Medical Microbiology

210 3 GeneralBacteriology

Materialfromtheurogenitaltract:

— Urine.Midstreamurineisinmostcasescontaminatedwiththefloraofthe

anteriorurethra,whichoftencorrespondstothepathogenspectrumof

urinarytractinfections.Bacterialcountsmustbedeterminedif“contam-

ination”istobeeffectivelydifferentiatedfrom“infection.”Atcountsin

morningurineof>– 105 /mlaninfectionishighlyprobable,atcountsof

<– 103 ratherimprobable.Atcountsofaround 104 /mlthetestshouldbe

repeated.Lowercountsmayalsobediagnosticallysignificantinurethro-

cystitis.Thedipstickmethod,whichcanbeusedinanymedicalpractice,is

asimplewayofestimatingthebacterialcount:astickcoatedwithnutri-

entmediumisimmersedinthemidstreamurine,thenincubated.Thecol-

onycountisthenestimatedbycomparingtheresultwithstandardized

images.

— Catheterizingtheurinarybladdersolelyfordiagnosticpurposesisinad-

visableduetothepotentialforiatrogenicinfection.Uncontaminatedblad-

derurineisobtainableonlybymeansofasuprapubicbladderpuncture.

— Genitalsecretionsaresampledwithsmearswabsandmustbetrans-

portedinspecialtransportmediums.

Blood:

— Forabloodculture,atleast 10 – 20 mlofvenousbloodshouldbedrawn

sterilelyintooneaerobicandoneanaerobicbloodculturebottle.Sample

threetimesadayatintervalsofseveralhours(minimumintervalone

hour).

— Forserology,(2–)5mlofnativebloodwillusuallysuffice.Taketheinitial

sampleasearlyaspossibleandasecondone 1 – 3 weekslatertoregister

anychangeintheantibodytiter.

Pusandwoundsecretions:

— Forsurfacewoundssamplematerialwithsmearswabsandtransportin

preservativetransportmediums.Suchmaterialisonlyanalyzedforaero-

bicbacteria.

— Fordeepandclosedwounds,liquidmaterial(e.g.,pus)shouldbesampled,

ifpossible,withasyringe.Usespecialtransportmediumsforanaerobes.

Materialfromthegastrointestinaltract:

— Useasmallspatulatoplaceaportionofstoolaboutthesizeofacherryin

liquidtransportmediumforshipment.

— Transportduodenaljuiceandbileinsteriletubes.Usespecialcontainers

ifanaerobesaresuspected.

Cerebrospinalfluid,puncturebiopsies,exudates,transudates:

— Ensuresamplingsterility.Usespecialcontainersifanaerobesaresus-

pected.

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Kayser, Medical Microbiology © 2005 Thieme