Medical Microbiology

Staphylococcus 233

&Toxicoses.Foodpoisoningresultsfromingestionoffoodcontaminated

withenterotoxins.Theonsetafewhoursafteringestiontakestheformof

nausea,vomiting,andmassivediarrhea.

&Mixedforms.Dermatitisexfoliativa(staphylococcalscaldedskinsyn-

drome,Ritterdisease),pemphigusneonatorum,andbullousimpetigoare

causedbyexfoliatin-producingstrainsthatinfecttheskinsurface.Toxic

shocksyndrome(TSS)iscausedbystrainsthatproduceTSST-1.Thesestrains

cancauseinvasiveinfections,butmayalsoonlycolonizemucosa.Themain

symptomsarehypotension,fever,andascarlatiniformrash.

Diagnosis.Thisrequiresmicroscopicandculture-basedpathogenidentifica-

tion.DifferentiatingS.aureusfromthecoagulase-negativespeciesisachieved

bydetectionoftheplasmacoagulaseand/ortheclumpingfactor.Theentero-

toxinsandTSST-1canbedetectedbymeansofimmunologicalandmolecular

biologicalmethods(speciallaboratories).

PlasmaCoagulaseandClumpingFactorTest

&Todetectplasmacoagulase,suspendseveralcoloniesin0.5mlofrabbitplasma,

incubatetheinoculatedplasmaforone,four,and 24 hoursandrecordthelevelsof

coagulation.

&Fortheclumpingfactortest,suspendcolonymaterialinadropofrabbitplasma

onaslide.Macroscopicallyvisibleclumpingconfirmsthepresenceofthefactor.

Therapy.Asidefromsurgicalmeasures,therapyisbasedonadministration

ofantibiotics.Theagentsofchoiceforsevereinfectionsarepenicillinase-

resistantpenicillins,since 70 – 80 %ofallstrainsproducepenicillinase.These

penicillinsare,however,ineffectiveagainstmethicillin-resistantstrains,and

thisresistanceappliestoallbetalactams.

Epidemiologyandprevention.S.aureusisafrequentcolonizerofskinand

mucosa.Highcarrierrates(upto 80 %)aretherulesamonghospitalpatients

andstaff.Theprinciplelocalizationofcolonizationinthesepersonsisthe

anteriornasalmucosaarea,fromwherethebacteriacanspreadtohands

orwithdustintotheairandbetransmittedtosusceptiblepersons.

S.aureusisfrequentlythecausalpathogeninnosocomialinfections(see

p.343f.).Certainstrainsareknowntocausehospitalepidemics.Identification

oftheepidemicstrainrequiresdifferentiationofrelevantinfectionisolates

fromotherubiquitousstrains.Lysotyping(seep. 1 86)canbeusedforthis

purpose,althoughuseofmolecularmethodstoidentifygenomicDNA“fin-

gerprints”isnowbecomingmorecommon.

Themostimportantpreventivemeasureinhospitalsiswashingthehands

thoroughlybeforemedicalandnursingprocedures.Intranasalapplicationof

antibiotics(mupirocin)isamethodofreducingbacterialcountsincarriers.

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Kayser, Medical Microbiology © 2005 Thieme