Medical Microbiology

Mycobacterium 271

Epidemiologyandprevention.Leprosyisnowrareinsociallydeveloped

countries,althoughstillfrequentindevelopingcountries.Thereareanesti-

mated 11 millionvictimsworldwide.Infectedhumansaretheonlysourceof

infection.Thedetailsofthetransmissionpathwaysareunknown.Discussion

ofthetopicisconsideringtransmissionbydirectcontactwithskinormucosa

injuriesandaerogenictransmission.Theincubationperiodis 2 – 5–20years.

Isolationofpatientsundertreatmentisnolongerrequired.Aneffectiveepi-

demiologicalreactionrequiresearlyrecognitionofthediseaseincontactper-

sonsbymeansofperiodicalexaminationseverysixto 12 monthsuptofive

yearsfollowingcontact.

NontuberculousMycobacteria(NTM).................

Mycobacteriathatareneithertuberculosisnorleprosybacteriaarecategor-

izedasatypicalmycobacteria(olddesignation),nontuberculousmycobacte-

ria(NTM)orMOTT(mycobacteriaotherthantuberclebacilli).

Morphologyandculture.Intheirmorphologyandstainingbehavior,NTM

aregenerallyindistinguishablefromtuberculosisbacteria.Withtheexcep-

tionoftherapidlygrowingNTM,theirculturingcharacteristicsarealsosimi-

lartoTB.Somespeciesproliferateonlyat 308 C.NTMarefrequentinhabitants

ofthenaturalenvironment(water,soil)andalsocontributetohumanand

animalmucosalflora.Mostofthesespeciesshowresistancetotheantituber-

culoidagentsincommonuse.

Clinicalpicturesanddiagnosis.SomeNTMspeciesareapathogenic,others

cancausemycobacteriosesinhumansthatusuallyfollowachroniccourse

(Table4. 5 ).NTMinfectionsaregenerallyrare.Theiroccurrenceisencouraged

bycompromisedcellularimmunity.Frequentoccurrenceisobservedto-

getherwithcertainmalignancies,inimmunosuppressedpatientsandin

AIDSpatients,wherebytheNTMisolatedin 80 %ofcasesareM.aviumor

M.intercellulare.Asarule,NTMinfectionsareindistinguishablefromtuber-

culouslesionsinclinical,radiological,andhistologicalterms.Diagnosis

thereforerequiresculturingandpositiveidentification.Theclinicalsignifi-

canceofapositiveresultisdifficulttodetermineduetotheubiquitousoc-

currenceofthesepathogens.Theyarefrequentculturecontaminants.Only

about 10 %ofallpersonsinwhomNTMaredetectedactuallyturnouttohave

amycobacteriosis.

Therapy.Surgicalremovaloftheinfectionfocusisoftenindicated.Che-

motherapydependsonthepathogenspecies,forinstanceatriplecombina-

tion(e.g.,INH,ethambutol,rifampicin)or,forresistantstrains,acombination

offourorfiveantituberculoidagents.

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Kayser, Medical Microbiology © 2005 Thieme