Micro medialab exam
What is the purpose of using alcohol-acetone or acetone in the Gram stain procedure?
Decolorizes all Gram-negative organisms
The production of polar germ tubes is a characteristic that is associated with which of these dematiaceous fungi?
Bipolaris species
Which of the culture media listed is selective for the isolation of Yersinia enterocolitica in stool samples?
Cefsulodin-Irgasan-Novobiocin (CIN)
Stool is the specimen of choice for the recovery of which one of the following parasites?
Diphyllobothrium latum
When are data collected in a real-time PCR procedure?
During nucleic acid amplification
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
Which of the following is used to standardize the bacterial inoculum used in a disk diffusion test (Kirby-Bauer method)?
0.5 McFarland standard
Which of the following is the most commonly encountered enterococcal species?
Enterococcus faecalis
All of the following are true about hybridization in PCR procedures, EXCEPT?
Hybridization cannot happen between a strand of DNA and a strand of RNA
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
Which of the following best describes the size and staining characteristics of yeast cells on a Gram stain?
About the same size as red blood cells and stain purplish-blue.
A specimen is suspected to contain which one of the following organisms because it may be cultured by placing it on an agar plate with an overlay growth of Escherichia coli?
Acanthamoeba species
If a mycobacterium sp infectioni suspected on a bone marrow or body fluid, what stain should be used to detect these bacteria?
Acid-fast stain
Pseudomonas aeruginosa is often used as a bacterial species for the quality control of Triple Sugar Iron (TSI) Agar. The expected reaction is:
Alkaline slant/alkaline butt
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.What is the most likely type of pneumonia?
Aspiration pneumonia
Which of the following statements is TRUE concerning handling suspected bioterrorism agents received in a typical clinical laboratory?
At least a class II biological safety cabinet (BSC) should be used.
What biosafety level (BSL) is required by the Centers for Disease Control and Prevention (CDC) for working with Mycobacterium tuberculosis if there is a possibility that aerosols might be released?
BSL-3
A patient presents at the ER with severe diarrhea and dehydration, marked with rice-water stool. The patient has a travel history to India. A stool culture was obtained and grew comma-shaped, gram-negative bacilli. What is the most likely diagnosis for this patient?
Cholera
Which of the following can produce indole?
Chryseobacterium spp.
From the choices listed below, which organism is classified as an obligate anaerobe?
Clostridium novyi
Which of the following organisms produces a double zone of hemolysis on blood agar?
Clostridium perfringens
Which of the following is a common cause of urinary tract infections?
Escherichia coli
Which of the following terms is used to describe the appearance of rod-shaped bacteria?
Filamentous
What is the purpose of the iodine that is used in the Gram stain procedure?
Fixes the crystal violet to the cellular components of gram-positive bacteria.
Which term describes the cellular morphology of bacteria with a pointed end?
Fusiform
Based on the image to the right, the issued gram stain report should read, "Many WBC with..
Gram positive cocci in pairs.
Observation of each of the following characteristics is helpful in differentiating between Nocardia species and Mycobacterium species EXCEPT:
Gram positive staining
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
The biochemical testing results of an alpha-hemolytic streptococcus show that the isolate is bile esculin-positive, but does not grow in the presence of 6.5% NaCl. The MOST PROBABLE identity of this isolate is:
Group D streptococcus, non-enterococcus
The term "HACEK" is often associated with infective endocarditis. All of the following organisms are included in the "HACEK" group, EXCEPT?
Haemophilus influenzae
Each of the following laboratory characteristics can be used to separate Bacteroides fragilis from the closely related Prevotella/Porphyromonas group of anaerobes EXCEPT:
Indole production
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
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
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) (+)
Listeria monocytogenes
The appropriate media for the isolation of anaerobic bacteria from any source would normally include all of the following except:
MacConkey agar
Immunocompromised patients, such as those with Acquired Immunodeficiency Syndrome (AIDS) are at an increased risk of contracting an unusual form of pneumonia from which of the following microorganisms?
Pneumocystis jiroveci (carinii)
What color would the agar be around a colony of Staphylococcus epidermidis growing on mannitol salt agar (MSA)?
Red
ram 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.
Common colds are most often associated with which agent?
Rhinovirus
Which yeast species is most consistent with the colony morphology as seen in the lower right quadrant of this image?
Rhodotorula species
Rocky Mountain spotted fever (RMSF) is transmitted by the bite of a tick infected with:
Rickettsia rickettsii
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?
Salmonella
Important applications of polymerase chain reaction (PCR) include the following with the general exception of:
Search for mutations with large deletions
The ONPG (ortho-nitrophenyl-Beta-D-galactopyranoside) test is used to
Separate late lactose fermenters from lactose-negative bacteria based on the production of beta-galactosidase
All of the following are considered normal flora of the gastrointestinal tract EXCEPT:
Shigella
Which of the following statements is true regarding the Gram-stained smear that is represented by this image?
The smear is underdecolorized and shows precipitated and crystallized stain
Which of the following statements about Gram-positive bacteria is TRUE?
They resist acetone-alcohol decolorization
Which of the following is a characteristic of Francisella tularensis?
Tiny, weak-staining, gram-negative coccobacilli
A woman presents to her physician complaining of a foul-smelling yellow vaginal discharge. The following was reported from the sample of the vaginal secretions: Wet prep: Many WBCs seen, no Clue Cells seen, microorganisms (20µm) seen with jerky motility Vaginal pH: 6.0 Amine (Whiff) Test: Positive What is the most likely cause of this vaginal infection?
Trichomonas vaginalis
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
Which one of the following tests would be positive in the presence of Klebsiella spp.?
Voges-Proskauer test
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
What bacteria is responsible for the bubonic plague?
Yersinia pestis
Different species of neisseria can be differentiated from each other by
carbohydrate utilization
Which of the following is a presumptive test for the identification of Lancefield group A Streptococcus:
Bacitracin susceptibility
The image on the right is a Wright-Giemsa stained CSF smear (1000X). What structures are indicated by the arrows?
Bacteria
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
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:
Cefoxitin
This member of the Enterobacteriacea was isolated from a stool specimine and gave the following biochemical results: 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
The serum medium and methylene blue stain originally described by Loeffler are both helpful in the identification of:
Corynebacterium diphtheriae
All of the following are common causes of infective endocarditis, EXCEPT?
Corynebacterium jeikeium
The India ink preparation is used for presumptive identification of which organism?
Cryptococcus neoformans in CSF
Which one of the following statements about Campylobacter jejuni is false?
It does not require special incubation conditions to grow in culture.
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 characteristics is a prerequisite for a bacterial species to be classified within the family Enterobacteriaceae except:
Motility via peritrichous flagellae
A sputum sample from a patient with a pulmonary abscess is received in the laboratory. After several days of incubation the following findings are noted: Yellow, irregular colonies growing on a blood agar plate (BAP) under aerobic conditions. Acid-fast stain shows that the organisms are partially acid-fast. Which of the following organisms should be suspected?
Nocardia asteroides
Which of the following organisms is a cause of cutaneous infections?
Nocardia brasiliensis
Which of the following tests would be most useful in the identification of Streptococcus pneumoniae?
Optochin
All of the following are characteristics of Brucella are EXCEPT:
Oxidase negative
The following is the BEST test to differentiate between Aeromonas hydrophila and Escherichia coli from a wound culture:
Oxidase production
Which of the following is oxidase-positive?
Pseudomonas aeruginosa
All of the following information should be included in a direct microscopic examination of a Gram-stained culture smear report EXCEPT:
Size of bacteria
Which of the following Staphylococcus species will produce yellow colonies on mannitol salt agar?
Staphylococcus aureus
Which of the following organisms will give a positive coagulase test?
Staphylococcus aureus
Which of the following is the most common etiologic agent identified in prosthetic valve endocarditis?
Staphylococcus epidermidis
The optochin (ethylhydrocupreine hydrochloride) disk is most often used for the identification of which organism?
Streptococcus pneumoniae
