294 4 BacteriaasHumanPathogens&EnterohemorrhagicE.coli(EHEC).Thesebacteriaarethecausative
pathogensinthehemorrhagiccolitis andhemolytic-uremicsyndrome
(HUS)thatoccurinabout 5 %ofEHECinfections,accompaniedbyacuterenal
failure,thrombocytopenia,andanemia.EHECpossessspecific, plasmid-
codedfimbriaeforadhesiontoenterocytes.Theycanalsoproducepro-
phage-determined cytotoxins(shigaliketoxinsorverocytotoxins).Some
authorsthereforedesignatethemasVTEC(verotoxin-producingE.coli).
EHECstrainshavebeenfoundintheOserogroupsO1 57 ,O26,O1 11 ,O145,
andothers.TheserovarmostfrequentlyresponsibleforHUSisO1 57 :H7.
&EnteroaggregativeE.coli(EAggEC).Thesebacteriacausewatery,and
sometimeshemorrhagic,diarrheaininfantsandsmallchildren.Adhesion
toenterocyteswithspecificattachmentfimbriae.Productionofatoxiniden-
ticaltoSTainETEC.
Diagnosis.Extraintestinalinfectionsarediagnosedbyidentifyingthepatho-
geninrelevantmaterials.Diagnosisofaurinarytractinfectionwithmid-
streamurinerequiresdeterminationofthebacterialcounttoensurethat
aninfectioncanbedistinguishedfromacontamination.Counts>– 105 /ml
tendtoindicateaninfection,<– 103 /mlacontamination, 104 /mlcouldgoeither
way.Specificgeneprobesarenowbeingusedtomakeidentificationofin-
testinalpathogenE.colibacterialessdifficult.
Therapy.Antibiotictherapymusttakeintoconsiderationtheresistance
patternofthepathogen.Aminopenicillins,ureidopenicillins,cephalosporins,
4-quinolones,orcotrimoxazoleareusefulagents.Severediarrheanecessi-
tatesoral replacementoffluidandelectrolyte lossesaccordingtothe
WHOformula:3.5gNaCl,2.5gNaHCO 3 , 1 .5gKCl, 20 gglucoseperliterof
water.Whenrequired,intestinalactivityissloweddownwithloperamide.
Epidemiologyandprevention.Transmissionofintestinalinfectionsisusual-
lyindirectviafood,drinkingwater,orsurfacewater.Fiftypercentoftravelers’
diarrheacasesarecausedbyE.coli,inmostcasesETEC.
Themosteffectivepreventivemeasuresagainstintestinalinfections,e.g.,
whentravellingincountrieswithwarmclimates,istoeatonlythoroughly
cookedfoodsanddrinkonlydisinfectedwater.Studieshavedemonstrated
theefficacyofchemoprophylaxiswithanti-infectiveagentsinpreventing
traveler’sdiarrhea,wherebytheagentsusedmustnotreducethenormal
aerobicintestinalflora(4-quinolonesandcotrimoxazolearesuitable).This
methodishardlypracticable,however,inviewofthelargenumbersof
travelers.4
Kayser, Medical Microbiology © 2005 Thieme