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Unit 6 Chapter 26
Mycobacterium tuberculosis and Other Nontuberculosis Mycobacteria
| Question | Answer |
|---|---|
| Mycobacterium tuberculosis | obligate pathogenic bacterial species in the family Mycobacteriaceae and the causative agent of tuberculosis; the etiologic agent of tuberculosis in humans. Humans are the only reservoir for the bacterium. |
| Mycobacterium bovis | slow-growing aerobic bacterium; etiologic agent of TB in cows and rarely in humans; both cows and humans can serve as reservoirs; humans can also be infected by the consumption of unpasteurized milk. |
| slow growing species of Mycobacterium that are photochromogens | Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium asiaticum, and Mycobacterium simiae. Mycobacterium szulgai is a photochromogen when grown at 24 degrees |
| slow growing species of Mycobacterium that are scotochromogens | Mycobacterium gordonae, Mycobacterium scrofulaceum, Mycobacterium xenopi (ypung cultures may be nonchromogenic . Mycobacterium szulgai is a scotochromogen when grown at 37 degrees |
| rapid growing species of Mycobacterium | Mycobacterium phlei, Mycobacterium smegmatis, Mycobacterium fortuitum, Mycobacterium chelonae, |
| Mycobacterium leprae | also known as Hansen’s bacillus spirilly, mostly found in warm tropical countries, is a Gram-positive bacterium that causes leprosy. It is an intracellular, pleomorphic, acid-fast, pathogenic bacterium |
| Middlebrook mediums | serum albumin-based clear agar media used to support the growth of mycobacteria. |
| Tween 80 test | useful in identifying Mycobacterium kansasii (which can produce positive results within 3-6 hours); to differentiate two scotochromogens with similar appearing colonies, A positive = the liquid, not the cells, light orange to pink or red. |
| Iron Uptake test | distinguses M. chelonae which is negative from rapid growers; used to detect thse mycobacteria capable of converting ferric ammonium citrate to iron oxide |
| Arylsulfatase test | The rate by which arylsulfatase enzyme breaks down phenolphthalein disulfate into phenolphthalein and other salts; used to identify potentially pathogenic rapid growers; Slow growing are positive in the 14 day arylsulfatase test. |
| Pyrazinamidase test | Pyrazinamide (PZA) is an anti-tuberculosis drug M. bovis; used to differentiate between the species, but susceptibility testing becomes complicated, works best at a low pH in vitro; prevents growth of some mycobacteria. |
| Tellurite test | the ability of mycobacterial species to reduce tellurite in 3 to 4 days is used to distinguish members of M. avium complex from most other non-chromogenic species. All rapid growers reduce tellurite in 3 days. |
| Urease test | negative: orange/yellow; positive: bright pink; diamide of carbonic acid, hydrolyzed with release of ammonia & carbon dioxide; ammonia combines w/carbon dioxide & water to form ammonium carbonate; turns medium alkaline, phenol red- orange/yellow-pink |
| NAP test | a precursor in the synthesis of chloramphenicol; selectively inhibits the M. tuberculosis complex. |
| T2H | distinguishes M. bovis from M. tuberculosis; M. bovis is susceptible to lower concentrations of T2H than MTB,; variability in inhibition exists, depending on the concentration of the inhibitory agent and the temperature of incubation |
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