Micro 8.8 Mycobacteria Flashcards
- The best specimen for recovery of the mycobacteria from a sputum sample is the:
A. First morning specimen
B. 10-hour evening specimen
C. 12-hour pooled specimen
D. 24-hour pooled specimen
A. First morning specimen
- What concentration of sodium hydroxide (NaOH) is used to prepare a working decontamination solution for the processing of not normally sterile specimens for mycobacteria?
A. 1% NaOH
B. 4% NaOH
C. 8% NaOH
D. 12% NaOH
B. 4% NaOH
- Which is the most appropriate nonselective medium for recovery of mycobacteria from a heavily contaminated specimen?
A. Löwenstein-Jensen agar
B. Middlebrook 7H10 agar
C. Petragnani agar
D. American Thoracic Society (ATS) medium
C. Petragnani agar
- Mycobacteria stained by using the Ziehl-Neelsen or Kinyoun methods with methylene blue counterstain are seen microscopically as:
A. Bright red rods against a blue background
B. Bright yellow rods against a yellow background
C. Orange-red rods against a black background
D. Bright blue rods against a pink background
A. Bright red rods against a blue background
- Acid-fast staining of a smear prepared from digested sputum showed slender, slightly curved, beaded, red mycobacterial rods. Growth on the Middlebrook 7H10 medium slants produced buff-colored microcolonies with a serpentine pattern after 14 days at 37°C. Niacin and nitrate reduction test results were positive. What is the most probable presumptive identification?
A. Mycobacterium tuberculosis
B. Mycobacterium ulcerans
C. Mycobacterium kansasii
D. Mycobacterium avium complex
A. Mycobacterium tuberculosis
- Which organism, associated with tuberculosis in cattle, causes tuberculosis in humans, especially in regions where dairy farming is prevalent?
A. Mycobacterium avium complex
B. Mycobacterium kansasii
C. Mycobacterium marinum
D. Mycobacterium bovis
D. Mycobacterium bovis
- Which of the following organisms are used as controls for rapid growers and slow growers, respectively?
A. Mycobacterium fortuitum and Mycobacterium tuberculosis
B. Mycobacterium avium complex and Mycobacterium tuberculosis
C. Mycobacterium chelonei and Mycobacterium fortuitum
D. Mycobacterium kansasii and Mycobacterium tuberculosis
A. Mycobacterium fortuitum and Mycobacterium tuberculosis
- Which of the following Mycobacterium spp. produce(s) pigmented colonies in the dark (is a scotochromogen)?
A. Mycobacterium szulgai
B. Mycobacterium kansasii
C. Mycobacterium tuberculosis
D. All of these options
A. Mycobacterium szulgai
- All of the following mycobacteria are associated with skin infections except:
A. Mycobacterium marinum
B. Mycobacterium haemophilum
C. Mycobacterium ulcerans
D. Mycobacterium kansasii
D. Mycobacterium kansasii
- All of the following Mycobacterium spp. produce the enzyme required to convert niacin to niacin ribonucleotide except:
A. Mycobacterium kansasii
B. Mycobacterium tuberculosis
C. Mycobacterium avium complex
D. Mycobacterium szulgai
B. Mycobacterium tuberculosis
- The catalase test for mycobacteria differs from that used for other types of bacteria by using:
A. 1% H2O2 and 10% Tween 80
B. 3% H2O2 and phosphate buffer, pH 6.8
C. 10% H2O2 and 0.85% saline
D. 30% H2O2 and 10% Tween 80
D. 30% H2O2 and 10% Tween 80
- Growth inhibition by thiophene-2-carboxylic hydrazide (T2H) is used to differentiate M. tuberculosis from which other Mycobacterium species?
A. Mycobacterium bovis
B. Mycobacterium avium complex
C. Mycobacterium kansasii
D. Mycobacterium marinum
A. Mycobacterium bovis
- Which of the following Mycobacterium spp. is best differentiated by the rapid hydrolysis of Tween 80?
A. Mycobacterium fortuitum
B. Mycobacterium chelonae
C. Mycobacterium kansasii
D. Mycobacterium gordonae
C. Mycobacterium kansasii
- Mycobacteria isolated from the hot water system of a hospital grew at 42°C. Colonies on the Löwenstein-Jensen medium were not pigmented after exposure to light and were negative for niacin accumulation and nitrate reduction. The most likely identification is:
A. Mycobacterium xenopi
B. Mycobacterium marinum
C. Mycobacterium ulcerans
D. Mycobacterium haemophilum
A. Mycobacterium xenopi
- A Mycobacterium species recovered from a patient with AIDS gave the following results:
Niacin = Neg
T2H = +
Nitrate reduction = Neg
Tween 80 hydrolysis = Neg
Heat-stable catalase (68°C) = ±
Nonphotochromogen
What is the most likely identification?
A. Mycobacterium gordonae
B. Mycobacterium bovis
C. Mycobacterium avium complex
D. Mycobacterium kansasii
C. Mycobacterium avium complex
With the exception of M. tuberculosis, M. avium complex is the Mycobacterium species most often isolated from patients with AIDS. It is biochemically inert, which is a distinguishing factor for identification. M. avium complex is highly resistant to the antibiotics used to treat tuberculosis, including those used in multidrug therapy. Treatment with streptomycin, rifampin, ethionamide, ethambutol with cycloserine, or kanamycin has shown little success.
- The urease test is needed to differentiate M. scrofulaceum from which of the following mycobacteria?
A. Mycobacterium gordonae
B. Mycobacterium kansasii
C. Mycobacterium avium complex
D. Mycobacterium bovis
A. Mycobacterium gordonae
- A laboratory provides the following services for identification of mycobacteria:
-Acidfast staining of clinical specimens Inoculation of cultures
-Shipment of positive cultures to a reference laboratory for identification
According to the ATS’s definition for levels of service, this laboratory is:
A. Level I
B. Level II
C. Level III
D. Level IV
A. Level I
The ATS recognizes three levels of laboratory services for mycobacteria testing. Level I laboratories are those that grow mycobacteria and perform acid-fast stains but do not identify M. tuberculosis (they may or may not perform drug susceptibility tests
on M. tuberculosis). Level II laboratories perform all of the functions of Level I laboratories and also identify M. tuberculosis. Level III laboratories identify all mycobacteria species from clinical specimens and perform drug susceptibility tests on all species.
- According to the College of American Pathologists (CAP) guidelines, which services for mycobacteria would be performed by a Level II laboratory?
A. No procedures performed
B. Acid-fast staining, inoculation, and referral to a reference laboratory
C. Isolation and identification of M. tuberculosis; preliminary identification of other species
D. Definitive identification of all mycobacteria
B. Acid-fast staining, inoculation, and referral to a reference laboratory
- Culture of a skin (hand) wound from a manager of a tropical fish store grew on Löwenstein-Jensen agar slants at 30°C in 10 days but did not grow on the same media at 37°C in 20 days. Given the following results, what is the most likely identification?
Photochromogen = +
Niacin = Neg
Urease = +
Heat-stable catalase (68°C) = Neg
Nitrate reduction = Neg
Tween 80 hydrolysis = +
A. Mycobacterium marinum
B. Mycobacterium kansasii
C. Mycobacterium avium complex
D. Mycobacterium tuberculosis
A. Mycobacterium marinum
- Which nonpathogenic Mycobacterium species is isolated most often from clinical specimens and is called the “tapwater bacillus”?
A. Mycobacterium kansasii
B. Mycobacterium avium complex
C. Mycobacterium leprae
D. Mycobacterium gordonae
D. Mycobacterium gordonae
- Which of the following drugs are first-line antibiotics used to treat classic tuberculosis for which susceptibility testing is performed by the disk diffusion method on Middlebrook 7H10 or 7H11 agar plates?
A. Ampicillin, penicillin, streptomycin, and carbenicillin
B. Ampicillin, penicillin, and methicillin
C. Vancomycin, methicillin, and carbenicillin
D. Isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide
D. Isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide
- How long should M. tuberculosis–positive cultures be kept by the laboratory after identification and antibiotic susceptibility testing have been performed?
A. 1 to 2 months
B. 2 to 4 months
C. 5 to 6 months
D. 6 to 12 months
D. 6 to 12 months
- According to the reporting standards of the ATS, one or more acid-fast bacilli (AFB) per oil immersion field (1,000×) are reported as:
A. Numerous or 3+
B. Few or 2+
C. Rare or 1+
D. Indeterminate; a new specimen should be requested
A. Numerous or 3+
- Which of the following rapid-growing Mycobacterium spp. would most likely grow on a MacConkey agar plate and on other routine bacteriologic media?
A. Mycobacterium chelonae
B. Mycobacterium fortuitum
C. Mycobacterium abscessus
D. All of the above
D. All of the above