Medical Microbiology

Listeria,Erysipelothrix,andGardnerella 253

Clinicalcharacteristics.Listeriaeareclassicopportunists.Thecourseofmost

infectionsisclinicallysilent.Symptomsresemblingamildfludonotoccurin

immunocompetentpersonsuntillargenumbersofpathogens(1 06 –1 09 )enter

thegastrointestinaltractwithfood.Massiveinfectionsfrequentlycause

symptomsofgastroenteritis.

Listeriosiscantakeontheformofasepsisand/ormeningoencephalitis

inpersonswithTcelldefectsormalignancies,inalcoholics,duringcortisone

therapy,duringpregnancy,inelderlypersonsandininfants.

Connatallisteriosisischaracterizedbysepsiswithmultipleabscessesand

granulomasinmanydifferentorgansoftheinfant(granulomatosisinfan-

tiseptica).

Thelethalityrateinseverecasesoflisteriosisvariesbetween 10 %and 40 %.

Theincubationperiodcanvaryfromonetothreedaystoweeks.

Diagnosisrequirespathogenidentificationbymeansofmicroscopyandcul-

turing.

Therapy.Amoxicillin,penicillinG,orcotrimoxazole.

Epidemiologyandprevention.Listeriaeoccurubiquitouslyinsoil,surface

water,plants,andanimalsandarealsofoundwithsomefrequency(1 0 %)

intheintestinesofhealthyhumans.Despitethefactthatcontactwithlister-

iaeis,therefore,quitenormalandevenfrequent,listeriosisisnotatallcom-

mon.Theincidenceofsevereinfectionsisestimatedatsixcasesper 106 in-

habitantsperyear.Occurrenceisgenerallysporadic.Small-scaleepidemics

causedbyfoodproducts—suchasmilk,milkproducts(cheese),meatpro-

ducts,andotherfoods(e.g.,coleslaw)—contaminatedwithveryhighnum-

bersoflisteriaehavebeendescribed.Preventivemeasuresincludeproper

processingandstorageoffoodproductsinkeepingwithrelevanthygienic

principles.

Erysipelothrixrhusiopathiae..........................

Thisbacteriumisaslender,nonmotile,Gram-positiverod.E.rhusiopathiae

causesasepticdiseaseinpigs,swineerysipelas.Thecorrelateinhumans

isnowquiterareandisarecognizedoccupationaldisease.Followingcontact

withinfectiousanimalmaterial,thepathogensenterbodytissuesthrough

dermalinjuries.Afteranincubationperiodofonetothreedays,theso-called

erysipeloid—ahivelike,bluish-redswelling—developsatthesiteofentry.

Thelymphnodesarealsoaffected.Thesebenigninfectionsoftenhealspon-

taneouslyanddisappearrapidlyundertreatmentwithpenicillinG.Labora-

torydiagnosticproceduresinvolveidentificationofthepathogeninwound

secretionusingthemethodsofmicroscopyandculturing.

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Kayser, Medical Microbiology © 2005 Thieme