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tb biochemical test Flashcards

1
Q

Biochemical testing

A

growth rate, morphology, pigment, biochem profiles

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2
Q

arylsulfatase

A

ability to produce detectable level of phenolphthalein after cleaving sulfate group (from aromatic ring
three-day- m. fortuitum+ M.phlei-
M. xenopi produced at 42, MAC doesn’t
14 day- arylsulfatase M.triviale + / M.terrae -

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3
Q

catalase 4 groups

A

1) devoid
2) produce 45 mm
4) lose activity when heated at 68 for 20 min

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4
Q

semi-quantitaivie catalase

A

incubate 2 weeks at 37
1 ml diluted h202 is added
measure heightof effervescence
MTB is negative

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5
Q

Heat-stable catalase

A

heating at 68 c for 20 minutes inactivates
mtb, m. gastri, m. haemophilum
distinguish mtb from other slow growers when niacin is weakly positive

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6
Q

iron uptake

A

capable of converting ferric ammonium citrate to iron oxide
key for rapid growers
M. fortuitum + vs. M. chelonae -

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7
Q

5% NaCl

A

most rapid growers and M. triviale
two LJ slants one regular one with 5% Nacl
M. fortuitum, M. abscessus, M. flavescens +
M. gordonae, M. chelonae -

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8
Q

Niacin

A

mtb accumulates a large amount of niacin
differentiate M. tb+ / M. bovis -
Cyanogen bromide HAZARDOUS neutralize with 10% NaOH

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9
Q

NItrate

A

ability of some mycobacteria to reduce nitrate
most rapid growers have the enzyme except M. chelonae and M. abscessus
M. bovis is nitrate negative vs. M. tb
incubate culture with 2 ml of buffer for 2 hrs

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10
Q

Tween Hydrolysis

A 
hydrolysis of tween 80
differentiate pathogens from saprophytic 
scoto and photochromogens
M. kansasii +
M. gordonae +w
M. bovis and M. avium -
enzyme cleaves oleic acid from tween 80
freeing the indicator dye and turning the solution red
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11
Q

Tween Opacity

A

oleic acid are released from tween80

differentiates M. flavescens + from other slow growers

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12
Q

Urease

A

results in alkalinzation of the medium
all scoto except m. gordonae, m. kansasii, MTBC, m. gastri
mac, m. gordonae, m. xenopi are negative

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13
Q

tellurite reduction

A

potassium tellurite can be reduced to metallic tellurium
7H9 broth is inoculated with test culture, incubate for 10 days, 0.2% KTel solution added, incubate an additional 3 days
mac and most rapid growers are positive
MTB is negative

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14
Q

growth on macconkey w/o crystal violet

A

pathogen (+) vs. saprophytes (-)

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15
Q

Carbon utilization

A

sodium citrate, inositol, mannitol
sole source of carbon in presence of ammoniacal nitrogen
m. chelonae and m. fortuitum

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16
Q

Pyrazinamide Hydrolysis

A

PZA deaminated in some mycobacteria by pyrazinamidase
ferrous ammonium sulfate is added at days 4 and 7
results in pink band after incubation for 30 min
MTB v. M. bovus
M. kansasii - 4 / + 7 vs. M. marinum +4

17
Q

HPLC

A

ID of mycobacteria based on mycolic acid analysis

18
Q

HPLC principle

A

1) extraction of fatty acids
2) separation of esters by column
3) detection by UV or FL detector
4) Visual or mathematical analysis

19
Q

Saponification reagent

A

potassium hydroxide, methanol, water

20
Q

HPLC componens

A 
sample in mobile phase
injector
column
detector
recorder
21
Q

column

A

sorbet(active component of the column
granular material made of solid particles
separate due to different degrees of interaction with sorbent particles

22
Q

Gen-Probe Accuprobe steps

A 
Saponification
Heat Killing
Hybridization
Selection
Detection
POSITIVE & NEGATIVE WITH EACH ASSAY
23
Q

Gen-Probe organisms

A

MTB complex
MAC
M. kansasii
M. gordonae

24
Q

PCR

A

nucleic acid amplification- amply a single or few copies of a piece of DNA generating millions of copies of a particular sequence
denaturation (94)
annearling (50-65)
extension (72)

25
Q

Roche “Amplicor”

A

Biotin-Avidin labeled

spectrophotometer

26
Q

GenProbe MTD

A

transcription-mediated amplification
two enzyme RNA polymerase & reverse transcriptase
LIVE OR DEAD ORGANISMS

27
Q

Cepheid GeneXpert

A

semi-quantitative nested real-time PCR assay
detects presence of MTB complex DNA
and Rifampin resistnace rpoB gene
automated
5 molecular probes which target the rpoB region

28
Q

rpoB

A

95-98% of RIF-Resistant strains have mutation in rpoB gene
most RIF strains are also resistant to Isoniazid
can be used as a tool for early detection of MDR TB

29
Q

RFLP-DNA Fingerprint

A

Restriction Fragment Length Polymorphism
DNA fingerprinting
IS6110 IN THE MTB GENOME
creates 1000 fragment of various sequences/lengths
useful nosocomial, confirming re-infection, identifying unrecognized transmission, cross-contamination, hospital-nursing home

30
Q

DNA sequencing

A

16S rRNA is amplified and determined

differentiate MTB from M. bovis

state exam (9 decks)

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