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Flashcards in Mycobacteria not TB Deck (11):

The atypical mycobacteria are

environmentally-acquired infections that cause neither TB nor leprosy.


Atypical mycobacterial infection in an immunocomp adult is...; in kids; in immunosuppressed

usually cutaneous;
may have systemic symptoms, particularly from M. kansasii or MAI/C


Atypical mycobacterial infections may be

difficult to treat once established; require multiple antibiotics; (environmental, PPD and TST usually negative, not lethal in guinea pigs);


M leprae has

no in vitro culture system, slowest growing human pathogen, prefers 30C to 37C (humans are major reservoir)


M leprae has extremely long

incubation period (months to 50 yrs), doesn’t transmit easily, only 5-10% of humans believed susceptible to disease (most common sequel of exposure is asymptomatic seroconversion)


Hansen's disease (leprosy) presents

on a range from Tuberculoid (paucibacillary, CD4 and Th1 response, vigorous CMI both contains infection and damages nerves, PPD+) to Lepromatous (multibacillary, Th2, weak CMI, extensive cutaneous symptoms with greater than 6 lesions and also visible bacilli possible; maybe eye infection and leonine facies, PPD-)


Lepromatous easily tested by; tuberculoid may be

skin smear, biopsy, molecular probe, serology; detected by biopsy or serology but sensitivity is low – physical exam, history, &PPD


Lepromin PPD tests

anti-leprosy immunocompetence (Th1 vs Th2), NOT exposure


Treat M leprae with

2yrs dapsone+rifampin


Lepromatous patients may develop

erythema nodosum leprosum, severe cases can require immunomodulant treatment like thalidomide (teratogen!)


Group 1, 2, 3, 4 atypical mycobacteria:

Group 1: photochromogens (M kansasii that resembles TB and killed by same antibiotics; M marinum exposed to fresh and salt water and treated with tetracycline);
Group 2: scotochromogens (makes SCROFULA; reservoir is water)
Group 3: nonchromogens (M avium/M intracellulare that cause pulmonary disease but it's ENVIRONMENTALLY acquired)
Group 4: rapidly growing mycobacteria (these obviously grow fast, and M smegmatis is only normal flora under foreskin)