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Microbiology Module 2 > T3: AFB Lab Practical > Flashcards

T3: AFB Lab Practical Flashcards

0
Q

Nucleic acid probes are available for which mycobacterium species?

A

M. Tuberculosis, M. avium-intracellulare complex, M. gordonae, M. kansasii

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1
Q

Requires heme to grow, optimal temp is 30’C, generally Isolated from immunocompromised individuals

A

M. Haemophilum

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2
Q

List three characteristics of Nocardia

A

Gram-positive, modified acid-fast stain positive (Red), Kinyoun acid-fast stain neg (blue)

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3
Q

Never produces pigment

A

Nonchromogen

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4
Q

Produces pigment only after exposure to light

A

Photochromogen

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5
Q

Produces pigment independent of light exposure

A

Scotochromogen

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6
Q

What reagent must be added to a negative nitrate test? Why?

A

Negative must be confirmed by adding zinc dust. You add zinc just to confirm nitrogen gas. (Clear=pos, Red=neg)

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7
Q

Niacin accumulation test is used to differentiate between which two mycobacterial species?

A

M. tb (+, yellow) and M. bovis (-, no color change)

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8
Q

Name there characteristics of M. Mucogenicum

A

Rapid grower, partially acid-fast, non-chromogen, wet/mucoid looking colonies

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9
Q

How is Kinyoun stain interpreted?

A

Red=positive, blue/purple=negative

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10
Q

The phenomenon known as cording is observed in which mycobacterium species?

A

M. Tuberculosis=virulent

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11
Q

Name 3 characteristics of M. Marinum

A

Grows at 28°C, cutaneous infection associated with fish tanks or salt water, photo chromogen

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12
Q

What type of stain is the auramine-rhodamine (AR) stain? List some advantages and disadvantages

A

Fluorochrome stain
A: most sensitive stain, stains both viable and nonviable organisms, performed directly on specimens
D: won’t stain rapid growers

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13
Q

What reagents are used in the N-acetyl-L-cysteine method of decontamination?

A

N-acetyl-L-cysteine, NaOH, Sodium citrate, neutralizing buffer, phenol red

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14
Q

Purpose of N-acetyl-L-cysteine

A

Works as a mucolytic agent

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15
Q

Function of NaOH

A

Functions as a bacterial decontaminant

16
Q

Function of sodium citrate

A

Binds to heavy metals in the specimen

17
Q

Function of neutralizing buffer

A

Stabilizes the pH and stops the decontamination process

18
Q

Function of phenol red

A

Present in the digestion solution to monitor pH

19
Q

How is a semi-quantitative catalase test interpreted?

A

Column >or equal to 45mm is positive, <45mm is negative

20
Q

Incubation requirements for MAC w/o crystal violet

A

Ambient air at 28 to 30°C for 7 days

21
Q

Which two mycobacterial species is the sodium chloride tolerance test useful in identifying? Results?

A

M. Abscessus (+) and M. chelonae (-)

22
Q

Incubation requirements for the tween-80 hydrolysis test?

A

35 to 37°C ambient air for 10 days

23
Q

How is the tween-80 hydrolysis test interpreted?

A

Pink/red=positive, orange/no color change=negative

24
Q

What is HPLC and how do we use it in the lab?

A

High performance liquid chromatography; provides an ID based on mycolic acid pattern, analysis of mycolic acids contained within mycobacterial cell walls

25
Q

How do mycobacteria typically appear in gram stain?

A

Beaded it ghosted GPR (can look similar to strep)

26
Q

List three characteristics of M. gordonae

A

Found in tap water, scrotochromogen, not a pathogen

27
Q

Three characteristics of M. tuberculosis

A

Rough and buff, slow grower, non-chromogen, must confirm ID using biochemical methodS

28
Q

Which mycobacterium species demonstrates candycane striations?

A

M. Kansasii

29
Q

What is the MB Bottle used for?

A

Liquid medium used for blood, put into bacT alert instrument, has heme (choc) in media to break apart RBCs to release organism

30
Q

What is the MP Bottle used for?

A

Liquid medium used for all specimen except blood, put into BacT alert instrument, clear if uninoculated

31
Q

What is 7H10 slant used for?

A

All purpose, enriched for AFB, clear agar, if from a superficial source a second slant is set up and incubated at 30°C

32
Q

Purpose of chocolate slant?

A

Used for specimens rich in heme (BM, blood), incubated at 30°C

33
Q

Purpose of LJ slant?

A

Lowenstein-Jensen, used in biochemical testing

34
Q

Function of 7H10 plate?

A

Used when isolation of colonies is desired

35
Q

What PPE is used in the AFB lab?

A

Gloves, down, mask (N95 or better), foot covers

36
Q

What unique characteristic is seen in M. szulgai?

A

Smooth or rough colonies, nitrate positive, scotochromogen at 37°C, photochromogen at 25°C

37
Q

Remember…modified acid fast is a weaker decolorizer (partially acid fast) whereas Kinyoun positive is for _____ A-F organisms

Microbiology Module 2 (19 decks)

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