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A3 - Microbiology - Harr > 8.8 Mycobacteria > Flashcards

8.8 Mycobacteria Flashcards

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1
Q

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

A. First morning specimen

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2
Q

What concentration 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

A

B. 4% NaOH

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3
Q

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

A

C. Petragnani agar

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4
Q

**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

A. Bright red rods against a blue background

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5
Q

**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

A. Mycobacterium tuberculosis

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6
Q

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

A

D. Mycobacterium bovis

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7
Q

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

A. Mycobacterium fortuitum and Mycobacterium tuberculosis

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8
Q

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

A. Mycobacterium szulgai

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9
Q

All of the following mycobacteria are associated with skin infections except:
A. Mycobacterium marinum
B. Mycobacterium haemophilum
C. Mycobacterium ulcerans
D. Mycobacterium kansasii

A

D. Mycobacterium kansasii

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10
Q

All of the following Mycobacterium spp. produce the enzyme required to convert niacin to niacin ribonucleotide except:
A. Mycobacterium kansaii
B. Mycobacterium tuberculosis
C. Mycobacterium avium complex
D. Mycobacterium szulgai

A

B. Mycobacterium tuberculosis

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11
Q

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

A

D. 30% H2O2 and 10% Tween 80

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12
Q

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

A. Mycobacterium bovis

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13
Q

**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

A

C. Mycobacterium kansasii

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14
Q

Mycobacteria isolated from the hot water system of a hospital grew at 42C. 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

A. Mycobacterium xenopi

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15
Q

A Mycobacterium species recovered from a patient with AIDS gave the following results:
Niacin = Neg
T2H = +
Tween 80 hydrolysis = Neg
Nitrate reduction= 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

A

C. Mycobacterium avium complex

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16
Q

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

A. Mycobacterium gordonae

17
Q

A laboratory provides the following services for identification of mycobacteria: Acid-fast 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

A. Level I

18
Q

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

A

B. Acid-fast staining, inoculation, and referral to a reference laboratory

19
Q

Culture of a skin (hand) wound from a manager of a tropical fish store grew on Lowenstein-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

A. Mycobacterium marinum

20
Q

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

A

D. Mycobacterium gordonae

21
Q

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

A

D. Isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide

22
Q

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

A

D. 6 to 12 months

23
Q

**According to the reporting standards of the ATS, one or more acid-fast bacilli (AFB) per oil immersion field (1,000 x) are reported as: **
A. Numerous or 3+
B. Few or 2+
C. Rare or 1+
D. Indeterminate; a new specimen should be requested

A

A. Numerous or 3+

24
Q

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

A

D. All of the above

25
Q

Rapid methods for identifying classic infection with M. tuberculosis include:
A. Mass spectrometry
B. Nucleic acid probes
C. Acid-fast and fluorochrome-stained smears
D. All of these options

A

D. All of these options

26
Q

Individuals showing a positive purified protein derivative (PPD) skin test for M. tuberculosis are usually:
A. Infective
B. Symptomatic of pulmonary disease
C. Latently infected
D. Falsely positive

A

C. Latently infected

A positive PPD test result indicates a person who is latently infected with M. tuberculosis. Such persons are asymptomatic and not infectious but have a 10% risk of developing tuberculosis during their lifetime.

27
Q

Which of the following Mycobacterium species is diagnosed by means other than culture?
A. Mycobacterium leprae
B. Mycobacterium bovis
C. Mycobacterium canetti
D. Mycobacterium avium

A

A. Mycobacterium leprae

M. leprae and M.microti are different from all other mycobacteria because they cannot be cultured in vitro. Biopsies from nodules and plaques of skin that show numerous AFB are presumptively diagnosed as positive for M. leprae. Confirmatory identification is made by nucleic acid testing (NAT) using PCR.

28
Q

Which M.avium complex organism is the most frequently isolated mycobacterium from patients with AIDS?
A. Mycobacterium avium
B. Mycobacterium intracellulare
C. Mycobacterium scrofulaceum
D. Mycobacterium bovis

A

A. Mycobacterium avium

29
Q

Which mycobacterium of the M. tuberculosis complex fails to grow in culture and has a characteristic “croissant-like” morphology in stained smears?
A. Mycobacterium africanum
B. Mycobacterium microti
C. Mycobacterium bovis
D. Mycobacterium leprae

A

B. Mycobacterium microti

30
Q

**Which two mycobacteria commonly isolated from subcutaneous skin have an optimal growth temperature of 30 C?
A. Mycobacterium haemophilum and Mycobacterium ulcerans
B. Mycobacterium kansasii and Mycobacterium xenopi
C. Mycobacterium gordonae and Mycobacterium avium
D. Mycobacterium simiae and Mycobacterium avium

A

A. Mycobacterium haemophilum and Mycobacterium ulcerans

31
Q

Which mycobacterium is associated with Crohn disease?
A. Mycobacterium. marinum
B. Mycobacterium avium subsp. Mycobacterium paratuberculosis
C. M. fortuitum
D. M. gordonae

A

B. Mycobacterium avium subsp. Mycobacterium paratuberculosis

32
Q

Which temperature range is ideal for the recovery of M. marinum?
A. 24 C to 26 C
B. 30 C to 32 C
C. 42 C to 44 C
D. 44 C to 48 C

A

B. 30 C to 32 C

33
Q

Key biochemical tests used to identify M. tuberculosis are:
A. Niacin, nitrate reduction, growth on thiophene-2-carboxylic acid hydrazide (TCH) (10 mg/mL)
B. Light and dark incubation, Tween 80 hydrolysis
C. Heat resistance, catalase (68 C)
D. Growth on MacConkey and blood agars

A

A. Niacin, nitrate reduction, growth on thiophene-2-carboxylic acid hydrazide (TCH) (10 mg/mL)

34
Q

What report should be given for the results of the following AFB smear?
Number of AFB seen = 2 per 300 fields (1,000 x magnification)
A. 1+
B. 2+
C. 3+
D. Indeterminate; repeat with new specimen

A

D. Indeterminate; repeat with new specimen

35
Q

What vaccine against tuberculosis is available, and what is the source of the vaccine?
A. No vaccine is available
B. BCG - source M. bovis
C. MAC - source M. avium
D. INH - source CDC

A

B. BCG - source M. bovis

A3 - Microbiology - Harr (12 decks)

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