Medical Microbiology

Mycobacterium 269

LeprosyBacteria(LB)..................................

Morphologyandculture.Mycobacteriumleprae(Hansen, 187 3)isthecausa-

tivepathogenofleprosy.Inmorphologicalterms,theseacid-fastrodsare

identicaltotuberculosisbacteria.Theydiffer,however,inthattheycannot

begrownonnutrientmediumsorincellcultures.

Pathogenesis.ThepathomechanismsofLBareidenticaltothoseofTB.The

hostorganismattemptstolocalizeandisolateinfectionfocibyforminggran-

ulomas.Leprousgranulomasarehistopathologicallyidenticaltotuberculous

granulomas.Highcountsofleprosybacteriaareoftenfoundinthemacro-

phagesofthegranulomas.

Immunity.Theimmunedefensesmobilizedagainstaleprosyinfectionare

strictlyofthecellulartype.Theleprominskintestcandetectapostinfectional-

lergy.Thistestisnot,however,veryspecific(i.e.,positivereactionsincasesin

TuberculoidLeprosy

Fig.4. 14 Tuberculoidleprosyisthebenign,nonprogressiveformofthedisease,

characterizedbyspottydermaldepigmentations.

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Kayser, Medical Microbiology © 2005 Thieme