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
What is HPLC and how do we use it in the lab?
High performance liquid chromatography; provides an ID based on mycolic acid pattern, analysis of mycolic acids contained within mycobacterial cell walls
How do mycobacteria typically appear in gram stains?
Beaded or ghosted GPR (can look similar to strep)
Name 3 characteristics of M. gordonae
- Found in tap water
- Scotochromogen
- Non-pathogenic
Name 3 characteristics of M. tuberculosis
- Rough and buff
- Slow grower
- Nonchromagen
- Must confirm ID using biochemical methods
Which mycobacteria species deomonstrates candycane striations?
M. kansasii
Requires heme to grow, optimal temperature is 30C generally isolated from immunocomposed individualsq
M. haemophilum
What is the MB bottle (Myco F Lytic) used for?
Liquid medium used for blood, put into Bactec Fx, has heme (CHOC) in media to break apart RBCs to release organism
What is the MP bottle (MGIT) used for?
Liquid medium used for all specimen excepts blood; put into MGIT instrument, clear if uninooulated
Name 2 characteristics of M. kansasii
- “Candy cane” striations
- Photochromogen
What is the 7H10 slant used for?
All purpose, enriched for AFB, clear agar, if from a superficial source a second slant is set up and incubated at 30°C
Purpose of the choclate slant?
Used for specimens rich in heme (BM, blood), incubated at 30C
Purpose of LJ slant?
Lowenstein-Jensen, used in biochemical testing
Function of the 7H10 plate?
Used when isolation of colonies is desired
What PPE is used in the AFB lab
- Gloves
- Gown
- Mask (N95 or better)
- Foot covers
What unique characteristic is seen in M. szulgai?
Colonies are either smooth or rough
What is he media used in the 5% NaCl tolerance test?
LJ slant with 5% NaCl
What are the incubation requirements for the 5% NaCl tolerance test?
Incubated at 35-37C in CO2 up to 4 weeks
