Medical Microbiology

Listeria,Erysipelothrix,andGardnerella 251

Clostridiumdifficile(PseudomembranousColitis)...

C.difficileoccursinthefecalfloraof 1 – 4 %ofhealthyadultsandin 30 – 50 %of

childrenduringthefirstyearoflife.Thefactorsthatleadtodevelopmentof

thediseasearenotknownwithcertainty.Casesofpseudomembranouscolitis

areobservedfrequentlyundertreatmentwithclindamycin,aminopenicillins,

andcephalosporins(hencethedesignationantibiotic-associatedcolitis),

butalsooccurinpersonsnottakingantibiotics.Occasionaloutbreaksare

seeninhospitals.Thepathologicalmechanismisbasedonformationof

twotoxins.ToxinAisanenterotoxinthatcausesadysfunctioncharacterized

byincreasedsecretionofelectrolytesandfluids.ToxinBisacytotoxinthat

damagesthemucosaofthecolon.

Theclinicalcourseincludesfever,diarrhea,andspasmodicabdominal

pains.Coloscopyrevealsedematouschangesinthecolonmucosa,which

isalsocoveredwithyellowish-whitishmatter.Laboratorydiagnosisin-

volvesculturingthepathogenfrompatientstoolanddetectionofthecyto-

toxininbacteria-freestoolfiltratesonthebasisofacytopathiceffect(CPE)

observedincellcultures,whichCPEisthennolongerobservedafterneutra-

lizationwithanantiserum.ToxinsAandBcanalsobedetectedwithimmu-

nologicaltestkits(ELISAtests,seep. 12 7f.).Aspecifictherapyisnotrequired

inmanycases.Antibiotictreatmentisindicatedinseverecases.Theagentof

choiceiscurrentlymetronidazole.

Listeria,Erysipelothrix,andGardnerella...........................

&ListeriamonocytogenesarediminutiveGram-positiverodswithperitri-

chousflagellationthatarequitemotileat 208 Candcanbeculturedaerobi-

callyonbloodagar.Theyoccurubiquitouslyinnature.Humaninfectionsmay

resultif 106 –1 09 pathogensenterthegastrointestinaltractwithfood.Listeriae

areclassicopportunists.Inimmunocompetentpersons,aninfectionwill

eitherbeclinicallysilentorpresentthepictureofamildflu.Inimmunocom-

promisedpatients,thediseasemanifestsasaprimarysepsisand/ormenin-

goencephalitis.Morerarely,listeriaecauseendocarditis.Listeriosisduring

pregnancymayresultinspontaneousabortionorconnatallisteriosis(gran-

ulomatosisinfantiseptica).Penicillins(amoxicillin)andcotrimoxazole,some-

timesincombinationwithaminoglycosides,areusedintherapy.Listeriosisis

arareinfectioncharacterizedbysporadicoccurrence.Occasionalgastroin-

testinalepidemicsduetocontaminatedfoodmayresultfromthecoincidence

ofunfortunatecircumstances.

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Kayser, Medical Microbiology © 2005 Thieme