AFB

Question 1

Desired blood culture volume adults

Answer 1

20-30 mL

Question 2

Desired blood culture volume kids

Answer 2

1-5 mL

Question 3

How long are AFB cultures held for?

Answer 3

6 weeks

Question 4

Define multi-drug resistant TB

Answer 4

resistant to rifampin and isoniazid

Question 5

What are the indications for susceptibility testing of MTB?

Answer 5

1. all initial isolates
2. after 3 months of treatment, culture still positive
3. clinical evidence of treatment failure

Question 6

Treatment of active TB

Answer 6

9 months of isoniazid and rifampin with pyraizinamide for first two months

Question 7

Treatment of latent TB

Answer 7

• Isoniazid for 9 months
• Rifampin for 4 months
• Rifampin/pyrazinamide for 2 months

Question 8

What is the minimum volume for AFB for fluids and respiratory?

Answer 8

1 mL

Question 9

What is the minimum volume for AFB for CSF?

Answer 9

5mL

Question 10

Which mycobacteria species cannot be cultured in vitro?

Answer 10

M. leprae

Question 11

Which bacteria must be worked in under BSL3?

Answer 11

Bacillus anthracis, Yersinia pestis, Franciscella tularensis, Brucella, Chlamydia psittaci, Rickettsia rickettsii, Coxiella burnetti,

Question 12

Which mycobacteria must be worked with in BSL3?

Answer 12

MTB

Question 13

Which parasite must be worked with in BSL3?

Answer 13

Leismania donovani

Question 14

Which viruses must be worked in with BSL3?

Answer 14

West nile virus, Venezuelan equine encephalitis virus, Eastern equine encephalitis virus, SARS coronavirus, Rift Valley fever virus, yellow fever virus

Question 15

Which 4 mycobacteria do we probe for on positive culture?

Answer 15

MTB, MAC, M. kansasii, M. gordonae

Limit of detection 10^1 – 10^2 CFU/mL, sensitivity 85-98%, specificity 97-100%

Question 16

Know key biochemical tests often used to identify M. tuberculosis (niacin/nitrate) and those used to differentiate M. abscessus from M. chelonae (sodium citrate).

Answer 16

• M. tuberculosis: Nitrate (+), Niacin (+)

* M. chelonae can utilize citrate, while M. abscesses cannot

Question 17

First line TB drugs

Answer 17

rifampin, isoniazid, pyrazinamide, ethambutol

Question 18

Second line TB drugs

Answer 18

streptomycin, capreomycin, amikacin, kanamycin, ofloxacin, moxifloxacin, PAS, cycloserine, ethionamide

Question 19

Which mycobacterium are resistant to pyrazinamide?

Answer 19

M. bovis

M. kansassii

Question 20

Define photochromogen

Answer 20

produce pigment after exposure to light
slow growth (>7 days)

Question 21

Which mycobacteria are considered photochromogens?

Answer 21

M. kansasii
M. marinum
M. asiaticum
M. intermedium

Question 22

Define scotochromogen

Answer 22

produce pigment in dark or light, slow growth (>7 days)

Question 23

Which mycobacteria are scotochromogens

Answer 23

M. gordonae

M. scrofulaceum

Question 24

Which mycobacteria are non-photochromogens?

Answer 24

MAC
M. simiae
M. haemophilum
M. xenopi
M. ulcerans
M. malmoense
M. gastri

Question 25

Which mycobacteria are rapid growers?

Answer 25

M. abcessus M. fortuitum M. chelonae

Question 26

Which specimens are digested?

Answer 26

Specimens from non-sterile body sites with normal bacterial and fungal flora, which may interfere with recovery of mycobacteria Vs sterile sites not NaOH: kills competing bacteria Sodium citrate: binds toxic ions produced in digestion N-acetyl-L-cysteine (NALC): mucolytic Oxalic acid is used to kill Pseudomonas in high risk patients (CF)

Question 27

What component of the cell wall is responsible for acid fast staining?

Answer 27

mycolic acid

Question 28

What flouresecent stain is used to ID mycobacteria?

Answer 28

Auramine-rhodamine fluorochrome vs Ziehl-Neelson 10% more sensitive but less specific. Used as screening test

Question 29

Sens and spec mycobacterial cx

Answer 29

Culture limit of detection 10^1 CFU/mL, sensitivity 90-95%, specificity 99%

Question 30

Which AST are routinely done for MAC

Answer 30

clarithromycin, moxifloxacin, and linezolid

Question 31

How does the Gen-Probe accuprobe work?

Answer 31

ssDNDA probe that is complimentary to rRNA target Stable DNA:RNA hybrids are formed Labeled hybrids are measured

Question 32

What does the geneXpert test for

Answer 32

Send out test to state lab | Detects presence of MTBC and RIF resistance