AFB Practical #1 Flashcards
What species of mycobacteria are nucleic acid probes available for?
- M. tuberculosis complex
- M. avium complex
- M. gordonae
- M. kansasii
List 3 characeristics of Nocardia sp.
- Often appear powdery white due to production of aerial hyphae
- Branching GPR
- Partially acid fast
Nocardia sp.
- Modified acid-fast stain
- Kinyoun acid-fast stain
- Modified acid-fast stain positive (red)
- Kinyoun acid-fast stain negative (blue)
What is a confirmation test for M. tuberculosis and M. bovis?
Nitrate test
- M. tuberculosis (+)
- M. bovis (-)
What reagent must be added to a negative nitrate test? Why?
Addition of zinc dust confirms nitrogen gas
Niacin accumulation test is used to differentiate b/w which two mycobacterial species?
- M. tuberculosis (+)
- M. bovis (-)
Name 4 characteristics of M. mucogenicum
- Rapid grower
- Partially acid-fast
- Nonchromogen
- Wet/mucoid looking colonies
How is Kinyoun stain interpreted?
- Pos: red
- Neg: blue/purple
Known as the “cold” carbolfuschin-based stain
Kinyoun
The phenomenon known as cording is observed in which mycobacterium species?
M. tuberculosis (virulent factor)
Name 3 characteristics of M. marinum
- Grows at 28C
- Cutaneous infection associated w/ fish tanks or salt water
- Photochromogen
What type of stain is the auramine-rhodamine (AR) stain?
Fluorochrome stain
What are the advantages fo the AR stain?
- Most sensitive stain
- Stains both viable and nonviable organisms
- Performed directly on specimens
What are the disadvantages of the AR stain?
Won’t stain rapid growers
What reagents are used in the N-acetyl-L-cysteine method of decontamination?
- N-acetyl-L-cysteine
- NaOH
- Sodium citrate
- Neutralizing buffer
- Phenol red
N-acetyl-L-cysteine
- Purpose of N-acetyl-L-cysteine
Works as a mucolytic agent
N-acetyl-L-cysteine
- Function of NaOH
Functions as a bacterial decontaminant
N-acetyl-L-cysteine
- Function of sodium citrate
Binds to heavy metals in the specimen
N-acetyl-L-cysteine
- Function of neutralizing buffer
Stabilizes the pH and stops the decontamination process
N-acetyl-L-cysteine
- Function of phenol red
Present in the digestion solution to monitor pH
Incubation requirements for MAC w/o crystal violet
Ambient air @ 28-30°C for 7 days
Which two mycobacterial species is the sodium chloride tolerance test useful in identifying? Results?
- M. abscessus (+)
- M. chelonae (-)
Incubation requirements for the Tween 80 hydrolysis test
Ambient air @ 35-37°C for 10 days
How is the Tween 80 hydrolysis test interpreted?
- Pos: pink/red
- Neg: orange/no color change