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MYCO Flashcards

1
Q

The best specimen for recovery of the mycobacteria from a sputum sample is:

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 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

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’s agar
D. American Thoracic Society medium

A

C. Petragnani’s agar

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4
Q

Mycobacteria stained by 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 Middlebrook 7H10 slants produced buff-colored microcolonies with a serpentine pattern after
14 days at 37°C. Niacin and nitrate reduction tests were positive. What is the most probable presumptive identification?

A. Mycobacterium tuberculosis
B. Mycobacterium ulcerans
C. Mycobacterium kansasii
D. Mycobacterium avium-intracellulare 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-intracellulare 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?

A. Mycobacterium fortuitum and Mycobacterium
tuberculosis
B. Mycobacterium avium-intracellulare 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. M. szulgai
B. M. kansasii
C. M. tuberculosis
D. All of these options

A

A. M. 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. M. kansasii
B. M. tuberculosis
C. M. avium-intracellulare complex
D. M. szulgai

A

B. M. 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 specie?

A. M. bovis
B. M. avium-intracellulare complex
C. M. kansasii
D. M. marinum

A

A. M. bovis

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13
Q

Which of the following Mycobacterium spp. is best differentiated by the rapid hydrolysis of Tween 80?

A. M. fortuitum
B. M. chelonae
C. M. kansasii
D. M. gordonae

A

C. M. kansasii

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14
Q

Mycobacteria isolated from the hot water
system of a hospital grew at 42°C. Colonies on 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
Tween 80 hydrolysis = Neg Heat-stable catalase (68°C) = ±
Nonphotochromogen
T2H = +
Nitrate reduction = Neg

What is the most likely identification?

A. M. gordonae
B. M. bovis
C. M. avium-intracellulare complex
D. M. kansasii

A

C. M. avium-intracellulare complex

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16
Q

The urease test is needed to differentiate Mycobacterium scrofulaceum from which of the following mycobacteria?

A. M. gordonae
B. M. kansasii
C. M. avium-intracellulare complex
D. M. bovis

A

A. M. 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 American Thoracic Society’s definition for levels of service this laboratory is:

A. Level I
B. Level II
C. Level III
D. Level IV

A

B. Level II

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 Mycobacterium 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 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
Heat-stable catalase (68°C) = Neg
Nitrate reduction = Neg
Tween 80 hydrolysis = +
Urease = +

A. Mycobacterium marinum
B. Mycobacterium kansasii
C. Mycobacterium avium-intracellulare complex
D. Mycobacterium tuberculosis

A

A. Mycobacterium marinum

20
Q

Which nonpathogenic Mycobacterium specie is isolated most often from clinical specimens and is called the “tapwater bacillus”?

A. M. kansasii
B. M. avium-intracellulare complex
C. M. leprae
D. M. gordonae

A

D. M. 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. Isonicotinic acid hydrazide (INH), rifampin, ethambutol, and pyrazinamide

A

D. Isonicotinic acid hydrazide (INH), rifampin, ethambutol, and pyrazinamide

22
Q

How long should Mycobacterium tuberculosis-positive cultures be kept by the laboratory after identification and antibiotic susceptibility testing have been performed?

A. 1-2 months
B. 2-4 months
C. 5-6 months
D. 6-12 months

A

D. 6-12 months

23
Q

According to the reporting standards of the American Thoracic Society, 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

A. Numerous or 3+

24
Q

Which of the following Mycobacterium spp. would be most likely to grow on a MacConkey agar plate?

A. M. chelonae-fortuitum complex
B. M. ulcerans
C. M. marinum
D. M. avium-intracellulare complex

A

A. M. chelonae-fortuitum complex

25
Q

Rapid methods for identifying classic infection with M. tuberculosis include:

A. Gas-liquid chromatography
B. Nucleic acid probes
C. Acid-fast 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

27
Q

Which of the following Mycobacterium species is diagnosed by means other than culture?

A. M. leprae
B. M. bovis
C. M. canetti
D. M. avium

A

A. M. leprae

28
Q

Which M. avium complex (MAC) organism is the most frequently isolated mycobacterium from AIDS patients?

A. M. avium
B. M. intracellulare
C. M. scrofulaceum
D. M. bovis

A

A. M. 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. M. africanum
B. M. microti
C. M. bovis
D. M. leprae

A

B. M. microti

30
Q

Which two mycobacteria commonly isolated from subcutaneous skin have an optimal growth temperature of 30°C?

A. M. haemophilum and M. ulcerans
B. M. kansasii and M. xenopi
C. M. gordonae and M. avium
D. M. simiae and M. avium

A

A. M. haemophilum and M. ulcerans

31
Q

Which mycobacterium is associated with Crohn’s disease?

A. M. marinum
B. M. paratuberculosis
C. M. avium
D. M. gordonae

A

B. M. paratuberculosis

32
Q

Which temperature range is ideal for the recovery of M. marinum?

A. 24°C-26°C
B. 30°C-32°C
C. 42°C-44°C
D. 44°C-48°C

A

B. 30°C-32°C

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