Mycobacteria Quiz

Question 1

The best specimen for recovery of 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

Answer 1

a. First morning specimen

Question 2

Mycobacteria stained by Ziehl-Neelsen or Kinyoun methods with methylene blue counter stain 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

Answer 2

a. Bright red rods against a blue background

Question 3

Which of the following mycobacteria produces pigmented colonies in the dark (is a scotochromogen)?

a. M. xenopi
b. M. kansasii
c. M. tuberculosis
d. M. szulgai

Answer 3

d. M. szulgai

Question 4

All of the following mycobacteria are associated with skin infections except:

a. M. marinum
b. M. hemophilum
c. M. kansasii
d. M. ulcerans

Answer 4

c. M. kansasii

Question 5

Mycobacteria isolated from a respiratory culture grew best at 42C. Colonies on LJ medium were not pigmented after exposure to light and negative for niacin accumulation and nitrate reduction. The most likely identification is:

a. M. marinum
b. M. ulcerans
c. M. xenopi
d. M. hemophilum

Answer 5

c. M. xenopi

Question 6

Which of the following mycobacteria is best differentiated by the rapid (w/in 6 hours) hydrolysis of tween 80 ?

a. M. fortuitum
b. M. chelonae
c. M. kansasii
d. M. gordonae

Answer 6

c. M. kansasii

Question 7

An employee of a tropical fish store had a skin infection a finger. The lesion was cultured and grew an acid fast bacilli. The organism grew best at 30C. was nonpigmented when grown in the dark and produced a deep yellow color when exposed to light.

This organism is most likely:

a. M. tuberculosis
b. M. marinum
c. M. xenopi
d. M. ulcerans

Answer 7

b. M. marinum

Question 8

A Mycobacterium species is recovered from a patient with AIDS gave the following results:

Niacin = NEG

Tween 80 hydrolysis = NEG

Nitrate reduction = NEG

Heat stable catalase (68C) = +/-

Non-photochromogen

What is the most likely identification?

a. M. gordonae
b. M. bovis
c. M. avium complex
d. M. kansasii

Answer 8

c. M. avium complex

Question 9

Which nonpathogenic Mycobacterium sp. is isolated most often from clinical specimens and is called the ‘tapwater bacillus’?

a. M. kansasii
b. M. avium complex
c. M. leprae
d. M. gordonae

Answer 9

d. M. gordonae

Question 10

Rapid methods for identifying infection with M. tuberculosis include:

a. HPLC
b. Nucleic acid probes
c. Acid-fast smears
d. All of the above

Answer 10

d. All of the above