Medical Microbiology

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.

4

Kayser, Medical Microbiology © 2005 Thieme