumoniae can BEST be differentiated from the viridans group of streptococci by which characteristic?

Bile solubility

A tech working in the laboratory receives a VRE screening culture. Which of the following agars should the tech use to set up the VRE screening culture?

Bile-esculin-azide (BEA) agar with vancomycin

Which culture medium is specifically formulated to recover Salmonella typhi from stool specimens?

Bismuth sulfite agar

The preliminary identification of bacterial species often is made based on the odor produced by colonies recovered on primary isolation media. Which of the following odors would be expected for Eikenella corrodens?

Bleach

The tech in microbiology receives a call from the ER where the doctor suspects a patient has GI anthrax. What should the tech indicate is a proper specimen for collection to detect GI anthrax?

Blood

Since Brucella species are facultative intracellular organisms that infect the reticuloendothelial system, specimens of choice for recovery include:

Blood and bone marrow

Each of the following bacterial species is commonly associated with wound infections following a dog bite except?

Bordetella bronchiseptica

The pair of nonfermentative gram-negative bacilli producing the motility reactions illustrated in the left (motile) and right (nonmotile) tubes respectively shown in the photograph are:

Bordetella bronchiseptica and Acinetobacter baumannii

An aerobic Gram-negative coccobacillus was isolated from a nasopharyngeal swab 48 hours after culture from a 6-month-old with the following culture characteristics on Bordet-Gengou agar: Small zones of beta-hemolysis Urease: positive (24 hours) Oxidase: negative Motility: negative The MOST probable identification of this isolate is:

Bordetella parapertussis

A gram-negative coccobacillus produces small gray colonies surrounded by a zone of hemolysis on potato-blood-glycerol agar. The organism also grew on chocolate agar, but NOT on sheep blood agar. This is MOST likely to be which organism?

Bordetella pertussis

Which of the following growth factor(s) is necessary for the proper culture of Haemophilus influenzae?

Both X and V factors`

A cancer patient was admitted to the hospital with fever, tachycardia, and a drop in blood pressure. Due to the patient being treated for cancer, her chemotherapy had been administrated through an intravenous catheter. To rule out a catheter-related infection, the physician ordered two sets of blood cultures with one set being collected from the catheter site and the second set being collected by venipuncture. After 48 hours, the patient had positive blood cultures that grew Staphylococcus epidermidis. How will the physician know if the Staphylococcus epidermidis present is due to an infected catheter or is a contaminant?

Both blood culture sets (catheter and venipuncture) will be positive

The best clinical specimen for the recovery of Legionella pneumophilia is:

Bronchial washings

The recovery of Mycoplasma hominis from the genital tract of females has been associated with all of the following clinical syndromes EXCEPT:

Bronchitis

A 33-year-old livestock farmer, native to central Illinois, gave a one month history of diurnal fever, peaking in the evening and during the night, but subsiding during the daytime. He also complained of muscle aches and easy fatigability. After several negative blood cultures, an organism was finally recovered after 9 days incubation. The colonies shown in the upper photograph appeared on chocolate agar after 48 hours incubation in CO2. Growth was poor on blood agar. The Gram stain prepared from one of the colonies is shown in the lower photomicrograph. The most likely identification is:

Brucella abortis

The following statement is true regarding hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) and community-associated MRSA (CA-MRSA)?

CA strains tend to be associated with the PVL gene and skin and soft tissue infections.

Spinal fluid cultures on a 3-day-old infant revealed beta-hemolytic, gram-positive cocci occurring in pairs and chains. The organism was catalase-negative and bile esculin-negative. Resistance to bacitracin was noted. The other test necessary to identify this organism is a positive test by:

CAMP

Any media that supports the growth of Enterococcus species can be used to recover Vancomycin-Resistant Enterococci. However, to improve the recovery of VRE, selective media for VRE will provide the best sensitivity. Which of the following media is most helpful in recovering VRE from surveillance cultures?

CHROM VRE agar

Any media that supports the growth of Staphylococcus aureus can be used to recover Methicillin-Resistant Staphylococcus aureus (MRSA). However, to improve the recovery of MRSA, selective media for MRSA will provide the best sensitivity. Which of the following media is most helpful in recovering MRSA from surveillance cultures?

CHROMagar MRSA agar

For an isolate of Escherichia coli, Klebsiella, or Proteus species testing positive for ESBL (Extended Spectrum Beta Lactamases), all of the following antibiotics should be reported as resistant except: Methicillin-resistant Staphylococcus aureus (MRSA) is a serious health concern in the hospital environment and also in the community for patients who have had no contact with the healthcare setting. In order to control the spread of MRSA and prevent infection with the organism, it is recommended to screen patients for MRSA prior to being admitted to a healthcare setting. Which of the following antimicrobials is best to use when testing for methicillin resistance?

Cefoxitin

A patient grew out a Staphylococcus lugdunensis and after susceptibility testing, the isolate gave results indicating probable resistance to oxacillin. Which of the following is the best method to detect the mec-A gene to determine if the organism has true oxacillin resistance?

Cefoxitin disk diffusion

Which of the culture media listed is selective for the isolation of Yersinia enterocolitica in stool samples?

Cefsulodin-Irgasan-Novobiocin (CIN)

This isolate, identified as Enterobacter cloacae, was recovered from the urine and blood cultures of a patient who had recently returned from India where he had received a total hip replacement. He presented to the ED with multiple decubiti, sinusitis, and a urinary tract infection. The Hodge Test that was performed on this organism was negative. What resistance mechanism may be identified from the KB plate and the susceptibility interpretations?

Chromosomal AmpC plus Porin Mutation

Based on the reactions observed in the tubes shown in the photograph (including open and closed OF dextrose and a positive nitrate reaction only after the addition of zinc dust, as shown in the right tube of the pair labeled "Nit"), the most likely identification is: Which of the following can produce indole?

Chryseobacterium spp.

A tech receives a call from the floor regarding antimicrobial therapy. The patient culture yielded an aerobic Gram-negative bacillus and the physician would like to use an antibiotic that inhibits DNA synthesis. Which of the following antibiotics would be the best choice?

Ciprofloxacin

This member of the Enterobacteriaceae was isolated from a stool specimen and gave the following biochemical reactions: TSI: K/A, no gas, no H2S Citrate: Positive Lysine decarboxylase: Negative Ornithine decarboxylase: Positive Indole: Negative This organism agglutinated in Group D Shigella antiserum. All of the above biochemical results are consistent with this identification, EXCEPT?

Citrate

Illustrated in the photograph is a citrate tube. Sodium citrate is converted into alkaline products by bacteria that can utilize citrate as the sole source of carbon, giving a blue color from the conversion of the bromothymol blue indicator. Select the species of Enterobacteriaceae that produces this reaction.

Citrobacter freundii

Eikenella corrodens is associated with which of the following?

Clenched fist infection

A body fluid was sent to the microbiology laboratory for culture and after 48 hours of non-CO2 incubation, a small catalase-positive, non-spore-forming, diphtheroid-shaped Gram-positive rod grew on sheep blood agar. This organism was considered to be a possible contaminant since this organism is part of the normal skin microbiota. Which of the following organisms grew in the body fluid? Which one of the following organisms is commonly cultured from the nasopharynx of healthy people but is RARELY pathogenic?

Corynebacterium spp

Each of the bacterial species listed below are correctly matched with its identifying characteristic, EXCEPT:

Corynebacterium urealyticum - urease negative

The image shows an antimicrobial susceptibility result for a Corynebacterium species on a 5% sheep blood agar plate. The zone around the 10 µg penicillin disk rules out:

Corynebacterium ureolyticum

Which of the following organisms causes Q fever?

Coxiella burnetii

Which statement about bacterial culture for Clostridioides (Clostridium) difficile is TRUE?

Culture on appropriate media provides an effective means of recovering the organism.

The Carba NP confirmatory test is used to detect all of the following carbapenemases EXCEPT?

ESBL

Each of the tests below is appropriately matched with a chemical responsible for producing a positive result, EXCEPT:

Each of the tests below is appropriately matched with a chemical responsible for producing a positive result, EXCEPT:

Illustrated in this photograph is a close-in view of colonies growing on the surface of xylose lysine deoxycholate (XLD) agar. The bacterial species most likely producing the colonies shown here is:

Edwardsiella tarda

Which two antibiotics are used to confirm the presence of carbapenemase production in Enterobacteriaceae?

Ertapenem and Meropenem

All of the following are characteristics of Burkholderia pseudomallei, EXCEPT?

Fat, gram-positive rod

Each of the following characteristics will differentiate between Listeria monocytogenes and Erysipelothrix rhusiopathiae except:

Fermentation of glucose

The image shows a variety of colony elevations. Which colony elevation description matches with figure B in the image?

Flat

What is the methodology used for detecting the presence of bacteria in blood samples that are loaded onto a BACTEC analyzer?

Fluorescent change

Blood specimens are typically sterile; however, if an organism is suspected, a peptide nucleic acid probe (PNA) FISH can be used to identify the organism directly from the specimen. Which of the following microscopes can be used to examine PNA FISH slides?

Fluorescent microscope

Which bacterial genus contains fastidious, facultative intracellular, gram-negative bacilli that causes a zoonosis called tularemia?

Francisella

Illustrated in this photograph is a blood agar plate inoculated with a beta-hemolytic streptococcus obtained from a throat culture of a patient with acute pharyngitis. A 0.04 µg bacitracin (left) disk and an SXT disk (right) had been placed in the areas of streaking. The reactions observed allow the most likely presumptive identification of a streptococcus belonging to the Lancefield group:

Group A

Which one of the following organisms is sensitive to bacitracin:

Group A streptococcus

A positive CAMP reaction and hippurate hydrolysis are key in identifying which beta-hemolytic streptococci? A ß-hemolytic isolate on SBA revealed a Gram-positive coccus arranged in chains. The isolate was catalase-negative, PYR negative, bacitracin resistant, and positive for CAMP and hippurate hydrolysis. What is the presumptive identification of this isolate?

Group B

A 30-year-old man with chronic persistent hepatitis developed an abscess in the right hepatic lobe. A needle aspiration revealed purulent material. The small colonies shown in the upper photograph were isolated after 36 hours of incubation at 35°C. They emitted a butterscotch odor. The lower photomicrograph reveals the gram stain features. The antigen most likely carried by this isolate is:

Group F

The appearance of small colonies, growing adjacent to large Staphylococcus aureus colonies on the surface of the sheep blood agar plate indicates the need for Factor V for growth (upper photograph). This is confirmed by the X and V Factor Test in which growth is observed only around the V impregnated strip, but not around the X filter paper disc. Factor X is included in the agar medium. With these observations, select from the multiple choices the name of this isolate.

Haemophilus parainfluenzae

Lysine iron agar is a less commonly used culture medium that is most helpful in the identification of:

Salmonella enteritidis

Infections with Eikenella corrodens is associated with:

Trauma associated with human teeth

Direct microscopic examination of a wet preparation of vaginal discharge provides the simplest rapid diagnostic test for which of the following organisms?

Trichomonas vaginalis

A cerebral spinal fluid was collected from a lumbar puncture to evaluate for possible meningitis. Four tubes were collected and sent to the microbiology laboratory for analysis. Which of the four tubes is preferred for microbiology studies?

Tube 2

A CSF specimen was sent to the laboratory for analysis. A glucose, protein, and cell count were performed. Based on the following results, what would be the probable cause? AnalyteResultGlucose50 mg/dLProtein100 mg/dLLeukocytes80 cells/mm3 mononuclear

Viral infection

A woman came to see her physician as she was having vaginal/vulvar itching and some pain upon urination. To obtain a diagnosis of a yeast infection, which of the following is the test of choice?

Wet preparation

The McFarland Comparison Card shown in the illustration is used to:

Standardize concentrations of organisms

A small gram-negative rod isolated from an eye grows on chocolate agar and it produces satellite growth around staphylococci colonies on sheep blood agar. The organism requires:

X factor and V factor

Shigella species generally exhibit which of these characteristics?

Nonmotile

Which one of these Gram-positive species has a high incidence of vancomycin resistance?

Enterococcus faecium

An alpha-hemolytic streptococcus isolated from a urine culture is resistant to optochin and bacitracin, grows in 6.5% NaCl broth, and is PYR positive. The organism is MOST likely: This non-hemolytic organism was isolated from the blood culture of a patient. The image shows the organism's reactions in 6.5% NaCl broth and on bile esculin agar. With further testing, this isolate will most likely be identified as: An alpha-hemolytic, catalase-negative, Gram-positive coccus from a wound culture gave these additional results: Bacitracin resistantBile esculin hydrolysis positiveCAMP negativeNa hippurate hydrolysis negativePYR positive Which of the following would be the MOST probable identification?

Enterococcus spp

The images represent a gram-positive, catalase-negative, non-motile coccus inoculated to bile esculin agar as seen in the top image. The organism grows in 6.5% NaCl broth and the reaction on 6 µg/mL of vancomycin in Mueller Hinton agar is shown in the bottom image. The organism should be reported as:

Enterococcus spp., Resistant to vancomycin

The gram stain image on the right is a vaginal smear obtained from an 11-year-old girl suspected of being the victim of sexual abuse. The appearance of intracellular gram-negative diplococci (GNDC), as seen in the segmented neutrophil at the tip of the arrow, can represent different organisms. Therefore, recovery of the bacterial species in culture and biochemical identifications is needed before the case can be resolved. Each of the following may appear as intracellular GNDC EXCEPT:

Gardnerella vaginalis

If a Brucella species is suspected in blood culture, it should be held for a maximum of how many days on a commercial blood culture system?

10-14

The black colonies growing on the surface of this cystine-tellurite agar plate, with dark brown halos surrounding the colonies, is one of the characteristics of: This micrograph is most consistent with the cell morphology of: The serum medium and methylene blue stain originally described by Loeffler are both helpful in the identification of: An uncommon laboratory isolate, the colonies on blood agar, as seen in the top upper frame of the composite image were cultured from the throat swab of a 10 year old girl presenting with a red throat and mucosal pseudomembrane. These tiny gray-white, non hemolytic colonies are non-descriptive. Distinctive are the black pigmented colonies as observed on Tinsdale agar (lower image in the top composite photograph). Illustrated in the lower composite photomicrograph (upper image) are slender gram positive bacilli. Bacilli with meta-chromatic granules are observed in a methylene blue stained microscopic mount (lower image). From these observations, select from the multiple choices the presumptive identification of this isolate

Corynebacterium diphtheriae

From the following organisms, which one is considered to be the LEAST pathogenic to humans?

Corynebacterium ulcerans

All of the following descriptions about Pasteurella species are true, EXCEPT:

Grows well on MacConkey agar

Which of the following is also known as the Koch-Weeks bacillus?

Haemophilus aegyptius

An eleven-year-old girl was seen in the emergency room with sudden onset of sore throat, fever, and dysphagia, the latter accompanied by an intermittent sensation of choking. The bacterial species shown in the upper photograph of a chocolate agar plate was recovered from a throat culture. The most likely bacterial species based on the test shown in the lower photograph is: Which of the following organisms would show as negative for the testing shown in the image? Satellitism observed in cultures is most commonly associated with which of the following bacteria? A joint fluid specimen was received in the microbiology laboratory. The specimen was cloudy with many neutrophils and Gram-negative coccobacilli were seen on the Gram stain. The specimen was inoculated to sheep blood and chocolate agar and grew a small, gray to tan colony on chocolate with no growth observed on the sheep blood. Which of the following is most likely the organism? The term "HACEK" is often associated with infective endocarditis. All of the following organisms are included in the "HACEK" group, EXCEPT? The colonies growing on blood agar (upper image) were recovered from a sinus aspirate from a patient with acute sinusitis. The large, Staphylococcus colonies are obvious; however, note the satellite growth of small colonies. Small, Gram-negative coccobacilli are observed in Gram stains. The pattern of bacterial growth around the X and V filter paper strips in the image to the right confirms these satellite colonies are Factor X and V dependent. From the list of multiple choices, select the name of this isolate. Illustrated in this photograph is the surface of a 5% sheep blood agar plate on which are growing colonies of yellow-pigmented Staphylococcus species. Note the tiny semi-translucent colonies that satellite around some of the colonies. Pleomorphic gram-negative bacilli were seen on gram stain. The most likely identification is: A 21-year-old female developed painful swelling of the left knee along with a low-grade fever. The knee was painful to palpation, an effusion was evident, and the overlying skin was slightly erythematous. Fluid was aspirated and a gram stain was performed (as seen in the images to the right). Based on the Gram stain morphology, which of the following bacterial species is LEAST likely to serve as the etiologic agent in the case described? A 42-year-old chain smoker experienced an increase in cough, sputum production, and intermittent shortness of breath for over one week. A diagnosis of chronic bronchitis with acute exacerbation was made. The image shows a Gram stain of an early morning, spontaneously expectorated sputum. Based on the pleomorphic coccobacilli shown in the Gram stain, what is the most likely cause of the exacerbation? This organism has been placed in trypticase soy broth and then streaked on a nutrient agar plate. Strips containing X, V, and XV were placed on the plate and it was incubated 24 hours in CO2 conditions. With this information and the picture to the right, what is the identification of this organism? Acute obstructive epiglottitis, both in adults and children, is most commonly caused by a specific bacterial species that can be recovered on chocolate agar and requires both hematin and NAD. The most likely identification is: All of the following organisms have been linked to causing endocarditis EXCEPT? A pediatric patient arrived at the doctor complaining of itching eyes that appeared red and slightly purulent. When a sample was submitted to the laboratory, the sample grew only on the chocolate plate as seen in the upper image. When performing a satellite test, the image on the bottom is observed. What is the most likely identity of the organism causing this patient's symptoms? In the image to the right, small, minute, colonies are growing around a colony of Staphylococcus aureus on sheep blood agar. Which of the following organisms is this a characteristic?

Haemophilus influenzae

The fastidious gram-negative bacillus, often producing pitting of the agar around the colonies growing on blood agar, as illustrated in this photograph, producing a bleach-like odor is most commonly associated with one or more of the following conditions:

"Clenched fist" infections of the hand

Which of the following is used to standardize the bacterial inoculum used in a disk diffusion test (Kirby-Bauer method)?

0.5 McFarland standard

A spinal fluid was sent to the laboratory for testing. When the hematology tech performed the cell differential, she noticed encapsulated yeast as seen in the images to the right. Upon further investigation, she determined that the patient was immunocompromised and had a recent history of pneumonia. Which of the following would be the most beneficial test to determine a diagnosis?

Cryptococcus neoformans antigen test

A positive RPR test and a negative FTA-ABS test is most likely the result of:

False-positive reaction

Which of the following conditions is associated with a typical Bacillus cereus infection?

Foodborne enteritis

Of the following organisms, which organism is known to cause bacterial vaginosis?

Mobiluncus spp

What color would the agar be around a colony of Staphylococcus epidermidis growing on mannitol salt agar (MSA)?

Red

Among the non-fermenters, which of the following is the only bacterial species to produce hydrolyze esculin?

Rhizobium radiobacter

What is the most common agent of infection in CSF shunts?

Staphylococcus

Throughout history, plague pandemics have killed millions. Transmission of the human plague may still occur through bites of rodent fleas or contact with infected animals. What is the causative agent of plague? A respiratory culture is submitted to the microbiology laboratory for testing. An organism displaying the following characteristics is recovered: Gram stain shows fat, Gram-negative rods in single or short chains that may demonstrate bipolar staining Faster growth at 25° C Gray-white, translucent colonies on sheep blood agar (SBA) at 24 hours that turn slightly yellow and opaque at 48 hours Irregular colonies that have a "fried egg" and/or "hammered copper" appearance after 48-72 hours Catalase positive Oxidase negative Urea negative Indole negative What is the most likely organism, based on these results? What bacteria is responsible for the bubonic plague? A 27-year-old man who had recently worked as a medical laboratory scientist on the Navajo Native American reservation presented to the emergency department with high fever, diarrhea, and prostration. Axillary lymph nodes were hemorrhagic and enlarged. A smear was prepared from a lymph node aspirate and many Gram-negative bacilli were noted. The bacilli demonstrated a marked bipolar staining reaction described as a "safety-pin appearance" with Wayson stain. What is the most likely identification of this organism? A tech is working on a culture from an aspirated lesion. The culture grows non-hemolytic colonies with flattened edges and raised centers, resembling a fried egg on blood agar. Gram stain of the colonies shows plump Gram-negative bacilli with bipolar staining. What is the likely identification of the organism?

Yersinia pestis

The photograph on the right illustrates the Rosco Diagnostica IMI/EDTA disk test and the bioMerieux MBL E test. Both tests are used to detect metallo beta-lactamase production. After viewing the results of these tests, does this organism produce metallo-beta-lactamase?

Yes

A laboratory recently purchased a continuous monitoring system for blood culture analysis. The system is able to detect CO2 production by growing organisms and as a result, will produce a color change in the sensor located at the bottom of the blood culture bottle. The instrument will detect this color change and alert the staff that a blood culture is positive for bacterial growth. Which of the following instruments uses this methodology?

bacT/ALERT

The organisms Klebsiella pneumoniae, Enterobacter cloacae, and Escherichia coli can produce carbapenemases due to which of the following genes?

blaKPC

A D-zone test is performed to determine if Staphylococcus aureus or Streptococcus agalactiae has an inducible resistance to clindamycin. This inducible resistance is due to which of the following mechanisms?

erm gene

Which strictly human pathogen causes chancroid, a highly contagious, sexually transmitted genital ulcer disease?

haemophilus ducreyi

Carbapenemases are produced by various organisms such as Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter species. Detecting the presence of carbapenemase activity in these organisms is important to prevent the spreading of resistant organisms. Which of the following methods is used to detect the presence of carbapenemase-producing organisms?

mCIM

Oxacillin resistance in clinical strains of staphylococci is confirmed by the detection of the _______ gene.

mecA

Sequence-based analysis is an alternate method used to identify bacteria and fungal isolates. This methodology uses rRNA genes (rDNA) and their intergenic regions as common target sites to identify these organisms. Which of the following rRNA gene target sites is used to identify fungal isolates?

28s rRNA

When a lumbar puncture is performed, what volume of spinal fluid is needed for optimal recovery of meningitis-causing organisms?

5-10 mL

When performing quantitative cultures from protected brush specimens, which of the following colony-forming units per milliliter indicates a true bacterial pneumonia?

>10^3 colony-forming units/mL

The parts of the prototypical bacterium in the image to the right are identified below. Which of the following is incorrectly identified?

A - cytoplasmic membrane

The upper photomicrograph illustrates a Gram stain of sputum obtained from a 55-year-old man with symptoms of bacterial pneumonia. The lower photograph represents the growth of inoculum from the specimen on 5% sheep blood agar, on which had been placed an optochin ("P") and a 1 µg oxacillin disk. After 18 hours of incubation at 37°C in 5% CO2, the zone around the optochin disk is 18 mm, and around the OX disk is 8 mm. The interpretation is that the organism is most likely:

A pneumococcus, penicillin-resistant

Many organisms have developed resistance to antibiotics. What mode of resistance has MRSA acquired?

Acquisition of new targets

A clean-catch midstream urine specimen from a woman was sent to the microbiology laboratory for culture. The patient had a history of dysuria, frequent urination, suprapubic pain, no fever, no flank pain, or any urinary symptoms in the last 4 weeks before her current episode. The urine grew out 1,000 CFU/mL of Escherichia coli. Which of the following categories would the patient be classified?

Acute, uncomplicated UTI in women

A clean-catch midstream urine specimen from a 57-year-old woman was sent to the microbiology laboratory for culture. The patient had a history of fever, chills, and flank pain upon examination. The urine grew out 10,000 CFU/mL of Escherichia coli. Which of the following categories would the patient be classified?

Acute, uncomplicated pyelonephritis

The organism Acinetobacter baumannii is known to have caused which of the following outbreaks?

Afghanistan and Iraq U.S. soldiers outbreak

The bacterial species commonly found in association with deep tissue actinomycosis is:

Aggregatibacter actinomycetemcomitans

The colonies illustrated in the upper photograph were recovered from the aspiration of nasal secretion from a patient with acute sinusitis. The 48 hour colonies on blood agar are relatively small, entire, white, and non-hemolytic. Colonies growing on chocolate agar are also small, smooth, and entire with light yellow pigmentation. On Gram stain, pale-staining, Gram-negative coccobacilli are observed, with a tendency to form long, narrow filaments. The lower photograph reveals tube reactions with a KIA: Acid/Acid and the oxidative utilization of several carbohydrates except for xylose and mannose. Nitrate reduction is positive and ornithine and arginine decarboxylases are negative. From the observations, select from the multiple choices the genus/species name of this isolate.

Aggregatibacter aphrophilus

Bacterial colonies often emit distinct odors associated with foods. Which organism produces an odor that resembles fresh apples? Illustrated in the image to the left are 3-day old colonies growing on blood agar. The colonies are gray and spreading, and a sweet, fruity odor is noted. Plump, Gram-negative coccobacilli are seen on Gram stain. This isolate belongs to the motile, non-fermenters with peritrichous flagella. Carbohydrate utilization is asaccharolytic. Nitrite reduction produces gas and citrate is positive. From the multiple choices, select the name of this isolate.

Alcaligenes faecalis (odorans)

From the choices listed below, select the biochemical reaction that excludes a bacterial isolate from the family Enterobacteriaceae.

Alk/Alk reaction on Kligler's Iron Agar

Pseudomonas aeruginosa is often used as a bacterial species for the quality control of Kligler iron agar. What is the expected reaction?

Alkaline slant/alkaline deep

With regards to identifying resistance in Enterococcus species, all of the statements below are true, EXCEPT:

All antibiotics on a gram-positive panel should be reported.

The well-circumscribed, ulcerating pustule illustrated in the upper photograph evolved over 8 days following direct contact with raw animal hides that had been shipped from Central Asia. The lesion began as a small papule, which progressively enlarged, ultimately ulcerated, and became covered centrally with a black eschar. The lower photomicrograph is a gram stain prepared from a colony that grew within 48 hours on blood agar. The most likely agent of this infection is:

Bacillus anthracis ("malignant pustule")

Which bacterial species is most likely represented by the spreading, gray-white, beta-hemolytic colonies with a "frosted glass" appearance as illustrated in the photograph? Illustrated in the upper blood agar plate are large, spreading, gray-white colonies with a buttery consistency and fimbriated edges. Each colony is surrounded by broad zones of beta hemolysis. The Gram stain in the lower image reveals long, box-car shaped, spore-forming Gram-positive bacilli. Lecithinase is produced on egg yolk agar. These findings are most consistent with a presumptive identification of which of the following?

Bacillus cereus

The colonies seen in the upper frame, grown after 48 hours of incubation aerobically at 35°C, and the accompanying Gram stain in the lower frame are of an organism uncommonly associated with human disease; however, this organism has been associated with septicemia, bronchopneumonia, osteomyelitis and other infections, particularly in intravenous drug users. What is the most likely identification of the organism?

Bacillus circulans

Which of the following organisms is considered a contaminant when isolated from blood cultures and is part of normal skin flora? All of the following Bacillus species would have a wide zone lecithinase reaction, EXCEPT?

Bacillus subtilis

Group A beta-hemolytic streptococci are best characterized by which of the following A mucoid alpha-hemolytic translucent colony suspected of being Streptococcus pneumoniae was isolated from a blood culture. All of the following are appropriate tests to make a presumptive or definitive identification of this organism EXCEPT?

Bacitracin sensitivity

Which of the following is a presumptive test for the identification of Lancefield group A Streptococcus:

Bacitracin susceptibility

All of the following are usually associated with Group A Beta Streptococci, EXCEPT?

Bacteremia

Which of the following is MOST often determined to be the cause of sepsis?

Bacteria

All of the following statements are associated with MALDI-TOF mass spectrophotometry used in clinical microbiology, EXCEPT?

Bacteria is amplified using a laser.

A CSF specimen is received from a patient with suspected meningitis. Positive Gram stain, along with the results shown here suggest what type of condition? Elevated WBC count Neutrophils predominant Marked protein elevation Marked glucose decrease Lactate level = 37 mg/dL

Bacterial meningitis

The organism that is a strict anaerobe, non-motile, gram-negative bacillus, occurring in abscesses and associated with peritonitis is MOST likely:

Bacteroides spp

The bacterial species most likely associated with bacillary angiomatosis is:

Bartonela henselae

A patient who was seen in the ED has symptoms consistent with cellulitis. A gram stain from the patient's blood culture revealed gram-positive cocci in pairs and short chains. Blood cultures grew an organism that was susceptible to a 0.04 unit disk of bacitracin. Other characteristics one would expect to see with this bacterial isolate include:

Beta hemolysis, negative catalase, negative CAMP, no growth in 6.5% salt

The following is the term used to describe the total clearing of the agar surrounding colonies on a blood agar plate as seen in this illustration:

Beta-hemolysis

Which of the following enzymes, produced by Staphylococcus aureus is responsible for preventing penicillin antibiotics from being effective?

Beta-lactamase

This species is the most commonly reported laboratory-acquired bacterial infection and must be handled in class II or higher biological safety cabinet. They are small gram-negative coccobacilli that are strict aerobes and will grow on Sheep Blood Agar and Chocolate agar. They are nonmotile, catalase, urease, and nitrate positive and most strains are oxidase positive. From the choices below, please select the organism matching the microscopic and biochemical reactions listed: Tiny Gram-negative coccobacilli were isolated on chocolate agar from a wound on a man who had been hunting wild boar. The microbiologist performed the following test: OxidasePositiveUreasePositiveMotilityNonmotileColony morphologySmall, nonhemolytic Which of the following species is most probable?

Brucella spp

A patient was admitted to the hospital for fever, chills, weight loss, headaches, and fatigue. The patient mentioned that he had cut his hand while hunting wild boar a couple of weeks ago. Blood cultures were received in the microbiology laboratory and several days later a bone marrow specimen on the patient was received. The blood culture was positive after 5 days and the bone marrow grew a small, convex, smooth colony after 48 hours on sheep blood and chocolate agar. A gram stain was performed and demonstrated small Gram-negative coccobacilli organisms. Which of the following organisms is the cause of infection for this patient?

Brucella suis

A patient with cystic fibrosis is admitted with a fulminant lung infection. A sputum culture grows a non-lactose fermenting, oxidase-positive, Gram-negative bacilli. It is pyocyanin negative, nitrate reduction variable, and it is arginine dihydrolase negative.

Burkholderia cepacia

Which bacterial species is most likely represented by the spreading, wrinkled, non-hemolytic colony appearance as illustrated in the photograph?

Burkholderia pseudomallei

The recovery of this bacterial species from diarrhea stool specimens requires the use of selective culture media such as Butzler selective media or Skirrow blood agar incubated at 42° C in an atmosphere of 5% oxygen, 10% CO2, and 85% nitrogen. Growth on Skirrow blood agar as illustrated in the upper image are confluent smooth non-hemolytic colonies growing along the streak line with lateral extensions (arrows). Slender, long branching, S-shaped Gram negative rods are observed on Gram stain, as observed in the lower image. Positive reactions for oxidase, indoxyl, and hippurate provide for a more definitive identification. With these observations, select the name of this isolate. An organism grew at 37° C and 42° C from a stool culture that was oxidase, catalase, and hippurate positive. This organism will be identified as: A small, microaerophilic, curved, gram-negative rod which was isolated from a diarrhea stool specimen gave the following results: Grew best at 42 ºCOxidase positiveResistant to cephalosporinSusceptible to nalidixic acidHippurate hydrolysis positive What is the MOST probable identification of this organism? A stool culture showing an increased number of fecal leukocytes would correlate with an infection of which of the following species? A small, microaerophilic, curved, gram-negative rod which was isolated from a diarrhea stool specimen gave the following results: Grew best at 42 ºCOxidase positiveResistant to cephalosporinSusceptible to nalidixic acidHippurate hydrolysis positive What is the MOST probable identification of this organism?

Campylobacter jejuni

Molecular methods are commonly used for the direct detection of organisms in clinical specimens. One specimen type that can be used is cerebrospinal fluid. This is important as patients who are immunocompromised can succumb to neural infections quite easily when compared to immunocompetent patients. Which of the following is an advantage of performing molecular testing on CSF patients?

Can detect viable and nonviable organisms

An immunosuppressed patient with a CSF shunt is exhibiting symptoms of a shunt infection. When performing a Gram stain, the organism observed in the image to the right is seen. What is the most likely identity of this organism?

Candida spp

A technologist subcultures a positive blood culture and notes the following characteristics on the isolated colonies displayed in the image below: Growth of non-hemolytic colonies with a ground-glass appearance, displaying a "Medusa Head", as indicated by the arrows Gram stain reveals a large, gram-positive rod with central and subterminal spores that do NOT swell the cells Catalase positive Non-motile What would be the MOST likely conclusion and action

Cannot rule out Bacillus anthracis, refer isolate to your Laboratory Response Network (LRN) Reference Laboratory

Which of the following organisms is indole negative?

Capnocytophaga canimorsus

Which Gram-negative organism can produce "gliding motility" on agar plates and is a primary cause of juvenile periodontitis? Human dog bite infections may be caused by each of the following bacterial species EXCEPT: A fusiform-shaped, Gram-negative, oxidase-negative bacillus that produces colonies with marginal finger-like projections was recovered from the oral cavity of a patient with periodontal disease. The most likely identification is:

Capnocytophaga ochracea

Observed growing on chocolate agar after 4 days of incubation are non-descript tiny, circular, smooth colonies. Growth on sheep blood agar is typically absent or minimal. In the Gram stain, as illustrated in the upper photomicrograph, thin, long fusiform Gram-negative bacilli are observed. This organism was isolated from a skin abscess at the site of a dog bite. The Kligler Iron Agar reaction was A/A indicating carbohydrate assimilation, with distinctive positive test reactions for dextrose, sucrose, and maltose. With these observations, select the identification of this isolate.

Capnocytophaga species

Which of the following is the primary virulence factor in Streptococcus pneumoniae?

Capsular polysaccharide

The following is the primary virulence factor produced by Streptococcus pneumoniae that prevents phagocytosis:

Capsule

Different species of Neisseria can be differentiated from each other by:

Carbohydrate utilization

The isolate is represented by the slow growing small, gray-white, opaque and non-hemolytic colonies on blood agar. Short, gram-negative bacilli are, lying singly but also in the form of characteristic "rosette-like" clusters (arrows) are observed in the lower photomicrograph. As additional biochemical reactions necessary to confirm a presumptive identification, oxidase and indole reactions are positive; catalase, nitrate and urease reactions are negative. Based on these observations, select from the multiple choices the presumptive identification of this isolate.

Cardiobacterium hominis

A tech is working with a small Gram-negative coccobacillus that may be Francisella tularensis. Which of the following tests could the tech use to rule out this organism?

Catalase negative

The irregular-sized, gray-white colonies, with irregular margins, as shown in the image to the left in the upper composite photograph, were recovered from a stool specimen in a case of antibiotic-associated colitis. The colonies are flat, gray-white, and spreading with irregular margins. Some patients with this infection develop pseudomembranous colitis that can be life-threatening. Growth is enhanced when Cycloserine-cefoxitin-fructose agar (CCFA) is used, as seen in the upper right photograph. The observation of elongated, gram-positive bacilli with distinctive subterminal and central spores in Gram stain mounts provides for presumptive identification. Additional key identifying reactions are the absence of lipase and lecithinase and a chartreuse pigment under fluorescence light. With these observations, select the presumptive identification of this isolate. A recto-sigmoidoscopy revealed pseudomembranes in a patient with severe diarrhea following prolonged treatment with ampicillin. Which of the following organisms is MOST likely to be isolated?

Clostridioides difficile

Which bacterial species listed is a select agent, which is capable of producing an extremely potent, lethal neurotoxin? Which of the following Clostridium spp. produces a toxin that is a potential bioweapon?

Clostridium botulinum

From the choices listed below, which organism is classified as an obligate anaerobe?

Clostridium novyi

The Gram stain shown in the image was prepared from a positive anaerobic blood culture bottle after 36 hours incubation. Based on the morphology of the bacterial cells (some with spores, noted by the blue arrows), what is the most likely identification? The following is a spore-forming anaerobe that is associated with neutropenic enterocolitis: The flat, spreading gray-white colonies with an outer zone of beta hemolysis as observed on the surface of an anaerobic blood agar plate shown in the upper image were recovered from a blood culture of an elderly man leading to a potential diagnosis of cancer of the colon. Observed in the gram stain are short gram-positive bacilli, some with distinctive central and sub-terminal spores. The organism is a lactose fermenter and produces DNAse. From these observations, select the most likely isolate.

Clostridium septicum

A 25-year-old man was experiencing some difficulty in chewing and swallowing food. He had incurred a deep laceration of the lower leg in a lawnmower incident one week before. The wound was healing but signs of infection persisted. The image shows the Gram stain of a spreading, gray colony isolated from an aspirate of the wound, incubated under anaerobic conditions. Three additional bacterial species were recovered on blood agar incubated aerobically. What is the most likely identification of this anaerobic organism?

Clostridium tetani

A CSF shunt tip specimen was sent to the microbiology laboratory for culture. The shunt specimen was inoculated to sheep blood agar, chocolate agar, and a thioglycollate broth. After 24 hours of CO2 and non-CO2incubation at 37°C, the sheep blood agar, chocolate agar, and the thioglycollate broth had growth. The microbiology tech evaluated the media and observed the following: Growth: Sheep blood grew small, white non-hemolytic colonies. Chocolate grew small, white colonies. Gram Stain: Gram-positive cocci in clusters Biochemical: Catalase positive; coagulase-negative Which of the following organisms is most likely the cause of the CSF shunt tip infection?

Coagulase-negative staphylococci

The most common cause of acute meningitis associated with CSF shunts is:

Coagulase-negative staphylococci

A patient was screened for possible methicillin-resistant Staphylococcus aureus (MRSA) by culturing the nares of the patient. All of the following media can be used to screen for MRSA EXCEPT?

Columbia agar

_______________ is predominantly associated with skin and soft tissue infections (SSTIs), such as abscesses, cellulitis, folliculitis and impetigo

Community-acquired MRSA

The disease most commonly associated with the novobiocin-resistant staphylococcus illustrated in this photograph is:

Community-acquired urinary tract infection

Which anaerobic bacteria incidence is increasing in CSF shunt infections? The colonies illustrated in the photograph on the surface of an anaerobic blood agar plate are relatively small, measuring 1 - 2 mm in diameter, round, smooth with a shiny surface, and are non-hemolytic. The Gram stain photomicrograph reveals small Gram-positive bacilli in short chains and loose diphtheroidal-like clusters. The indole reaction was found to be strongly positive. This isolate is part of the normal flora of the skin, nasopharynx, oral cavity, and gastrointestinal and urinary tracts. It is commonly recovered as a contaminant from blood cultures, but on occasion may be the cause of skin and shunt infections. From these observations, select the presumptive identification of this isolate. The colonies illustrated in the photograph on the surface of an anaerobic blood agar plate are relatively small, measuring 1 - 2 mm in diameter, round, smooth with a shiny surface, and are non-hemolytic. The Gram stain photomicrograph reveals small Gram-positive bacilli in short chains and loose diphtheroidal-like clusters. The indole reaction was found to be strongly positive. This isolate is part of the normal flora of the skin, nasopharynx, oral cavity, and gastrointestinal and urinary tracts. It is commonly recovered as a contaminant from blood cultures, but on occasion may be the cause of skin and shunt infections. From these observations, select the presumptive identification of this isolate. An anaerobe was recovered from a blood culture after 92 hours of incubation. A gram stain of the isolate is illustrated in the photomicrograph. The most likely identification is: A CSF shunt specimen was sent to the microbiology laboratory for culture. The shunt specimen was inoculated to chocolate agar and a thioglycollate broth. After two days of incubation in CO2 at 37°C, the chocolate agar had no growth and the thioglycollate broth had growth at the bottom of the tube. The microbiology tech then subbed the thioglycollate broth to an anaerobic blood agar plate and incubated the plate in anaerobic conditions at 37C for 48 hours. After the 48 hour incubation, the anaerobic blood agar plate was evaluated: Growth: Small, white colonies were observed Gram Stain: Gram positive, pleomorphic, diphtheroid-like rod Biochemical: Catalase positive; Nitrate Reduction positive, Sensitive to Vancomycin and Kanamycin Which of the following organisms is most likely the cause of the CSF shunt infection?

Cutibacterium (Propionibacterium) acnes

Which of the following is the best media for recovery and presumptive identification of Clostridioides (formerly Clostridium) difficile in suspected cases of pseudomembranous colitis?

Cycloserine-cefoxitin fructose agar (CCFA)

The following Clostridioides difficile virulence factor is significant in the cause of antibiotic-associated pseudomembranous colitis:

Cytotoxin A or B

Which serogroup of Neisseria meningitidis is no longer recognized?

D

What is the BEST method for the detection of Chlamydia trachomatis in cases of sexually transmitted disease (STD)?

DNA amplification techniques

Illustrated in this photograph are latex agglutination reactions of an unknown beta-hemolytic streptococcus recovered from a blood culture. Each reaction is labeled by the group number tested. Of the choices listed, which source is most likely the primary infection for the suspected organism?

Deep wound cellulitis

Which of the following statements is correct regarding the glutamate dehydrogenase (GDH) assay for Clostridioides difficile?

Detection of the GDH gene and 16srRNA genes for C. difficile without the presence of a toxin gene indicates a carrier or nonpathogenic state.

In order to speciate a swarming Proteus organism found on an eosin methylene blue (EMB) agar plate, the best approach would be to:

Determine indole production and ornithine decarboxylase

The laboratory test most commonly used to establish a definitive diagnosis of primary syphilis is:

Direct fluorescent antibody test

Bacitracin susceptibility testing is useful for:

Distinguishing staphylococci from micrococci

The use of molecular testing to identify the presence of Methicillin-Resistant Staphylococcus aureus (MRSA) is not always the best method because false-positive results can occur. However, the main purpose for performing molecular testing on surveillance cultures for MRSA is all of the following, EXCEPT?

Does not require culture confirmation

Illustrated in this photograph are colonies growing on the surface of a chocolate agar plate. The colonies were recovered from a subcutaneous infection of the forearm and had a bleach odor. The most likely identification is: The colonies illustrated on the blood and chocolate agar plates represent a slow-growing bacterial species that is endogenous in the oral cavity and upper respiratory tract. It may be recovered from human bite skin infections incurred during fistfights. Note the pitting of the agar surrounding the colonies growing in the chocolate agar plate. The Alk/Alk non-fermentative reaction seen in the Kligler Iron Agar tube to the left in the lower photograph indicates the non-fermentation of glucose, also indicated by the lack of carbohydrate assimilation in the individual carbohydrate reaction tubes to the right of the KIA tube. A reduction of nitrate is seen and decarboxylation of ornithine is also positive. Based on these observations, select from the multiple choices listed the correct identification of this bacterial isolate: Clenched-fist cellulitis is commonly found in patients who have been in a physical altercation. Which organism below is the most likely cause of this condition?

Eikenella corrodens

An organism has been isolated from the CSF of a premature newborn. The organism grew in 48 hours on MacConkey and blood agar (see image). Additional reactions include: Alk/Alk (red over red) on Kligler Iron agar, oxidative utilization of carbohydrates, and a positive indole reaction. Which of the following is the most likely identification?

Elizabethkingia (Flavobacterium) meningosepticum

Motility is a key initial assessment in the presumptive identification of the nonfermentative gram-negative bacilli. All of the following organisms are motile EXCEPT?

Elizabethkingia meningoseptica

Loeffler's medium is useful in making the presumptive identification of isolates suspicious for Corynebacterium diphtheriae recovered from oropharyngeal cultures because it:

Enhances granule formation as seen in methylene blue stains

Shown in this photograph are three tubes of Moeller decarboxylase broths, containing from left to right, the amino acids lysine, arginine, and ornithine respectively. A red-blue reaction indicates decarboxylation of the amino acid; yellow is negative. From the bacterial species listed, these reactions are most likely caused by: The reactions observed in the photograph to the right reveals a motile, gas producing, lactose fermenter that produces acetyl methyl carbinol in VP broth and has the ability to utilize sodium citrate as its sole source of carbon. The most likely identification is:

Enterobacter aerogenes

An unidentified colony was inoculated to the surface of a filter paper strip impregnated with cytochrome oxidase reagent (dimethyl-p-phenylenediamine dihydrochloride) as shown in the picture on the right. The family of bacteria ruled out by the reaction seen is:

Enterobacteriaceae

Which of the following Enterococcus species is motile, mannitol positive, pyruvate negative, and is a rare cause of clinical infections?

Enterococcus casseliflavus

This photograph shows a positive reaction in each of the tubes with the tube on the left containing esculin medium and the tube on the right containing heart infusion broth with 6.5% sodium chloride. The bacterial species that characteristically produces these reactions is: Illustrated in the photograph is a bile esculin agar plate inoculated with a bacterial isolate from a urinary tract infection. The most likely identification is: Which of the following is the most commonly encountered enterococcal species? The bile esculin test has been used to determine if an organism can hydrolyze esculin. Esculin fluoresces, so if it is not hydrolyzed, the tube will fluoresce (bucket B), but if it is hydrolyzed, no fluorescence is seen (bucket A). Which of the following organisms hydrolyzes esculin? The upper image is a photomicrograph of a Gram stain prepared from a positive blood culture obtained from a 68 year old female with an indwelling urinary bladder catheter. Smooth, gray, faintly beta hemolytic colonies were recovered in subcultures of the positive bottle. The tubes shown in the lower photograph are: an esculin slant (left) displaying intense brown coloration a 6.5% sodium chloride broth (right) showing cloudy growth The most likely identification is:

Enterococcus faecalis

A patient presents to the emergency room with hemorrhagic diarrhea. A stool specimen was sent to the microbiology laboratory for culture. The specimen was plated on blood agar, MacConkey (MAC) agar, and Sorbitol MacConkey (SMAC) agar. Gram-negative, oxidase-negative rods (bacilli) grew as lactose fermenters on MacConkey agar and clear colonies on Sorbitol MacConkey agar. Biochemical testing revealed the organism was lysine decarboxylase positive and did not produce hydrogen sulfide (H2S). Which organism is suspected?

Escherichia Coli possibly 0157:H7

All of the associations listed below between bacteria and their expected colony morphology on 5% sheep blood agar are correct, EXCEPT:

Escherichia coli - pink colonies

All of the following statements concerning biochemical reactions are true, EXCEPT:

Escherichia coli is positive for utilization of sodium citrate, as depicted in tube A.

To screen for the Methicillin-Resistant Staphylococcus aureus, all of the following collection sites are appropriate EXCEPT? When vitreous fluid is collected, it must be transported to the laboratory within 15 minutes and set up immediately for culture. This specimen type must be handled with care as this specimen type is not easy to obtain. What body site is this specimen collected from?

Eye

One of the key biochemical characteristics by which Escherichia coli serogroup O157 can be screened from stool specimens is?

Failure to ferment sorbitol

The well circumscribed cutaneous papule with the distinct outer erythematous border illustrated in the upper photograph developed over a period of 5 days at the site of a tick bite. The lower photograph illustrates colonies growing on a buffered charcoal yeast extract agar plate that had been inoculated with material from the ulcer bed three days before. Tiny, pale-staining Gram negative coccobacilli were seen on Gram stain. The most likely causative agent is:

Francisella tularensis

Agar plates on a positive blood culture are incubated for 48 hours and no growth is visible on the agar plates. The tech reviews the initial Gram stain from the blood culture bottle, which reveals tiny pleomorphic Gram-negative coccobacilli. What organism should the tech suspect and what should the tech do next?

Francisella tularensis; Sub blood culture bottle to a media with cysteine for optimal growth

A microbiologist was surprised when he could not recover Helicobacter pylori from gastric biopsies in which organisms were seen in the tissue sections. He was advised to switch from the Campy BAP selective medium to Skirrow's blood agar because the latter is:

Free of cephalothin

Observation of colonies on KVLB agar producing chartreuse fluorescence under a Wood's lamp allows for presumptive identification of which anaerobic bacterial genus?

Fusobacterium

The colonies illustrated in the top photograph are 48-hour-old colonies growing on the surface of blood agar that had been incubated anaerobically. The colonies are small, gray-white, and convex with irregular borders and internal flecking. Long, slender fusiform Gram-negative bacilli with tapered ends are seen in the Gram stain as observed in the bottom photomicrograph. The indole reaction is strongly positive and glucose fermentation is variable; other biochemical reactions are negative except for H2S production by some strains. This isolate is commensal in the upper respiratory tract and has been associated with hospital-acquired aspiration pneumonia, lung abscesses, and empyema in hospitalized patients. Based on these observations, select from the multiple choices the name of this isolate.

Fusobacterium nucleatum

Which characteristic is most helpful in separating Leuconostoc species from other streptococcus-like organisms?

Gas from glucose in MRS broth

Which of the following sugars has been fermented when a gram-negative bacillus produces an alkaline slant and an acid butt on triple sugar iron agar (TSI)?

Glucose

The set of tubes in the image to the right are the Hugh and Leifson Oxidative/Fermentative (O/F) basal medium with glucose and a pH indicator of bromthymol blue. This image demonstrates a reaction of:

Glucose non-oxidizer (nonsaccharolytic)

In rapid carbohydrate fermentation testing, Neisseria gonorrhoeae ferments the following sugar(s):

Glucose only

The reactions in the tubes illustrated in this exercise (reading from left to right: TSI, Pseudosel, OF glucose closed, and OF glucose open) indicate that the bacterial species in question is:

Glucose oxidizer

An autopsy of a 1-year-old female admitted to the emergency room 4 hours prior to her death revealed Waterhouse-Friderichsen syndrome. Blood and nasopharyngeal cultures taken prior to her death should reveal an oxidase-positive, Gram-negative diplococcus with the following biochemical reactions:

Glucose positive, Maltose positive, Lactose negative and Sucrose negative

This image is of a Gram stain prepared from a positive blood culture. Which of the following choices is the MOST appropriate report that the tech should provide to the physician?

Gram positive cocci in chains

Which of the following statements reflect accurate identifications of Enterococcus species?

Gram positive cocci in pairs or chains, catalase negative, esculin positive, PYR positive, vancomycin intermediate, motile, yellow pigment: Enterococcus casseliflavus.

Two sputum specimens were submitted to the Microbiology laboratory for culture. A Gram stained smear was evaluated for each specimen prior to culturing. The fields that are shown in these images are representative of the 20 - 30 low power fields (lpf) that were examined. Which one of the two results represents a sputum specimen that is acceptable for culturing?

Gram stain A

All of the following would be suitable for the identification of bacterial antigens, EXCEPT?

Gram stain reactions

A new tech has a presumptive Shigella species via biochemical identification on a stool culture. To confirm, serological testing is performed. The serological testing is negative and the quality control which was run simultaneously passed. What should the tech do next? A new tech has a presumptive Salmonella species via biochemical identification on a stool culture. To confirm, serological testing is performed. The serological testing is negative and the quality control which was run simultaneously passed. What should the tech do next?

Heat a suspension of the organism and then repeat the serological testing

A microbiologist was performing Shigella serotyping on a probable Shigella isolate and the organism did not serotype. The microbiologist was adamant that the organism was a Shigella species because it was lactose negative on Hekton-Enteric agar and non-motile in motility agar. What should the microbiologist do to ensure that false negative testing did not occur?

Heat specimen for 15 minutes and repeat testing

From the multiple choices below, select the most appropriate culture medium for optimum recovery and differentiation of Salmonella and/or Shigella.

Hektoen enteric (HE) agar

The mechanism by which certain strains of Enterococcus species have developed resistance to the synergistic combination of an aminoglycoside and beta-lactam antibiotics is considered:

High level gentamicin resistance

Within the genus Campylobacter, the laboratory test most helpful in selectively identifying Campylobacter jejuni is:

Hippurate hydrolysis

Which one of the following organisms can be isolated from bone marrow specimens?

Histoplasma capsulatum

Mycobacterium tuberculosis can be identified from body fluids in disseminated infections through molecular testing. In fact, antibiotic resistance can be detected in this organism as well by using isothermal amplification. However, this organism must be grown in culture before testing can be performed. All of the following are examples of isothermal amplification methods EXCEPT?

Hybridization

The selective medium XLD is seen in this illustration. What is the significance of the black colonies observable on this plate?

Hydrogen sulfide production

Rocky Mountain spotted fever (RMSF), caused by Rickettsia rickettsii, is MOST reliably diagnosed by which laboratory technique?

IFA testing

A stool specimen can be suspected of harboring Vibrio cholerae if it possesses which of the following characteristics?

If the stool is watery with a high pH and flecks of mucus.

All of the following statements about blood cultures are correct EXCEPT?

If two separate sets (two bottles each set) of blood cultures are requested, draw them both from the same site at the same time.

Using molecular methods to identify organisms can provide GREATER specificity when compared to phenotypic methods. Which of the following organisms would molecular methods not be beneficial over phenotypic methods in identification? A sputum specimen submitted for culture is brick red in color. The organism causing this sputum color also has a distinct polysaccharide capsule and is non-motile. What organism can be associated with this sputum?

Klebsiella spp

Pictured are tiny, gray-white, non-hemolytic colonies growing on blood agar that are non-descript. The Gram stain reveals elongated, rectangular gram-positive bacilli in short chains. Key to the identification would be the lack of biochemical activity. This bacterium is usually recovered as a genital tract commensal, but has also been found to provide protection against other infective bacteria. With these observations, what is the most likely identification of the isolate? Small, smooth, gray-white, 24-hour colonies are seen growing on the surface of sheep blood agar with faint alpha-hemolysis. This isolate is most often part of the normal flora, serving in several body sites as a protection against harmful bacteria through the production of lactic acid. The gram stain reveals long, slender gram-positive bacilli lying singly and in short chains. It is a non-branching, non-spore-former. From the multiple choices, select the presumptive identification of this isolate. From the choices listed below, which organism is classified as an aerotolerant anaerobe?

Lactobacillus spp

An 18-year-old woman woke up in the morning to find that her left knee was hot, swollen, and very painful. She could not walk to work and a friend offered her a ride to the clinic. She had never had a swollen joint before. Physical exam revealed a tender knee joint which yielded purulent synovial fluid on aspiration. Gram-negative intracellular diplococci were seen on the Gram stain. She also had a cervical discharge that was cultured. The cause of her infection would grow best on:

Modified Thayer Martin (MTM) agar at 35º C with CO2

Each of the following tests is helpful in the species identification of Staphylococcus aureus EXCEPT:

Modified dimethyl sulfoxide (DMSO) test

All of the following are reasons why molecular methods for the detection of methicillin-resistant Staphylococcus aureus (MRSA) have gained increasing attention, except:

Molecular methods are are less expensive than cultural methods

Which of the following has been compared to a hockey puck when discussing its morphology on chocolate agar? Which of the following organisms is an aerobic, gram-negative diplococcus that does not ferment sugars and is DNAse positive? The 48-hour growth of small pinpoint gray-white, smooth colonies on chocolate agar (right plate) are most commonly recovered as normal upper respiratory flora but may cause otitis media and sinusitis. There was no growth on Thayer Martin media (left plate). Growth on MacConkey agar is also absent. Short, plump, Gram-negative cocci lying singly and in loose clusters are seen in Gram stain, as illustrated in the lower photomicrograph. This non-fermenter is non-motile, oxidase-positive, and does not utilize carbohydrates (assacharolytic). Nitrates are reduced and DNAse is positive. From these observations, select from the multiple choices the presumptive identification of this isolate. A patient with an upper respiratory infection submits a sputum specimen for culture. A gram stain performed on the sputum specimen reveals gram-negative diplococci. Oxidase testing is positive and carbohydrate degradation tests are inactive. What is the MOST likely identification? A gram-negative, oxidase-positive diplococcus was the predominant isolate from a sputum specimen of a patient with chronic obstructive pulmonary disease (COPD). Based on the reactions seen in the Quad-FERM system shown in the photograph, the most likely identification is: All of the organisms below are known to cause gastroenteritis, EXCEPT: The purulent exudate and the intracellular bacteria (shown by the arrows) as illustrated in this photograph to the right was observed in a direct sputum gram stain of a 70-year-old patient with chronic obstructive pulmonary disease. Which bacterial species most likely grew out in culture?

Moraxella catarrhalis

A culture was taken of a conjunctival exudate. The bacterial species, represented by the tiny colonies seen on this chocolate agar plate were recovered after 48 hours incubation at 35°C. The isolate was cytochrome oxidase positive and highly susceptible to penicillin. What is the most likely identification of this organism?

Moraxella lacunata

The colonies shown in this 5% sheep blood agar (left) and MacConkey agar (right) split frame photograph are most likely those of:

Morganella morganii

A tech is working with a large, spore-forming, Gram-positive bacillus that they believe is Bacillus spp. Which of the following tests could the tech use to ensure this organism is not Bacillus anthracis?

Motility positive

Each of the following characteristics is a prerequisite for a bacterial species to be classified within the family Enterobacteriaceae except:

Motility via peritrichous flagellae

Which of the following media is commonly used when performing the Kirby-Bauer disk diffusion?

Mueller-Hinton agar

Which molecular methodology is used to detect multiple targets in a single sample of CSF when meningitis/encephalitis is suspected?

Multiplex PCR

Which of the following distinguishing characteristic is associated with Streptomyces species?

Musty basement odor

A bacterium was isolated as the cause of a urinary tract infection. The organism showed no lactose fermentation on MacConkey agar (MAC). On triple sugar iron (TSI) media, the organism produced an A/A with H2S. What organism is most likely observed? Prior to receiving antibiotic therapy, a patient had a urinary tract infection with gram-negative, motile rods producing the following reactions: Indole: posH2S (TSI): posMR: posVP: negPhenylalanine deaminase: posUrea: posCitrate: posOrnithine decarboxylase: negGelatin hydrolysis: pos Based on the reactions above, what organism is MOST likely causing the infection

Proteus vulgaris

A member of the Enterobacteriaceae is inoculated into various biochemical media which are shown in the image. Shown from left to right are tiron agar (TSIA), lysine iron agar, urea agar, citrate agar, phenylalanine deaminase agar, and motility indole ornithine agar. This organism is most likely:

Providencia spp.

Select the most appropriate identification of a non-lactose fermenting Enterobacteriaceae based on the following test results: Indole positive TSI K/A H2S negative Citrate positive PDA positive Lysine decarboxylase negative Ornithine decarboxylase negative Urea negative

Providencia stuartii

The following is true of the disk diffusion method of measuring antimicrobial sensitivity:

Provides only an interpretation value of sensitive, intermediate, or resistant correlated to MIC values

The following statements regarding the cell cytotoxicity neutralization assay (CCNA) for Clostridiodes (formerly Clostridium) difficile are correct EXCEPT?

Provides rapid results

On sheep blood agar, Haemophilus influenzae may exhibit satellitism around all of the following bacteria, EXCEPT: A gram-negative rod isolated from a burn patient produced a bluish-green pigment and the following test results: Characteristic fruity odorTriple sugar iron (TSI) agar: Alkaline/alkalineMotility: PositiveOxidase: PositiveOxidative/fermentation (OF) glucose: Oxidative utilization only What is the MOST probable genus of this isolate?

Pseudomonas

Illustrated in this photomicrograph of a gastric biopsy specimen are a few thin, curved and S-shaped bacteria (arrows). This picture is suspicious for Helicobacter pylori. An additional test helpful in confirming this identification is:

Rapid urease

All of the following organisms are known to be resistant to vancomycin EXCEPT?

Rhodococcus equii

Which Pseudomonas species will have yellow colony pigmentation on blood agar?

Pseudomonas fulva

The granular, wrinkled, yellow-pigmented colonies shown in the upper photograph were recovered on chocolate agar after 48 hours of incubation from a respiratory specimen collected from a patient with cystic fibrosis. Note in the lower composite photograph that colonies on the surface of blood agar are flat, granular, and only slightly wrinkled. On MacConkey agar the colonies lack lactose fermentation and lack pyocyanin production. The spot oxidase test is positive, and nitrates are reduced. With these observations, select the presumptive identification of this isolate. Nitrate reduction is the process by which nitrate is reduced to nitrite; in denitrification, nitrate is completely reduced to nitrogen gas. Which of the following species denitrifies nitrate?

Pseudomonas stutzeri

A CSF specimen was sent to the laboratory for analysis. Glucose, protein, and cell count were performed. Based on the following results, what would be the probable cause? AnalyteResultGlucose15 mg/dLProtein150 mg/dLLeukocytes1,000 cells/mm3 neutrophils

Purulent infection

A female was seen by her physician with symptoms of fever, flank pain, frequency, urgency, and dysuria. A urinalysis was performed and had the following results. Which of the following clinical manifestations will this patient have? pH7.6ProteinPositiveBloodPositiveNitritePositiveLeukocyte esterasePositiveBacteriaGram-Negative Rods 4+CastsWhite Cell castRed Cell castCulture100,000 CFU/mL of Escherichia coli

Pyelonephritis

Abiotrophia defectiva (formerly Streptococcus defectivus) and Granulicatella adiacens (formerly S. adjacens, then A. adiacens) are the names currently given to two species of what were previously called nutritionally variant streptococci (NVS). What supplement must be added to the blood culture medium to recover these organisms in cases of "culture-negative endocarditis?"

Pyridoxal

Matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) is used for identification of aerobic bacterial isolates on a urine culture bench. Upon placing the target into the MALDI-TOF instrument, no peaks were found on the quality control wells, but the patient isolates gave good identifications. What caused this issue?

Quality control organism was not added to the target wells

A tech is working on a urine culture and finds the following isolates: Escherichia coli: >100,000 CFU/mL Enterococcus faecalis: 50,000 CFU/mL Klebsiella pneumoniae: 30,000 CFU/mL How should the tech continue with the culture workup?

Quantitate culture and report as mixed urethral flora/contaminants

The test used for the identification of specific capsular serotypes of Streptococcus pneumoniae is:

Quellung

Which one of the following tests should be used to monitor a patient's response to treatment for syphilis:

RPR titer

The OF dextrose activity is a key initial assessment in the presumptive identification of the nonfermentative gram-negative bacilli. Which of the following bacterial species utilizes dextrose oxidatively? (yellow reaction in the open tube)

Ralstonia pickettii (formerly Burkholderia pickettii)

A 62-year-old female undergoing chemotherapy for breast cancer developed fever, abdominal pain, and foul-smelling diarrhea after receiving clindamycin for 5 days. The photomicrograph is an H & E-stained section of colon biopsy revealing focal ulceration and pseudomembranous inflammation. Each of the following laboratory findings will confirm the presumptive diagnosis of Clostridioides difficile-associated colitis EXCEPT:

Recovery of C. difficile in stool

A tech receives a request for VRE colonization testing on a patient in the hospital. Which of the following is an appropriate area of the body for culture for screening?

Rectal area

A tech working in the laboratory receives a call from the floor. The nurse needs to perform a VRE screen on the patient and needs to know what type of specimen to collect. Which of the following is an appropriate specimen for VRE screening? To screen for Vancomycin-Resistant Enterococci, which of the following culture sites is most appropriate?

Rectal swab

Which of the following is a key benefit that molecular methods can offer over culture methods?

Reduced turnaround time

A tech is interpreting a urine culture with a source of suprapubic aspiration. There is one colony of Staphylococcus epidermidis present on the blood agar which was streaked with a 0.01 loop. What should the tech do next?

Report and provide a sensitivity for the S. epidermidis

This Xylose Lysine Decarboxylase (XLD) medium shown in this photograph was isolated from a stool specimen of an immunocompetent adult. Your best action would be to:

Report it as no Salmonella or Shigella isolated

A protected brush specimen was received into the microbiology laboratory from an ICU patient and cultured using a 0.001-mL loop. The culture grew 3 colonies of Pseudomonas aeruginosa. Which of the following is the correct way to report out the organism?

Report out 3,000 CFU/mL of Pseudomonas aeruginosa

On a plate growing Streptococcus pneumoniae, the zone of inhibition around the disk shown in the image has been measured at 23 mm. Based on this result, you should:

Report oxacillin-susceptible

Gram positive cocci isolated from a catheterized urine culture on a 76-year-old male gave the following reactions: Blood agar- creamy, white, opaque colonies with are not hemolytic Catalase- positive Slide coagulase- negative Tube coagulase- negative Novobiocin- susceptible The next action that the medical laboratory professional should take is to:

Report the isolate as coagulase negative staphylococcus

This Gram-positive coccus is catalase positive. The tests shown are a tube coagulase test inoculated with the isolate, and an MRSA screen plate containing 4% NaCl and 6 µg/mL of oxacillin. A 0.5 McFarland standardized inoculum of the isolate is inoculated to the plate. What step should you take next?

Report the isolate as methicillin-resistant Staphylococcus aureus.

An alpha-hemolytic slightly concave isolate from a respiratory specimen gave a zone of inhibition of 18 mm around the optochin disk. What should the next step be?

Report this organism as Streptococcus pneumoniae.

Edwardsiella tarda is known to be associated with which of the following animals?

Reptiles

Gram stain of a spinal fluid revealed pleomorphic, gram-negative rods. Colonies that appeared on chocolate agar after 24 hours of incubation were gray, opaque, and medium in size. A musty odor was noted when the plate was opened. Gram stain of the colonies on chocolate agar showed small, gram-negative coccobacilli. No growth was seen on sheep blood or MacConkey agar. The next step taken by the technologist to identify this isolate would be to show that the organism:

Requires X and V factors

A suspected nocardioform bacterial species was recovered from sputum. The isolate produced mucoid colonies with pink pigment after 4 days on SBA, as shown in the associated image. Staining demonstrated diphtheroid, Gram positive rods with a few branching filaments. It also stained partially acid fast. The most likely identification is: The light pink-yellow, mucoid, non-hemolytic colonies on blood agar, an uncommon isolate, belongs to the aerobic actinomycetes. This species is widely spread among farm animals and may cause human respiratory infections upon animal contact. The Gram stain reveals Gram-positive cocci, with younger colonies also showing branching bacilli, with residuals seen here. Carbohydrates were not utilized (asaccharolytic), and the decarboxylase reactions are also negative. The presumptive identification is:

Rhodococcus equi

Consumption of undercooked poultry or the handling of reptiles could cause which of the following conditions?

Salmonellosis

Which of the following is characterized by hypotension due to systemic infection that does not respond to fluid resuscitation (an attempt to replenish body fluid)?

Septic shock

In the upper bi-plate image are shown colonies growing on MacConkey (left), and on blood agar (right). Relatively large confluent gray-white colonies are observed growing on blood agar, while smaller smooth convex colonies with a deep red pigmentation are growing on MacConkey agar. Note that the pigment is confined to the colonies growing on MacConkey agar that does not diffuse into the adjacent agar. In follow-up to making a presumptive identification, observe that the colonies growing on the DNase agar in the lower image (right) show a positive reaction with clearing of the adjacent agar, compared to the growth of a negative control growing in the streak lines to the left. From these observations, select from the multiple choices the presumptive identification of this isolate.

Serratia marcescens

All of the following Enterobacteriaceae below are appropriately matched with the characteristic listed, EXCEPT:

Serratia marscens - Voges-Proskauer negative

All of the following bacterial species produces a yellow-pigmented colony when growing on 5% sheep blood agar EXCEPT:

Serratia rubidaea

All of the following are true about all members of the Enterobacteriaceae, EXCEPT:

They are all oxidase positive

A sorbitol fermenting organism from a stool specimen is growing on MacConkey with sorbitol agar. The tech decides to double-check for E.coli O157:H7 and serological testing is performed. The serological testing used to identify the somatic antigen (O157) is positive for agglutination. Quality control also passed. What should the tech do next?Set up biochemical or other testing to identify the organism

Set up biochemical or other testing to identify the organism

A patient is showing signs of an intravenous catheter-associated infection. The physician has removed the catheter and sent the catheter tip along with a skin swab of the catheter site to the laboratory for testing. The physician ordered a Gram stain of the skin entry site and a culture of the catheter tip. On which of the following media should the catheter tip be plated?

Sheep Blood Agar and Thioglycollate Broth

Shigella serotyping is performed by using a polyvalent somatic (O) antisera. A Shigella species grew from culture and serotyped as Group C. Which of the following Shigella species serotypes as Group C?

Shigella boydii

Shigella serotyping is performed by using a polyvalent somatic (O) antisera. A Shigella species grew from culture and serotyped as Group A. Which of the following Shigella species serotypes as Group A?

Shigella dysenteriae

A day-care outbreak of diarrhea revealed an oxidase-negative, non-lactose fermenting, nonmotile, gram-negative rod. These characteristics presumptively indicate which organism? All of the following are considered normal flora of the gastrointestinal tract EXCEPT: Although some strains may possess K antigen, which member of Enterobacteriaceae is classified serologically by O antigen because it lacks H antigen?

Shigella spp

A tech is using the H (flagellar) antigen to serotype a suspected Salmonella species. The results of the serotyping are agglutination with one well that indicates a group of possible serotypes, not one particular serotype. Quality control passed. Why did this occur?

Some Salmonella H antigens can occur in multiple strains and serotypes

The photograph illustrates a positive tube coagulase test (Tube A) as compared to the fluid, uncoagulated appearance of the negative control (Tube B). Each of the following Staphylococcus species may produce the reaction seen in Tube A except:

Staphylococcus lugdunensis

Illustrated in the photograph are smooth, non-hemolytic, white 48 hour old colonies incubated at 37oC growing on the surface of blood agar. This isolate was recovered from a urine culture. Microscopic examination of a Gram stain reveals gram-positive cocci. The catalase reaction was positive and the coagulase test was negative. This isolate is a common agent of urinary tract infections. What is the name of this isolate? This is a catalase-positive, coagulase-negative, gram-positive coccus isolated from a urine specimen from a 20-year-old female college student. The image shown is a Mueller Hinton plate streaked with a 0.5 MacFarland standardized inoculum and a 5 microgram disk of novobiocin after overnight incubation. What is the identification of the isolate? All of the following organisms have capsular material as a defense mechanism EXCEPT:

Staphylococcus saprophyticus

The observation of darkly pigmented colonies on agar as illustrated in this photograph is somewhat of a surprise. The colonies of each of the following bacterial species may have an appearance similar to that seen here, EXCEPT: The entire, smooth, golden yellow-pigmented non-hemolytic colonies on the surface of the blood agar plate seen in the upper image have been recovered in hospital acquired infections from patients with cystic fibrosis. A Gram stain prepared from one of the colonies as shown in the lower image, reveal long, narrow gram-negative bacilli arranged singly. Polar flagella would be seen in flagellar stains. All carbohydrate reactions are negative except for the oxidative utilization of glucose and maltose and the organism tested negative for oxidase. Positive biochemical reaction for lysine assists in making a definitive identification. Based on these observations, select the identification of this isolate.

Stenotrophomonas maltophilia

Which of the following urine specimens is a method of collection for uncontaminated urine from the bladder in uncooperative patients or patients unable to void due to physiologic conditions?

Straight Catheterized Urine

A 30-year-old laboratory worker in New York, doing extensive research on laboratory mice, developed sudden onset of fever, chills, headache, and muscle aches. He remembered being bitten by one of the mice about a week previously, although the skin wound healed without incidence. A direct gram stain from the laboratory worker is shown and includes the microorganism causing disease.

Streptobacillus moniliformis

Brucella suis and Salmonella typhi can commonly infect the spleen, liver, and bone marrow. Which of the following reasons allows these two organisms to cause a systemic infection?

They are both ingested by monocytes and/or macrophages within the spleen, liver, and bone marrow

Hippurate hydrolysis is an important characteristic in the definitive laboratory identification of the beta-hemolytic streptococci. The positive ninhydrin reaction, seen in the left tube in the photograph, is produced by: Each of the following bacterial species works synergistically to produce bacterial vaginitis EXCEPT: The entire, smooth, transparent colonies surrounded by distinct zones of beta hemolysis, as illustrated in the photograph to the upper left, were recovered after 24 hours of incubation from a vaginal canal swab culture from a 26-year-old mother with signs of premature labor during her 35th week of gestation. Observed in a Gram stain prepared from one of the colonies were Gram-positive cocci that were arranged in chains of 4 to 15 cells (upper right). More characteristic is the arrow-head zone of beta hemolysis observed in the agar CAMP test shown in the lower right image. From these observations, the presumptive identification of this isolate is most likely? Examine the following test results and identify what action you would take. CAMP: Arrowhead appearance Bacitracin disk: 6mm zone of inhibition PYR: Negative Bile Esculin: Tan appearance, no darkening

Streptococcus agalactiae

The detection of a distinct odor is often helpful in the presumptive identification of bacterial culture isolates. Which bacterial species may produce a distinctive odor of butterscotch or honeysuckle?

Streptococcus anginosus

Illustrated in the top photograph are colonies on blood agar after 48-hour growth at 37° C incubation. The colonies are non-hemolytic, small, entire, smooth, and gray-white. Small Gram-positive cocci arranged in short chains are seen on Gram stain as illustrated in the lower photomicrograph. The key to the identification is the rapid production of esculin and not growing in 6.5% NaCl broth. What is the identification of this organism?

Streptococcus equinus

All of the organisms listed below are matched with the most likely clinical condition found in patients with that organism, EXCEPT:

Streptococcus pneumoniae - cellulitis

The photograph on the right is of a 5% sheep blood agar plate inoculated with a throat culture. It is common practice to stab the agar with the inoculating needle, as seen at the tip of the arrow, in order to detect or accentuate the reaction of:

Streptolysin O

The ability of streptococci to spread within the tissues and cause rapidly advancing cellulitis is due to the production of several virulence factors. Each of the following correctly describes the effects of the specific virulence factor EXCEPT:

Streptolysin S is associated with the rash of scarlet fever and the pathogenesis of the streptococcal toxic shock-like syndrome.

Which bacterial species is most likely represented by the opaque, chalky, white colony appearance as illustrated in the photograph?

Streptomyces anulatus

The colonies growing on Middlebrook agar as shown in the upper left photograph were recovered after 5 days incubation from an aspirate from a superficial skin infection. The gram stain revealed branching bacilli as seen in the lower image. These organisms are acid-fast negative. Illustrated in the upper right photograph are colonies growing on casein medium demonstrating hydrolysis. The MOST likely identification is:

Streptomyces species

A tech is testing a sorbitol negative isolate for possible E.coli O157: H7 from the MacConkey with sorbitol agar plate. The biochemical identification proves the organism is E.coli. Serological testing for the O157 somatic antigen is positive. Serological testing for the H7 flagellar antigen is negative. Quality control for all serological testing passed. What should the tech do next?

Subculture the organism to motility medium for repeat H7 serological testing

A urine specimen, from a premature infant, was sent for culture to the microbiology laboratory and it grew out 30,000 CFU/mL of a coagulase-negative staphylococcus. The physician felt that the growth was skin contamination as the urine was collected in a U-Bag that was attached around the infant's genitalia area. The physician sent a second specimen for culture and it was reported as no growth after 48 hours. Which of the following specimens is the most probable specimen type for the second specimen that was sent to the microbiology laboratory for culture?

Suprapubic Bladder Aspiration Urine

The tech in microbiology receives a call from the outpatient center where the doctor wants to test a patient's wound to determine if is caused by cutaneous anthrax. What should the tech indicate is a proper specimen for collection to detect cutaneous anthrax?

Swab under edge of skin legion

A 6-year-old girl was seen in the emergency department with pain and tenderness in her lower right quadrant. A CBC showed a high white blood cell count with increased segmented neutrophils and bands. The child was admitted to surgery with a diagnosis of appendicitis. During surgery, the appendix appeared normal, but an enlarged node was removed and cultured. A diagnosis of mesenteric lymphadenitis was made. Gram-negative rods were isolated. Which of the following biochemical results are most likely produced by the suspect organism?

TSIA acid over acid, H2S negative, lysine negative, indole variable, urea positive

Beta-lactam antibiotics interfere with cell wall synthesis by all of the following, EXCEPT:

Targeting the 30S ribosomal subunit

Which statement about assays for the antigenic detection of both Clostridioides difficile toxins A and B is TRUE?

The antigenic assays give rapid results.

All of the following statements concerning Rickettsia species are true, EXCEPT:

They are cultured in many hospital laboratories

An expectorated sputum specimen is received for culture at your laboratory. You are preparing to make slides and inoculate the media and are observing the gross appearance of the specimen. The specimen is a mixture of watery, bloody, and purulent material. Which area(s) of the specimen is most likely indicated for culture and slides?

The bloody and purulent areas of the specimen are most indicated for culture and slide preparation.

What is successful molecular identification of methicillin-resistant Staphylococcus aureus (MRSA) based upon?

The detection of the S. aureus genes (orfX, nuc, or coa) gene and the mecA gene.

In this image is a quadrant plate containing brain heart infusion agar supplemented with 6 µg/mL of vancomycin. The right upper quadrant was inoculated with the test strain of Enterococcus faecium. The presence of growth in the inoculated quadrant indicates ___________?

The organism is resistant to vancomycin

The likelihood of colonization and/or infection with Clostridioides difficile is enhanced by all of the following except:

The patient has been previously treated at an orthopedic sports clinic

Two techs performed E.coli O157:H7 serotyping on a suspected colony. The serotyping uses the O157 somatic antigen as the target for agglutination. One tech performed quality control and patient samples by using a suspension of the colony and latex reagent. The results reported by the tech were positive. The second tech also did the serotyping using quality control and patient samples by using a suspension of the colony, latex reagent, and isolate suspension with the negative control. The second tech's results were negative. Quality control passed in all testing. Why did the techs obtain different results for the serotyping?

The second tech tested the suspension with negative control

A urine culture and sensitivity (C&S) specimen is collected at 8 AM at an outpatient clinic and the courier will not be able to pick it up until 2 PM that same day. If refrigeration is not available, how should the specimen be stored until testing is performed?

The specimen should be placed in a container with the proper preservative.

The most likely primary site of infection represented by the Staphylococcus species growing on the surface of this agar plate with a 2 mm zone of inhibition around a 5 µg novobiocin disk is:

The urinary tract

Examine this photo of a 5% sheep blood agar plate from a wound culture workup. All of the following direct tests would be helpful in making an immediate presumptive identification of the organism growing on the plate EXCEPT:

Thermostable endonuclease

Organisms such as coagulase-negative Staphylococcus, Corynebacterium, and alpha streptococcus species are all found on the skin and represent normal skin flora. All of the following are functions of normal skin flora EXCEPT?

They aid in the transmission of nosocomial infections

A 25-year-old female presented in the emergency room with an acute urethral discharge of two days duration. The image to the right shows the Gram-stained smear that was obtained. Many polymorphonuclear leukocytes and intracellular and extracellular gram-negative diplococci were observed. Based on the clinical history and the Gram stain observation, what diagnosis can be made?.

Unable to determine the cause of infection

A patient tested positive for cryptococcal antigen and rheumatoid factor. The results of the cryptococcal antigen should be reported as?

Uninterpretable

A tech is working with a plump, bipolar staining, Gram-negative bacillus that may be Yersinia pestis. Which of the following tests could the tech use to rule out this organism?

Urease positive

Each of the following practices will better ensure the successful recovery of Campylobacter jejuni from stool specimens except:

Use of selenite enrichment broth

Which of the following tests would you employ to examine a CSF for syphilis:

VDRL

A physician suspected that a young, sexually active woman had bacterial vaginosis. Which of the following specimen sources is the correct specimen of choice to support a bacterial vaginosis infection?

Vaginal

Minimum inhibitory concentration (MIC) susceptibility tests should be performed against other beta-lactam antibiotics for Streptococcus pneumoniae isolates from blood cultures and other sterile body fluids. The reason for this is due to an emerging resistance against penicillin and other beta-lactam antibiotics. However, there is one antibiotic that is used to treat drug-resistant Streptococcus pneumonia infections and MIC results should be questioned when a resistant susceptibility is found. Which of the following antibiotics does Streptococcus pneumonia still remain sensitive to? A methicillin-resistant Staphylococcus aureus was recovered from a wound infection. Which antibiotic would be used for treatment?

Vancomycin

The end product of fermentative metabolism of the Escherichia, Salmonella, and Shigella genera is which of the following?

Various mixed acids

Growing on the surface of the anaerobic blood agar plate illustrated in the upper image are indistinct small, gray, convex, translucent colonies free of beta hemolysis. Gram-negative cocci lying singly and in clusters are seen on Gram stain, as illustrated in the lower photomicrograph. Nitrates are reduced, indole is negative, and carbohydrates are not utilized (asaccharolytic). This isolate is part of the microbiota of the mouth, upper respiratory tract, and intestine. What is this organism?

Veillonella parvula

Which of the following organisms is Gram-negative?

Vibrio

The fastidious Gram-negative bacillus featured here has been recovered from individuals in pandemic outbreaks of diarrhea after ingestion of contaminated stream, lake, or well water. In many cases, life-threatening profuse diarrhea resulting in dehydration and electrolyte loss is experienced. Smooth, entire, convex light gray-yellow colonies are observed on blood agar (left upper image). Note the yellow pigmentation of the colonies growing on TCBS agar (Thiosulfate Citrate Bile Sucrose) on the right of the composite image, indicating strong acid production from sucrose. Cytochrome oxidase is also positive. Small, curved, and S-shaped, gram-negative bacilli are seen on the Gram stain. From these observations, select the correct genus/species identification of this isolate. What organism has a toxin that, when released, causes profuse, watery diarrhea? Illustrated in this photograph is the surface of a thiosulfate citrate bile sucrose (TCBS) agar plate which are growing colonies of an unknown bacterial species from a diarrheal stool specimen. The most likely identification is:

Vibrio cholerae

A PYR reaction is shown in the attached image. Which combination of result interpretation and possible organism identification based on the result is correct?

Positive/Enterococcus sp

A clean catch urine specimen was streaked to a sheep blood agar plate and a MacConkey plate with one microliter (0.001 mL) loop. The images to the right demonstrate the observed growth. How would you report the colony count and growth?

10^3 CFU/mL of a gram-negative bacillus

When identifying Mycobacteria by molecular methods, the most reliable gene sequence is:

16S

If a blood agar plate and an EMB plate are both inoculated with 0.001 mL of urine, and 90 colonies of Staphylococcus aureus grew on the blood agar plate, what should be reported?

90,000 colony-forming units/mL of Staphylococcus aureus

When performing quantitative cultures from bronchoalveolar lavage specimens, which of the following colony-forming units per milliliter indicates a true bacterial pneumonia?

>10^4 colony-forming units/mL

The bacterial species growing on the surface of the MacConkey agar plate shown in this photograph, a coccobacillary non-fermenter and a common cause of nosocomial hospital-acquired pneumonia, can be presumptively identified as: Illustrated in the upper composite photograph are non-hemolytic, smooth, entire non-pigmented white colonies growing on blood agar. Human isolates are most commonly from nosocomial infections related to endotracheal tubes and tracheostomies, with peritonitis in patients receiving peritoneal dialysis. Distinctly light lavender-pink pigmented colonies are observed growing on MacConkey agar. Tiny coccobacilli simulating those of Neisseria species are observed in gram stains as illustrated in the lower photomicrograph. Other identifying features include the oxidative production of acids from most carbohydrates (saccharolytic) and a negative oxidase test. From these observations, select from the multiple choices the presumptive identification of this isolate. The positive oxidase reaction as shown in the image (yellow arrow) rules out which of the following "look-alike" bacteria that resemble N. gonorrhoeae? Direct Gram stain from a peritoneal fluid specimen appeared as Gram-positive cocci. After 24 hours, clear, convex, entire colonies grew on blood agar and faint lavender colonies were noted on MacConkey, grown aerobically. Gram stain was repeated and appeared as Gram-negative coccobacilli. The isolate was oxidase negative, catalase positive, non-motile, and resistant to penicillin. What is the presumptive identification?

Acinetobacter baumannii

Aspiration material recovered from a ruptured appendix abscess was inoculated to anaerobic culture media per laboratory protocol. Gray colonies (> 1 mm) grew anaerobically in 24 hours on BBE agar, blackening the media. The photograph illustrates the gram stain features of the organism. The bacterial species most likely associated with the abscess is: All of the following organisms are aerobic organisms, EXCEPT? Cultures from a post-abdominal cellulitis specimen grew Gram-negative pleomorphic rods with the following characteristics: Grows on KV agar but does not show fluorescenceProduces black colonies BBE agarResistant to penicillin Which of the following is the MOST likely identification? An abdominal wound culture grows E. coli on the aerobic culture. The anaerobic culture has the growth of two, gram-negative rods, one of which is aerobic. The other gram-negative rod has 2+ growth on the BBE plate and is resistant to kanamycin, colistin, and vancomycin disc. What is this organism's identification? Which one of the following pathogenic anaerobic bacteria is MOST frequently isolated in clinical laboratories?

Bacteroides fragilis

The tech in microbiology receives a call from the ER where the doctor suspects a patient has inhalation anthrax. What should the tech indicate is a proper specimen for collection to detect inhalation anthrax?

Blood

Illustrated in this photograph is a positive slide coagulase test (Image B) compared to a negative control (Image A). The clumping of the bacterial cells, as seen in Image B, results from the bacterial production of:

Bound coagulase

All of the following are commercial methodologies that Chlamydia and Neisseria identification have been based on, EXCEPT?

Branched chain DNA technology

Which Brucella species has positive H2S production and may or may not need CO2 for growth?

Brucella abortus

What is the medium of choice for isolating Gardnerella vaginalis?

Human blood bilayer Tween (HBT) agar

The following is a non-fermenting, oxidase positive, motile, opportunistic pathogen that most commonly causes respiratory infections associated with chronic granulomatous disease and cystic fibrosis. On sheep blood agar, the organism is described as being small, entire, gray-yellow colonies. On MacConkey, it may appear light pink as shown in the photograph. Identification tests that assist in the identification include Alk/Non-reactive on TSI, lysine decarboxylase positive, oxidation of glucose, lactose, and xylose. It also does not produce gas from nitrate reduction. Which of the following organisms matches the description? Bacteria may be the agents of infections in plants as well as in animals. This organism is the agent of onion bulb rot in plants, but is also an important agent of hospital-acquired infections in humans. Of the Gram-negative bacilli listed below, which is motile with polar tufts of flagella and can produce yellow pigment?

Burkholderia cepacia

An occupation or avocation that should be avoided to prevent infection with Francisella tularensis is:

Hunting and skinning small game

Which of the following is a selective media recommended for the isolation of Clostridioides difficile?

Cefoxitin-cycloserine-fructose agar (CCFA)

All of the following are common causes of infective endocarditis, EXCEPT? Illustrated in the upper photograph are tiny, gray-white, non-hemolytic colonies growing on the surface of blood agar. Recovery is most often from infections in immune-suppressed hospitalized patients. The Gram stain shows Gram-positive bacilli arranged in a "diphtheroid" pattern. Characteristic for making a species identification of this isolate are negative reactions for all enzymes. From these observations, select the presumptive identification of this isolate.

Corynebacterium jeikeium

Enterobacter cloacae colonies were isolated from a blood culture taken from a 45-year-old woman undergoing chemotherapy for breast cancer. Observe this Kirby-Bauer susceptibility plate and the result report form for this organism. From the multiple choices, identify the resistance mechanism (if any) that this organism demonstrates.

ESBL- Extended-Spectrum Beta-Lactamase with Amp C expression

Illustrated in the photograph to the right is the growth of bacterial colonies on blood and MacConkey agars. The media on the bottom left with the red pigmentation on MacConkey agar indicates lactose fermentation. Note the colonies on the sorbitol MacConkey agar plate on the right, which are growing non-pigmented, gray-white colonies. The isolate presented in this exercise is representative of the bacterial species that have been recovered from stool specimens in several outbreaks of patients with diarrhea following ingestion of contaminated ground beef. Which of the following is the identification of this isolate?

Enterohemorhragic E.coli (EHEC)

The organism pictured below was a Gram-positive rod isolated from a sore on the hand of a fish market employee. It is shown on triple sugar iron agar. The organism is also catalase-negative and non-spore-forming. The most likely identification is: Although it is actually non-motile, which Gram-positive, catalase-negative organism produces "bottle brush" growth from the stab inoculation in a gelatin agar tube at 22° C, along with hydrogen sulfide production in TSI agar? Which of the following organisms shows a characteristic "test-tube brush-like" pattern at 22 degrees Celsius?

Erysipelothrix rhusiopathiae

Which of the following instruments is used for continuous monitoring of mycobacterial growth?

MGIT 960

The presence of Gram-negative intracellular diplococci in a genital specimen from a male is diagnostic of which disease?

Gonorrhea

Asaccharolytic use of glucose would be indicated by which of the following reactions in OF glucose tubes?

Green in both tubes with a little blue at the top of the open tube

Which of the following species of bacteria is positive for rapid urease production, as demonstrated by a color change in urea agar from yellow to pink within two hours? The organism seen in the image is found in the stomach mucosa and presumptive identification is often obtained from a positive urease test. Select the organism below. Illustrated in this photograph is an H & E-stained section of a gastric biopsy obtained from a patient with suspected peptic ulcer disease. Based on the biopsy findings, the bacterial species that would most likely be recovered is: A culture was performed on a stool sample. After growth was obtained on the blood agar plate, the gram stain showed curved gram-negative rods. The oxidase, catalase, and urease were positive. What is the most likely bacterial identification?

Helicobacter pylori

The following test may be performed on all swarming Proteus species to differentiate between Proteus mirabilis and Proteus vulgaris: If bacteria produce the enzyme tryptophanase to break down the amino acid tryptophan, which of the following tests will be positive with Kovac's reagent?

Indole

Which of the following organisms has been isolated from nasal secretions and causes atrophic rhinitis, a tissue-destructive disorder in the nose?

Klebsiella pneumoniae subsp. ozaenae

This Gram stain was prepared from a lower respiratory tract specimen. How should this Gram stain be reported?

Many gram-positive cocci in pairs, many polymorphonuclear white blood cells (PMNs)

A patient came into the emergency department with symptoms of meningitis. The patient was suspected of having a blocked cerebral shunt, which can cause meningitis. The shunt was drained and sent to the microbiology laboratory for culture. All of the following organisms are associated with shunt infections EXCEPT? An organism grew out of a spinal shunt. The protocol for the growth of this organism is to notify infection control and the public health department. In addition, any healthcare worker who came in contact with the patient must be treated promptly with antibiotic prophylaxis. Which of the following organisms requires this type of protocol? The bacterial species shown in this composite photograph of a chocolate agar plate and accompanying gram stain, recovered from an autopsy blood culture of a patient dying with Waterhouse Friderichsen syndrome is most likely: An 18-year-old student was seen in the college health center with a sudden onset of headache, fever, and stiff neck. A gram stain of the cerebral spinal fluid sediment is shown in the photograph to the right. The MOST likely cause of this patient's acute meningitis is: The identification of Neisseria species is most often confirmed by observing the specific carbohydrate utilization profile (glucose/dextrose; maltose; lactose; sucrose; yellow is a positive reaction). Based on the carbohydrate reactions as observed in the image, identify the organism:

Neisseria meningitidis

Some strains of Group F Strep can carry the group A antigen, potentially leading to a false positive identification of group A, Streptococcus pyogenes. A spot test that is helpful in differentiating these two species and thus preventing a false report is:

Pyrrolidonyl-b-naphthylamide (PYR)

Smooth gray-white, convex, glistening non-hemolytic colonies were observed growing on the surface of anaerobic blood agar after 48 hours. This isolate was obtained from a nasal swab specimen. Short Gram positive bacilli in short chains and in diphtheroidal-like clusters were observed on Gram stain. Spot test results included a positive catalase and a negative indole reaction. This organism was presumptively identified as Cutibacterium (Propionibacterium) acnes. With this presumptive identification, select from the multiple choices what the next step should be.

Report with added comment: "probable contaminant"

Purulent material is obtained from a carbuncle and submitted for bacterial culture. Many Gram-positive cocci and white blood cells were seen on a direct smear (top right image). Colonies on blood agar are, smooth and gold/yellow surrounded by a narrow zone of beta hemolysis (top left image). Coagulase tests are shown in the bottom images. The slide coagulase test is negative, but the tube coagulase test is positive. The probable presumptive identification is: An infective agent of skin wound infections and an agent of toxic shock syndrome, the large, entire, golden-yellow, smooth convex colonies on blood agar were recovered from a swab specimen after 48 hours incubation at 37o C. In the image to the right, clusters of gram-positive cocci were observed microscopically in a gram stain prepared from one of the colonies. The coagulase reaction was positive. With these observations, select the name of this isolate from the choices given. Which of the following gastrointestinal pathogens has an incubation period of 1-8 hours? Which of the following organisms is both a transient colonizer of skin, as well as the most common cause of bacterial skin infections? An infective agent of skin wound infections and an agent of toxic shock syndrome, the large, entire, golden-yellow, smooth convex colonies on blood agar were recovered from a swab specimen after 48 hours incubation at 37° C. In the photomicrograph, clusters of Gram-positive cocci were observed microscopically in a Gram stain prepared from one of the colonies. The coagulase reactions are pictured in the lower images. With these observations, select the name of this isolate. Which of the following organisms will give a positive coagulase test? Which of the following Staphylococcus species will produce yellow colonies on mannitol salt agar?

Staphylococcus aureus

A catalase-negative, a-hemolytic, gram-positive diplococci was isolated from a sputum specimen. The image shown here demonstrates a zone of growth inhibition around the "P disk," indicating optochin susceptibility. What is the identification of this isolate? A 67-year-old man was seen in the emergency room complaining of cough, fever, and piercing right posterior chest pain. X-ray of the chest revealed consolidation of the right middle lobe of the lung. Sputum culture grew the bacterial species shown in the upper photograph. The lower photomicrograph illustrates a gram-stain of the sputum specimen. The most likely cause of the pneumonia is: The microscopic image shown here is a direct Gram stain of sputum obtained from a 70-year-old man complaining of cough, sputum production, and chest pain. This organism was alpha-hemolytic on blood agar, catalase-negative, optochin ("P disk") susceptible, and bile soluble. What is the identity of this organism? With the widespread use of the pneumococcal vaccine, there has been a decline in the incidence of community-acquired pneumonia by which of the following organisms? The optochin (ethylhydrocupreine hydrochloride) disk is most often used for the identification of which organism? The most frequent cause of bacterial meningitis in adults and in children is: While many isolates of this organism remain susceptible to penicillin, resistance is increasing in some areas due to the organism's altered penicillin-binding proteins. In such cases, the recommended treatment is erythromycin or chloramphenicol. Which of the following organisms does this describe? The microscopic view of a Gram-stained sputum specimen reveals lancet-shaped, Gram-positive diplococci. What presumptive identification may be made? Which of the following organisms typically produces umbilicate (depressed center, concave) colonies? A patient was admitted to the hospital recently with an obvious infection. A sputum specimen was submitted and the microbiologist inoculated it to sheep's blood agar. Based on the colony morphology and the alpha hemolysis seen in the image to the right, the most likely identification is: Small, gray, alpha hemolytic colonies with indented centers were isolated on sheep blood agar from a peritoneal fluid. The following biochemicals were performed: Gram Stain: Gram positive lancet-shaped cocci in chains and pairs Catalase: Negative Optochin susceptibility: Sensitive >14 mmIdentify the organism from the choices provided. This isolate is a catalase negative, gram positive coccus on sheep blood agar. The P disk has 5µg of optochin and the zone around it is 16 mm. It has been streaked perpendicular to a beta-lysin producting strain of Staphylococcus aureus. The presumptive identification is: The organism in the attached photos was isolated from a sputum specimen. The blood agar plates were incubated at 37° C. The upper photo shows 24 hour incubation and the lower photo shows 48 hour incubation. The Gram stain showed lancet-shaped Gram positive cocci in pairs. What is the most likely identification of this organism? Presumptive identification of a bacterial species can often be made by observing the type of hemolysis when grown on 5% sheep blood agar. Which of the following organisms is nearly always alpha-hemolytic? Which of the following organisms is the leading cause of bacterial meningitis in infants, young children, and adults in the United States?

Streptococcus pneumoniae

Illustrated in the top photograph are alpha-hemolytic, entire, gray-white convex colonies that are of a bacterial species that was found to be susceptible to vancomycin. In the lower photomicrograph, gram-positive cocci arranged in chains and in loose clusters that are not species distinctive are seen. Select the bacterial species that are uncommonly vancomycin-resistant.

Streptococcus species

A tech receives a call from the floor regarding antimicrobial therapy. The patient culture yielded an aerobic Gram-negative bacillus and the physician would like to use an antibiotic that inhibits protein translation. Which of the following antibiotics would be the best choice?

Tetracyclin

The diffuse erythroderma and edema of the hand shown in the upper photograph is of a 24-year-old female with fever, headache, and hypotension. The blood agar plate shown in the lower photograph was inoculated with purulent material aspirated from a vertebral disk abscess. The most likely condition is:

Toxic shock syndrome

A tech is working with a small, Gram-negative coccobacillus that may be Brucella spp. Which of the following tests could the tech use to rule out this organism?

Urease negative

Isolation and detection of Gardnerella vaginalis from vaginal secretions is improved by which of the following?

Utilization of human blood agar

The gram-negative bacillus illustrated in the lower photomicrograph was recovered from a skin wound incurred while the patient was swimming in seawater around the Western U.S. coast of the Gulf of Mexico. Note that the gray-yellow colonies grow well on blood agar (upper composite image to the left), but the colonies on TCBS agar (Thiosulfate Citrate Bile Sucrose - composite image to the right) are pale green, indicating the lack of sucrose utilization. The short, slightly curved gram-negative bacilli seen in a gram stain (lower photomicrograph) are consistent with Vibrio species, but not species-specific. Select the presumptive identification of this isolate. Infections with this organism typically either present as primary septicemia or wound infections. Septicemia likely occurs after the organism is ingested while consuming shellfish. Wound infections are associated with some type of aquatic exposure. What organism does this describe? Which of the following microorganisms is associated with foodborne illness contracted from oysters and clams?

Vibrio vulnificus

The urease reaction seen in the Christensen's urea agar slant on the far right indicates:

Weak activity

A 49-year-old farmer developed swelling of the neck beneath the left jaw with enlargement of the left posterior cervical lymph nodes. The photograph to the right is representative of a direct gram stain prepared from purulent material aspirated from one of the enlarged lymph nodes. The organism was not acid fast. What is the MOST likely identification? The growth on a blood agar plate as illustrated in the photograph was prepared from the surface drainage of a subcutaneous abscess of a 50-year-old man following a deep penetrating splinter wound. The colonies on this young culture are small, rough, gray-white, and non-hemolytic. Older larger colonies became sunken centrally having a "molar tooth" appearance. The Gram stain reveals gram-positive branching filaments. Key biochemical reactions include hydrolysis of Esculin, nitrate reduction, and negative catalase. From these observations, select from the multiple choices the identification of this isolate: Gas-liquid chromatography is useful in the identification of anaerobes in addition to Gram-stain morphology. Which anaerobe produces succinic acid in abundance?

Actinomyces israelii

Which of the following organisms is most likely to be associated with gas gangrene: The anaerobe growing on the surface of the blood agar plate, the toxins of which cause a form of necrotizing enteritis known as Darmbrand ("fire bowels") in Germany or "Pig bel" in New Guinea, is: Which of the following organisms is responsible for myonecrosis with gas gangrene, food poisoning as well as necrotizing enteritis, a life threatening that causes ischemic necrosis of the jejunum? A sample from a wound infection, suspected case of gas gangrene, was cultured and showed anaerobic colonies that are small, smooth, light gray-yellow, and surrounded by a distinctive double zone of beta hemolysis (arrows). Gram stain, as illustrated in the lower photomicrograph, are large, non-spore forming, "box-car" shaped gram-positive bacilli. What is this organism that is also related to outbreaks of food-borne diarrhea following ingestion of contaminated meat products? The following organism is an anaerobic organism that produces spores and a double-zone of beta-hemolysis. A 25-year-old motorcyclist incurred superficial and deep penetrating lacerations of his right shoulder when thrown off his speeding vehicle into the ditch. The shoulder became painful and continued to swell over the next 24 hours. The bacterial species shown in the upper image was recovered after 36 hours under anaerobic incubation and the lower image illustrates the microscopic features. What is the most likely identification? A Gram stain of drainage from an open wound revealed gram-positive bacilli with spores. This description would commonly rule out which one of the following organisms? (Choose the BEST response.)

Clostridium perfringens

Which of the following organisms is the most common cause of acute cystitis? The tubes shown in this photograph reading from left to right are Kligler Iron Agar (KIA), tryptophane broth for detecting indole and Simmon's citrate. The KIA tube shows an entirely yellow slant and butt, the indole tube shows a layer of red color, and the Simmon's citrate tube is green in color. Of the bacterial species listed, the one most likely to produce the reactions observed is: Which of the following microorganisms is LEAST likely to produce a capsule or slime layer? A patient has a urinalysis performed and results are: Leukocyte esterase: Positive Nitrate: Positive What organism would the tech expect to find on the urine culture plates Observed growing on the surface of a blood and MacConkey agar bi-plate shown in the upper photograph are large, smooth, entire colonies after 24 hours incubation. The colonies growing on blood agar are yellowish-white; those on MacConkey agar are pink with precipitation of bile salts extending into the agar, better seen in the lower image. A positive acid/acid reaction with gas on Kligler Iron Agar (not shown) and the detection of indole identify this isolate as: A patient with hydrocephalus had a shunt placed 3 weeks ago and is now experiencing symptoms consistent with a CSF shunt infection. When a CSF sample is sent to the microbiology department, the image on the right is observed on the Gram stain. What is the most likely cause of this CSF shunt infection?

Escherichia coli

A culture from a sputum specimen grew a mucoid, lactose fermenting organism. Biochemical testing on this isolate gave the following key reactions: VP: positive; Indole: negative; Urea: 1+, Motility: nonmotile, Citrate: positive. What is the most likely organism given the site of isolation and biochemical reactions? This member of the Enterobacteriaceae gave these reactions: BiochemicalReactionH2S (TSI)NegativeOrnithineNegativeLysinePositiveCitratePositiveUreaPositivePhenylalanineNegativeMotilityNegative What is this organism? The distinctly large, spreading, mucoid colonies seen on blood agar in the upper left image, and the display of lactose fermentation on MacConkey agar in the upper right image provide for a presumptive organism identification. This species is most commonly recovered from respiratory specimens of patients with pneumonia. Observing the absence of motility, a weak reaction for urea, and strong reactions for citrate and Voges-Proskauer confirm the presumptive identification. From the multiple choices, select the name of the isolate presented here. An 87-year old patient had a foot wound that grew gram-negative rods on McConkey agar as pink to dark pink oxidase-negative colonies along with the following results: TSI: A/AIndole: neg.MR: neg.VP: pos.Citrate: pos.H2S: neg.Urea: pos.Motility: neg.Ornithine: neg.Antibiotic susceptibility: Carboxicillin and ampicillin-resistant, all others sensitive. What is the MOST likely organism? What is the probable identity of an organism isolated from a wound culture that demonstrates the following test results? Phenylalanine Deaminase = negative TSI = A/A gas Citrate = positive Lysine = positive SIM = negative/negative/negative Urea = weakly positive The reactions in a portion of the API strip, shown in the photograph, most closely identifies which organism? The top image shows a MacConkey agar plate on which mucoid, lactose fermenting colonies are present. The bottom image is the bacterial isolate streaked on the surface of a Mueller-Hinton agar plate. The disk to the left is ceftazidime, and the disk to the right is a combination of ceftazidime + clavulanic acid. Note the larger zone of inhibition around the combination disk on the right, an indicator for extended-spectrum beta-lactamase (ESBL) activity. Which of the following organisms fits this situation? From the choices listed below, choose the most likely associated bacterial species represented in the image as pink, runny, mucoid colonies at 48 hours incubation on MacConkey (MAC).

Klebsiella pneumoniae

Illustrated in the upper photograph to the right are small, gray-white to light yellow colonies surrounded by zones of beta hemolysis. Short, gram-positive bacilli with rounded ends that lie singly or in loose clusters are observed in gram stains. Two key identifying features, as illustrated in the lower photograph, are a narrow band of "umbrella" motility observed beneath the surface of semi-solid motility medium and the deep black slant of positive esculin activity. This species may be recovered during influenza-like infections during the 2nd and 3rd trimesters of pregnancy. With these observations, which of the following organisms is the identification of this isolate? An organism isolated from the spinal fluid of a newborn produced small, grayish, slightly translucent beta-hemolytic colonies on sheep blood agar. A Gram stain of the colony showed small Gram-positive rods that look like diphtheroids. The organism is MOST likely: Which organism matches the reactions shown? Left tube: Motility agar (note subsurface flare shown by arrows) Middle tube: Esculin hydrolysis (+) Right tube: Voges-Proskauer(VP) (+) A gram-positive bacillus grew as a diffusely beta-hemolytic colony from a newborn. It was catalase-positive and had tumbling motility on a hanging drop preparation. The image shows how the organism grew in the motility medium. What is the most likely diagnosis? Observed in the top photographs are colonies growing on blood agar after 24 hours incubation, obtained from a positive blood culture. The colonies are tiny and surrounded by narrow zones of beta hemolysis. The initial presumptive identification was that of a Streptococcus and a CAMP test was set up. A follow-up Gram stain (middle image) revealed Gram-positive bacilli in loose clusters rather than cocci. The lower image demonstrates a rectangular zone of hemolysis in the CAMP test, compared to the arrow-head shape of a control Streptococcus. From these observations, select the most likely presumptive identification of this isolate. Which bacterial species is a common agent of neonatal bacteremia? Of the organisms listed, which is most likely to be contracted following consumption of unpasteurized milk? The red arrow in the photograph is pointing to a typical arrowhead-shaped zone of hemolysis that is produced by Streptococcus agalactiae with the CAMP test. A beta-hemolytic Gram-positive bacillus that produces a rectangular-shaped area of hemolysis as shown by the blue arrow is: A 30-year-old Hispanic pregnant female developed fever and signs and symptoms of meningitis following ingestion of cheese sent by relatives in Mexico. The colonies recovered from a positive blood culture are shown in the upper photograph; the microscopic features are in the lower photograph. The most likely identification is:

Listeria monocytogenes

A wound specimen was received into the laboratory and a large Gram-positive rod was isolated. The microbiologist suspected the isolate was a probable Bacillus anthracis and had to rule in/out before reporting. All of the following tests must be performed before calling the species Bacillus anthracis EXCEPT?

Oxidase

Acinetobacter spp. are similar to Neisseria spp., EXCEPT Acinetobacter spp. are generally: A tech is working with a small Gram-negative coccobacillus that may be Burkholderia pseudomallei. Which of the following tests could the tech use to rule out this organism? All of the following are characteristics of Brucella are EXCEPT:

Oxidase negative

Which of the following is a rapid latex agglutination method for detecting Methicillin-Resistant Staphylococcus aureus (MRSA)? Oxacillin resistance of MRSA is due to the production of which of the following penicillin-binding proteins (PBPs)?

PBP2a

All of the following statements about peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH) are true for Staphylococcus EXCEPT?

PNA-FISH assays provide differentiation between Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureus (MSSA).

The cytochrome oxidase-positive bacterial species that is DNAse negative, ornithine decarboxylase positive, and is associated with gastroenteritis in children after the ingestion of contaminated water is most likely: Which of the following species is an oxidase-positive, glucose-fermenting, Gram-negative bacilli?

Plesiomonas shigelloides

Observation of colonies producing brick red fluorescence under long-wave ultraviolet light on KVLB agar allows for presumptive identification of which anaerobic bacterial genus? The saccharolytic anaerobe that produces red fluorescing colonies when illuminated with a Wood's lamp, as shown in this photograph, is:

Prevotella

The bacteria producing the swarming on the surface of the 5% sheep blood agar plate shown in the photograph was indole negative. The most likely identification is: The reactions observed in this Kligler Iron Agar slant (left) and Christensen's urease slant (right) provide the presumptive identification of: Shown in this photograph is a Kligler Iron Agar (KIA) slant (left) and a Christensen's urea agar slant (right) after inoculation with an unknown bacterial species and incubation for 24 hours at 35oC. The reactions shown permit a presumptive identification of: Shown here is a Kligler Iron Agar (KIA) tube with black pigmentation is confined to the butt of the tube. From the multiple choices, select the bacterial species that produces the reaction seen in the lower image of the KIA tube. The attached photograph shows a Christiansen's Urea slant four hours after it was inoculated with a Gram-negative rod. Which of the following organisms is the most likely?

Proteus mirabilis

The tubes shown in the image are O/F basal medium with glucose and a pH indicator of bromthymol blue. As shown, the tube on the left has a large layer of mineral oil on top of the medium (closed), while the tube on the right does not have a mineral oil overlay (open). The image below demonstrates a typical reaction for which organism? What bacterial species is rarely part of the normal microbiota of healthy humans? Each of the following organisms may possess extended-spectrum beta-lactamase (ESBL) activity except: A 22-year-old construction worker incurred 3rd-degree burns to the chest and arms when a boiler he was installing blew up. On the 5th hospital day, the weeping wounds became infected, exuding what was described as green pus. The image illustrates the Gram stain prepared on a direct smear of the exudate. What is the MOST likely bacterial cause of the infection? The bacterial species, a typical colony of which is illustrated in this photograph, and a common bacterial cause of otitis externa, also known as "swimmer's ear", can be identified as: The detection of a distinct odor is often helpful in the presumptive identification of bacterial culture isolates. Which bacterial species produces a distinctive odor of grapes? Which of the following is oxidase-positive? Which of the following is a nonfermenter? Which Pseudomonas species produces pyocyanin (bright bluish pigment on Mueller-Hinton agar)? The organism growing on Blood Agar and MacConkey Agar in the attached photograph was recovered from the burn wound of a patient. The Gram stain is also attached. This organism is a non-fermenter and can grow at increased temperatures (42 °C). Upon additional testing, the organism was positive for pyocyanin production. Which of the following is the most likely presumptive identification of this organism? Exudate from a burn submitted on a swab for bacterial culture grew a gram-negative bacillus that was oxidase-positive, produced an alkaline slant and butt on TSIA, was resistant to numerous antibiotics, and produced a green, water-soluble pigment. This organism would be identified as: The colonies shown in the blood (BAP) agar (upper) and MacConkey (MAC) agar (lower) biplate are a 24 hour growth from an aerobic blood culture bottle that became positive at 12 hours after inoculation. The appearance of the colonies on MAC agar rules out the following bacterial species:

Pseudomonas aeruginosa

Which of the following Enterobacteriaceae produces H2S? A blood culture yielded an organism with the following reactions: TSIA: K/A, gas (+), H2S (+) Citrate: Positive Indole: Negative Lysine: Positive Ornithine: Positive Motility: Positive Phenylalanine: Negative ONPG: Negative Urease: Negative What is the most likely identification of this organism The select reactions observed in the partial API strip illustrated in this photograph, reading from left to right, are: ONPG negative; arginine, lysine, and ornithine decarboxylases positive; citrate positive; H2S positive, and the remaining reactions negative. These reactions are most consistent with which bacterial genus? Which Enterobacteriaceae are non-lactose fermenters on MacConkey (MAC) agar, have green colonies with black centers on Hektoen enteric (HE) agar, and on xylose-lysine-deoxycholate (XLD) agar will have red colonies with black centers?

Salmonella spp

Illustrated in this photograph are the biochemical reactions of an unknown bacterial species produced in Kligler Iron Agar, Sulfide Indole Motility agar, indole broth, Voges Proskauer broth, and Simmons citrate. The bacterial species most likely producing the reactions seen here is: History records an outbreak with the sudden onset of high fever, headache, and abdominal pain among 93 persons who had attended a public church dinner the week before. The photograph of an XLD agar plate is representative of the organism that may have been recovered from blood cultures from any one of these 93 persons. The most likely identification is: Serological detection of the Vi antigen aids in the identification of: On MacConkey (MAC) agar, an isolate from a stool sample produced clear, colorless colonies. On Hektoen enteric (HE) agar, colonies were green with black centers, indicative of H2S production. Additional biochemical tests were positive for methyl red and negative for indole, VP, citrate, and PAD. From the choices listed, which species best matches the characteristics described? Examine the KIA tube on the right in the image provided and determine which of the following organisms produces the biochemical reaction seen.

Salmonella typhi

A Staphylococcus species recovered from a CSF shunt culture was found to produce acid from sucrose and maltose and showed alkaline phosphatase activity. The staphylococcus was also coagulase-negative. The most likely identification is: A body fluid was sent to the microbiology laboratory for culture and after 48 hours of non-CO2 incubation, a small catalase-positive, coagulase-negative, Gram-positive cocci in clusters grew on sheep blood agar. This organism was considered to be a possible contaminant since this organism is part of the normal skin microbiota. Which of the following organisms grew in the body fluid? Each of the bacterial species listed below may be associated with culture-negative endocarditis EXCEPT: Out of the given choices below, which one of the following bacteria is the MOST frequent cause of prosthetic heart valve infections occurring after heart surgery? Observed on the surface of blood agar are smooth, white, 48-hour-old colonies incubated at 37oC, demonstrating a positive catalase reaction and a negative coagulase reaction. The sample was taken from an intravenous catheter. In the photomicrograph are gram-positive cocci distinctly arranged in loose clusters and in tetrad formation. From these observations, select the presumptive identification of this isolate. A left arm abscess collected from an 8-year-old male patient grew small white colonies on 5% sheep blood agar after 24 hours incubation at 35°C in 5-10% CO2. The Gram stain of the organism showed small tightly grouped Gram-positive cocci. Which of the following organisms is the most likely identification? Which of the following is the most common etiologic agent identified in prosthetic valve endocarditis?

Staphylococcus epidermidis

A patient presents with cellulitis and culture growth small beta hemolytic colonies on 5% Sheep blood agar. The gram stain of the organism is included. What is the most likely cause of the infection? This image shows a gram-positive, catalase-negative coccus on sheep blood agar (beta-hemolytic). Please note the reactions with bacitracin (A) and trimethoprim-sulfamethoxazole (SXT) disks seen on the right side of the agar plate. On the left side of the agar, a beta lysin-producing Staphylococcus aureus is streaked perpendicular to the unknown organism. What is the presumptive identification of this organism? Complete hemolysis of sheep blood agar as demonstrated by the image below would be seen in which of the following catalase-negative isolates? Large, gray to white, beta-hemolytic colonies were isolated on sheep blood agar from peritoneal fluid. The following biochemicals were performed: Gram Stain: Gram-positive cocci in chains and pairs Catalase: Negative PYR: Positive Bacitracin Sensitive Identify the organism from the choices provided. The bacterium in the image to the right is also referred to in the quote below, what is the identification of this bacteria? "If a pregnant woman be attacked by erysipelas of the womb, it is fatal." - Hippocrates

Streptococcus pyogenes

Observe the Optochin "P" disc reaction Illustrated in the upper left photograph on the surface of blood agar. Heavy growth of tiny, alpha hemolytic colonies are observed growing on the agar surface that extend to the outer margins of the paper disc. The Gram stain presented in the lower photomicrograph reveals small Gram positive cocci lying singly, in small clusters, and more typically in long chains. This isolate has been recovered from blood cultures in cases of post-valvular endocarditis. Select the presumptive identification of this isolate.

Streptococcus viridans

Which of the following organisms causes disease by direct invasion of tissues? An 8-year-old boy underwent a laparotomy for clinical signs and symptoms of acute appendicitis. Instead, the appendix did not appear inflamed, but the mesenteric lymph nodes were enlarged and edematous. The photomicrograph is a close-in H & E section of an area within one of the lymph nodes, showing hyperplasia and focal necrotizing inflammation. What bacterial species is most likely causing this reaction? This photograph is of an isolate from a stool culture on a 4-year-old child with gastroenteritis. The medium contains cefsulodin, irgasan, novobiocin, bile salts, mannitol, neutral red, and crystal violet. Further identification tests will most likely identify this isolate as: A stool culture from a hospitalized patient produces the following characteristics: Gram-negative bacillusUrease positiveWeakly fermentativeTSI slant is A/A These reactions suggest that the organism is most likely:

Yersinia enterocolitica