Medical Microbiology

Brucella,Bordetella,Francisella 313

Brucella,Bordetella,Francisella

&ThegeneraBrucella,Bordetella,andFrancisellaaresmall,coccoid,Gram-

negativerods.Theycanbeculturedunderstrictaerobicconditionsonen-

richednutrientmediums.

Brucellaabortus,B.melitensis,andB.suiscausebrucellosis,aclassiczoo-

nosisthataffectscattle,goats,andpigs.Thepathogenscanbetransmittedto

humansdirectlyfromdiseasedanimalsorindirectlyinfood.Theycausechar-

acteristicgranulomasintheorgansoftheRES.Theprimaryclinicalsymptom

istheundulantfever.Diagnosisisbymeansofpathogenidentificationor

antibodyassayusingastandardizedagglutinationreaction.

Bordetellapertussisisthecausativeorganismofwhoopingcough,which

affectsonlyhumans.Thepathogensaretransmittedbyaerosoldroplets.The

organismisnotcharacterizedbyspecificinvasiveproperties,althoughitis

abletocauseepithelialandsubepithelialnecrosesinthemucosaofthelower

respiratorytract.Thecatarrhalphase,paroxysmalphase,andconvalescent

phasecharacterizetheclinicalpictureofwhoopingcough(pertussis),which

isusuallydiagnosedclinically.Duringthecatarrhalandearlyparoxysmal

phases,thepathogenscanbeculturedfromnasopharyngealsecretions.

Themostimportantprophylacticmeasureisthevaccinationinthefirst

yearoflife.

Francisellatularensiscausestularemia.Thisdisease,rareinEurope,af-

fectswildrodentsandcanbetransmittedtohumansbydirectcontact,by

arthropodvectors,andbydustparticles. &

Brucella(Brucellosis,Bang’sDisease)

Occurrenceandclassification.ThegenusBrucellaincludesthreemedically

relevantspecies—B.abortus,B.melitensis,andB.suis—besidesanumberof

others.Thesethreespeciesarethecausativeorganismsofclassiczoonoses

inlivestockandwildanimals,specificallyincattle(B.abortus),goats(B.me-

litensis),andpigs(B.suis).Thesebacteriacanalsobetransmittedfromdis-

easedanimalstohumans,causingauniformclinicalpicture,so-calledundu-

lantfeverorBang’sdisease.

Morphologyandculture.Brucellaeareslight,coccoid,Gram-negativerods

withnoflagella.

Theyonlyreproduceaerobically.Intheinitialisolationtheatmosphere

mustcontain 5 – 10 %CO 2 .Enrichedmediumssuchasbloodagararerequired

togrowthemincultures.

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Kayser, Medical Microbiology © 2005 Thieme