T3: Mycobacterium (PART 2) Flashcards
Special requirements for isolation of M. haemophilum
30-32 C and requires hemin
Advantages of the amplified direct DNA probe for ID of M. tuberculosis in a sputum specimen
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Disadvantages of the amplified direct DNA probe for ID of M. tuberculosis in a sputum specimen
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Runyon Groups:
Group I
Photochromogens
Runyon Groups:
Group II
Scotochromogens
Runyon Groups:
Group III
Nonchromogens
Runyon Groups:
Group IV
Rapid Growers
Sputum Processing for M. tuberculosis
- decontamination methods
- Eliminate normal flora from the non-sterile samples
- homogenization to release the bacteria from the sample and allow access to the nutrient present in the media
- Homogenization: N-acetyl-cystine
- Decontaminant: NaOH
Sputum Processing for M. tuberculosis
- concentration of NaOH
- 2% NaOH is optimal to decontaminate but not kill all the mycobacteria
Centrifugation: 3000-38000 x g or higher
Sputum Processing for M. tuberculosis
- smear staining
AFB stain on smear
Common members in Group I/Photochromogens
M. kansasii M. marinum M. simiae M. genavense M. asiaticum
Common members in Group II/Scotochromogens
M. scrofulaceum M. szulgai M. xenopi M. celatum M. gordonae M. flavescens
Common members in Group III/Nonchromogens
M. avium
M. paratuberculosis
M. terrae
M. haemophilum
Common members in Group IV/Rapid Growers
M. fortuitum
M. chelonae
M. abcessus
Three members of the M. tuberculosis complex
M. tubeculosis
M. africanum
M. bovis
What is the setup of a skin culture for mycobacteria? (include temp, media etc)
EVERYTHING must be set up at 37C with bottle and solid media. Then if it is skin or soft tissue, also set up at 30-32C
Appearance on an agar plate:
- M. tuberculosis
rough and buff
Appearance on an agar plate:
- M. kansasii
buff colored when in the dark and yellow colored when exposed to light
Appearance on an agar plate:
- M. xenopi
pale yellow to yellow orange regardless of light (very slower grower, loves 42C)
Appearance on an agar plate:
- M fortuitum
rapid, rhizoids and rust appearance
M. bovis:
- how does it affect the TB skin test
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M. bovis
- how it is used in cancer patients
BCG treatment in patients with bladder cancer
M. bovis:
- how it is identified
- water doplet-like colonies
- Positive with the TB complex DNA probe
- Susceptibility to T2H
M. bovis
- relationship to BCG
An “attenuated” strain of M. bovis that does not cause disease but can stimulate the immune response is used for the Bacillus Calmette-Guerin (BCG) vaccine
Which mycobacteria are inhibited by T2H?
M. bovis
Which mycobacteria are Nitrate positive?
M. tuberculosis M. kansasii M szulgai M flavescens M fortuitum
How can urease be used as a clue to differentiate scotochromogens into pathogens vs. nonpathogenic
Urease positive means its probably a pathogen, negative urease usually indicates a contaminant
Methods for identifying M. leprae
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Tests that differentiate M. tuberculosis and M. bovis
Niacin, Nitrate, and T2H
M. tuberculosis: Niacin (+), Nitrate (+) T2H (resistant)
M bovis: Niacin (-), Nitrate (-) T2H (susceptible)
Key biochemical reactions for differentiating members of the rapid growers group
MAC and Iron uptake
Key biochemical reactions for differentiating members of the scotochromogens group
Urease and Tween
Key biochemical reactions for differentiating members of the photochromogens group
photochromogenicity and temperature
