2016.7.Microbiology

A key laboratory characteristic by which Mycobacterium bovis can be separated from Mycobacterium tuberculosis is:

Growth inhibition by thiopine-2-carboxylic acid hydrazide (T2H)

Match the name of each of the bacterial species listed with its most likely gram staining features as illustrated in the photographs.

Staphylococcus epidermidis A Viridans streptococcus B Streptococcus pneumoniae C Enterococcus faecalis D

A 30 year old laboratory worker 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. The gram stain preparation illustrated in the photomicrograph is representative of the organism recovered from blood cultures.

Streptobacillus moniliformis

Which two of the following tests are helpful for documenting previous Streptococcal throat and skin infections:

ASO titer Anti-DNase B

A 36-year old woman is a known intravenous drug abuser, and gives a history of "several previous episodes of hepatitis". The laboratory workup is as follows: HBsAg- Reactive anti-HBs- Negative anti-HBc- Total Positive anti-HBc IgM- Negative anti-HAV- Total Positive anti-HCV- Positive anti-HAV IgM- Negative Which of the following diagnoses can be excluded based on laboratory data and current symptoms and history?

Acute hepatitis A

The colonies growing on the surface of this 5% sheep blood agar plate were recovered from a throat swab of a 19 year old girl with acute pharyngitis. The visual identification was Streptococcus pyogenes. Surprise! Gram stain revealed club-shaped gram positive bacilli with rudimentary branching. Of the bacterial species listed, the most probably identification is:

Arcanobacterium hemolyticum

The presence of hyaline, septate hyphae, and a young conidiophore with a foot cell and a swollen vesicle in a fungus culture are excellent clues indicative of:

Aspergillus

Which animal was involved in the reassortment of influenza A viruses that led to the 2009 novel influenza A H1N1 virus?

Pigs

Which of the following is a confirmatory test for syphilis:

FTA-ABS

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

- Gram-positive cocci in pairs or chains, catalase negative, black colonies on bile esculin agar, growth in 6.5% salt broth: Enterococcus species. - Gram-positive cocci in pairs or chains, catalase negative, esculin positive, PYR positive, vancomycin intermediate, motile, yellow pigment: E. casseliflavus.

Match the name of the Mycobacterium species listed with its most likely associated disease presentation as illustrated in the photographs.

- Mycobacterium avium/intracellulare Upper Left (GI biopsy) - Mycobacterium marinum Upper Right (subcutaneous skin infections) - Mycobacterium tuberculosis Lower Left (upper lobes of lungs) - Mycobacterium scrofulaceum Lower Right (cervical lymph nodes)

Match the differential/ selective enteric medium with its characteristic indicator, fermentable, and bacteriostatic.

- Xylose-lysine-deoxycholate - phenol red, lactose, bile salts - Eosin methylene blue - eosin Y and methylene blue, lactose, eosin Y and methylene blue - Bismuth sulfite - bismuth sulfite, glucose, brilliant green - Salmonella-shigella - neutral red, lactose, bile salts

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

10-14

Match the names of each of the infectious diseases listed with its most likely corresponding bacterial agent.

"Pinkeye" Haemophilus aegyptius "Swimmers ear" Pseudomonas aeruginosa Rat bite fever Streptobacillus moniliformis Melioidosis Burkholderia pseudomallei

Key characteristics by which Klebsiellapneumoniae can be suspected when an unknown member of the Enterobacteriaceae is recovered in primary culture include:

- Absence of motility - Failure to decarboxylate ornithine

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:

B-galactoside permease

Which one of the following organisms is commonly cultured from the nasopharynx of healthy people but is RARELY pathogenic:

Corynebacterium species

Which two of the following organisms are gram positive?

Erysipelothrix Lactococcus

Which of the following organisms causes thrush:

Candida albicans

The ingredient added to culture media to enhance the recovery of the dimorphic fungi by preventing the overgrowth of more rapidly growing, saprophytic molds is:

Cycloheximide

What is the purpose of using alcohol in the gram stain procedure:

Decolorize all gram negative organisms

Look, oh look at the little red dot, Tell me, O tell me, who I am not.

Haemophilus influenzae

My home is in the stomach coat, Urea serves as my anecdote.

Helicobacter pylori

This 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. This is how it appeared on triple sugar iron agar and motility medium. What is the most likely diagnosis?

Listeria monocytogenes

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

M Antigen

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)

Illustrated in this photograph is an agar plate on which an unknown species has been inoculated. A 5ug novobiocin disk, a 100ug furazolidone disk, and a 0.04ug 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

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 Gram stain. She also had a cervical discharge that was cultured. The cause of her infection would grow best on:

Modified Thayer Martin agar at 35ºC with CO2

What is the MOST likely identification of an acid-fast bacillus that demonstrates the following characteristics? slow growth cream to tan colored colonies when grown in the dark development of yellow pigment upon exposure to light

Mycobacterium kansasii

Which of the following is the likely identification of an acid fast bacilli recovered from an induced sputum with these culture findings? slow growth at 37o C niacin test = negative pigmented photochromogenic nitrate test = positive catalase = positive

Mycobacterium kansasii

What is the MOST likely identity of an acid-fast bacilli that showed buff colored, dry, heaped colonies; niacin, nitrate, and urease positive; and took 23 days at 35ºC to grow?

Mycobacterium tuberculosis

Match the names of each of the conditions listed with the name of its most likely associated anaerobic bacterial agent.

Myonecrosis Clostridium perfringens Root canal abscess Prevotella melanogenica Carcinoma of the colon Clostridium septicum Hepatic abscess Fusobacterium necrophorum

Nitrate reduction is the process by which nitrate is reduced to nitrite; in denitrification, nitrate is completely reduced to nitrogen gas. Match the name of each of the bacterial species listed below into the appropriate bucket indicating whether it reduces or denitrifies nitrate.

Nitrate reduction Yersinia enterocolitica Denitrification Pseudomonas aeruginosa Nitrate reduction Citrobacter amelonaticus Denitrification Pseudomonas stutzeri

Illustrated in this photograph are two tubes of lysozyme broth. The bread crumb-like colonies seen in the left tube, indicating resistance to the action of lysozyme, is most consistent with:

Nocardia otitidiscaviarum

The capsular material used to identify capsular subtypes of Pneumococci consists of:

Polysaccharides

An anaerobe was recovered from a blood culture after 92 hours incubation. A gram stain of the isolate is illustrated in the photomicrograph. The most likely identification is:

Propionibacterium acnes

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

Quellung

On a plate growing S. 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

Which of these laboratory methods are recommended for confirmation of influenza A H1N1 subtype infection?

Reverse transcriptase-polymerase chain reaction (RT-PCR)

Public health guidelines recommend that laboratory specimens for influenza testing must be manipulated using which of the following safety precautions?

Safety cabinet

This member of the Enterobacteriaceae is shown on triple sugar iron agar, lysine iron agar, urea agar, citrate agar , phenylanine deaminase agar, and motility indole ornithine agar. It should be identified as:

Salmonella spp.

Nocardia farcinica has been distinguished from other members of the Nocardia asteroides complex because most strains are resistant to erythromycin and other antibiotics commonly used to treat nocardia infections, and are more commonly recovered from patients with severe underlying illness. Characteristics that are helpful in the preliminary identification of this species include:

The ability to grow at 45°C A white opacity around colonies on Middlebrook agar

C. difficile disease is more likely to occur when:

The balance of the gastrointestinal flora is altered by previous antibiotic therapy. The patient has previously been hospitalized. The patient has a chronic health condition.

Humans become infected with sylvatic plague by:

The bites of rat fleas

Why were Chlamydia and Neisseria logical targets for the development of a commercial molecular assay? (Choose all that apply.)

These organisms are of concern for significant patient populations. The organisms are difficult to sustain in transport. The sensitivity of culture and antigen detection methods was not optimal.

Which of the following specimens would not be considered suitable for anaerobic culture:

Throat swab

Match the names of the organisms listed with the appropriate bucket indicating whether each more commonly causes clinical disease via toxin production or via direct invasion.

Toxic infection Clostridium botulinum Toxic infection Vibrio cholerae Invasive infection Yersinia enterocolitica Toxic infection Shigella sonnei

Streptococcus pneumoniae is the most common cause of fatal community-acquired pneumonia.

True

The red ring at the top of the media in this tube indicates a positive indole reaction. The precursor substance in the medium from which the indole is produced is:

Tryptophan

Select the morphologic structure that identifies Candida albicans and distinguishes it from most other Candida species.

chlamydospore

Enterobius vermicularis infection occurs through:

ingesting or inhaling ova

Which of the following is not considered a potentially infectious body fluid for transmitting HIV?

sweat

Gram stains are performed on positive blood culture bottles. Match the organism that MOST closely resembles the description of the Gram stain morphology provided.

- Bacillus anthracis - Large, gram-positive rods with square ends in short chains - Yersinia pestis - Gram-negative rods demonstrating bipolar staining - Francisella tularensis - Very tiny, pale staining, gram-negative coccobacillus; often difficult to see individual cells - Brucella species - Small, gram-negative coccobacilli that appear gram-positive due to retention of crystal violet stain; individual cells present

Match the names of the Corynebacterium species listed with its most likely associated infection or clinical syndrome.

- C. xerosis/striatum complex - Acanthamoeba-associated contact lens keratitis - C. minitissmum- Erythrasma - C. ulcerans - Toxic diphtheria-like pharyngitis - C. pseudotuberculosis - Suppurative granulomatous lymphadenitis

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 in 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")

The production of polar germ tubes is a characteristic that is associated with which of these dematiaceous fungi?

Bipolaris species

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 Oxidase: negative Motility: negative The MOST probable identification of this isolate is:

Bordetella parapertussis

Surprise! Animals are not the only creatures infected with bacteria. The bacterial species causing onion rot is:

Burkholderia cepacia

Which one of the following would NOT be suitable for identification of bacterial antigens?

Gram Stain Reactions

Match the names of each of the bacterial species with its most likely appearance in the gram stains shown in the photographs.

Campylobacter species A Pseudomonas species B Brucella species C Neisseria species D

The morphology of yeasts inoculated to cornmeal agar can be helpful in making a species identification. The field of view shown in this photomicrograph is most consistent with the identification of:

Candida parapsilosis

Various methods have been employed for detection of C. difficile disease: cultivation of the organism, cell cytotoxin neutralization assays, and enzyme immunoassays have all been among the staples of diagnostic approaches. Which statements are accurate characterizations of these assays?

Cell culture based cytotoxin neutralization assays provide definitive detection of toxin-producing C. difficile strains. Enzyme immunoassays detecting both Toxin A and Toxin B allow the detection of more strains of C. difficile and are therefore preferred over assays that detect only Toxin A.

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

Chocolate agar

This member of the Enterobacteriaceae was isolated from a stool specimen and gave the following biochemical reactions: TSIA . .. . . . . . .K/A, no gas, no H2S Citrate . . . . . . . Positive Lysine . . . . . . . .Negative Ornithine. . . . . . .Positive Indole. . . . . . . . . Negative This organism agglutinated in Group D Shigella antiserum. Which biochemical result is NOT consistent with this identification?

Citrate

Which of the following organisms is most likely to be associated with gas gangrene:

Clostridium perfringens

Infectious disease processes in which large numbers of activated macrophages and histiocytes are collected at the site of inflammation is called:

Granulomatous

Way down under in Brazil, Fever and rash I cause at will.

Haemophilus aegyptius

Within three days at 28 ºC a sputum specimen placed on Sabouraud's dextrose agar with chloramphenicol and cycloheximide produced moist, grayish growth, with a white aerial mycelium, the organism is MOST likely:

Coccidioides immitis

The tendency for the mycobacterial cells of M. tuberculosis to assemble in linear aggregates as seen in this photomicrograph of an acid-fast stained preparation is caused by production of:

Cording factor

The historical medium of choice for isolation of Francisella is:

Cysteine Blood Glucose Agar

A 21 year old female developed painful swelling of the left knee associated with 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 direct gram stain was performed (see photomicrograph). Based on the gram stain morphology, each of the following bacterial species could serve as the etiologic agent in the case described except:

Haemophilus influenzae

I measure 15 micro meters and am found in stool.

Entamoeba histolytica cyst

A small portion of colonial growth of an unknown bacterial species was inoculated to the surface of a filter paper strip impregnated with cytochrome oxidase reagent (dimethyl-p-phenylenediamine dihydrochloride). The family of bacteria ruled out by the reaction seen in the photograph is the:

Enterobacteriaceae

Match the viruses below with their associated diseases.

Epstein-Barr Infectious mononucleosis Varicella-Zoster Chicken pox Rhabdovirus Rabies Picornavirus Polio

Among the gram-positive bacilli, the unique species producing H2S as seen in the Kligler Iron Agar slant illustrated in this photograph is:

Erysipelothrix rhusiopathiae

The pathogenicity of Staphylococcus aureus, as well as the frequency with which this organism produces infections, can be attributed to:

Exfoliative toxin and enterotoxins Natural colonization/reservoir for infection Hyaluronidase

The most important bloodborne pathogens are:

Hepatitis B Hepatitis C HIV All of the above

Match the viruses below with their associated conditions.

Herpesvirus Herpes Papovavirus Warts Rhinovirus Common Cold Rotavirus Gastroenteritis in infants

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

High level gentamicin resistance

Large, one-celled, smooth-to-tuberculate macroconidia, and smooth or echinulate microconidia are typical of mycelial phase growth of which organism?

Histoplasma capsulatum

Viral and rickettsial infections are MOST reliably diagnosed by which laboratory technique?

IFA testing

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

The combination of organisms that is correctly paired with the reactions for appropriate quality control (one organism positive for the reaction and one organism negative for the reaction) are:

Indole: Escherichia coli and Proteus mirabilis

Surprise! Shown in this photograph is a new method for performing MIC susceptibility tests by disk diffusion. The filter paper strip, called the Etest, is impregnated with penicillin in a concentrations gradient of 250 ug/ml to 0.002 ug/ml. The organism being tested is Streptococcus pneumoniae and the MIC reading is 1.0 ug/ml. The strain being tested is:

Intermediate

A diarrheal stool can be suspected of harboring Vibrio cholerae if it:

Is watery with a high pH

In order to identify an isolate as Yersinia enterocolitica, it must be lysine-negative and:

K/A on Kligler's iron agar

Match the illustrations with their correct description:

Monotrichous A Peritrichous B Amphitrichous C

A patient with an upper respiratory infection submits a sputum for culture. A Gram stain performed on the sputum specimen reveals gram-negative diplococci. Oxidase testing is positive and carbohydrate degradation tests are inactive. The organism may presumptively be identified as:

Moraxella catarrhalis

A sputum sample from a patient with pulmonary abscesses is received in the laboratory, and after several days of incubation the following are noted: Yellow, irregular colonies grow on 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

Match the names of each of the bacterial species listed with its distinguishing characteristic listed.

Nocardia species Strict aerobe Lactobacillus species Catalase negative Streptomyces species Musty basement odor Rhodococcus equii Salmon pink colonies

Shigella species generally exhibit which of these characteristics?

Non-motile

Match type of media on the right with media on the left:

Nonselective Blood agar Selective Phenylethylalcohol agar Enrichment Selenite broth

The BEST test to differentiate between Aeromonas hydrophila and E. coli from a wound culture is what?

Oxidase production

A yeast identification system gave a biotype number for an unknown isolate that did not differentiate between Candida tropicalis and Candida parapsilosis. This isolate could be identified as C. parapsilosis in a cornmeal agar preparation if it produced:

Satelliting "cross match stick" or "sage brush" colonies

Match each of the names of the fungi listed in the left column with its most likely associated disease listed in the right column.

Scedosporium apiospermum Chronic sinusitis Aspergillus niger Otitis externa Fusarium species Mycotic keratitis Trichophyton rubrum Tinea pedis

The observation of darkly pigmented colonies on blood 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:

Stenotrophomonas maltophilia

Which of the following species are gram positive:

Streptococcus Listeria Lactobacillus

Which one of the following tests would be positive in the presence of Klebsiella:

Voges-Proskauer test

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

Weak activity

Who am I, a bug so obscene To cause the first quarantine?

Yersinia pestis