Medical Microbiology

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318 4 BacteriaasHumanPathogens

destroytissues(hyaluronidase,collagenase,neuraminidase).Gram-negative
anaerobesarealmostneverthesolepathogensinaninfectionfocus,butare
ratherfoundtheretogetherwithotheranaerobesandaerobes.
Theclinicalcourseofinfectionsissubacutetochronic.Necroticabscesses
areseenfrequently.ThecompartmentsinfectedaretheCNS,theoralcavity,
theupperandlowerrespiratorytract,theabdominalcavity,andtheurogen-
italtract(Table4. 11 ).Thesepathogenscaninfectwoundsfollowingbitein-
juriesorsurgeryinareascolonizedbythem(intestine,oralcavity,genital
tract).
Diagnosisrequiresisolationandidentityofthebacteriainvolved.Sincethese
anaerobesarecomponentsofnormalflora,correctsamplingtechniquesare
veryimportant.Thematerialmustbetransportedinspecialanaerobecon-
tainers.Culturesshouldalwaysbegrownunderbothanaerobicandaerobic
conditions.Selectiveculturemediumsareavailable.Identificationisbasedon
morphologicalandphysiologicalcharacteristics.Gaschromatographycanbe
usedfororganicacidassays(butyricacid,aceticacid,propionicacid,etc.).
Theseacidsareproducedasfinalproductsofcertainbacterialmetabolic
steps.
Therapy.Penicillin,usuallyincombinationwithabetalactamaseinhibitor,
clindamycin,cefoxitin,imipenem,andnitroimidazolesarepotentiallyeffec-
tiveantibiotics.Resistancetestingisonlynecessaryincertaincases.

MixedAnaerobicFlora
Fig.4. 22 Gramstainingofapleural
punctatepreparation:Gram-nega-
tive, fusiform, pleomorphic, and
coccoid rods. Clinical diagnosis:
pleuralempyema.

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Kayser, Medical Microbiology © 2005 Thieme
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