Medical Microbiology

LaboratoryDiagnosis 207

withmeningococcicarriers,beforesurgeryinvolvingmassivebacterialcon-

tamination,inheavilyimmunocompromisedpatients,incardiacsurgeryorin

femoralamputationsduetocirculatoryproblems.Chemoprophylaxisaimed

atpreventingapostsurgicalinfectionshouldbeginafewhoursbeforethe

operationandneverbecontinuedforlongerthan 24 – 72 hours.

Immunomodulators.......................................

Despitethegenerallygoodefficacyofanti-infectiveagents,therapeuticsuc-

cesscannotbeguaranteed.Completeeliminationofbacterialpathogensalso

requiresafunctioningimmunedefensesystem.Inviewofthefactthatthe

numberofpatientswithsevereimmunodeficienciesisontherise,immuno-

modulatorsareusedasasupportiveadjuncttospecificantibiotictherapyin

suchpatients.Manyofthese“cytokines”(seep.77ff.)producedbythecellsof

theimmunesystemcannowbeproducedas“recombinantproteins.”Mye-

lopoieticgrowthfactorshavenowbeensuccessfullyusedinpatientssuffer-

ingfromneutropenia.Additionalimmunomodulatorsarealsoavailable,e.g.,

interferongamma(IFNc)andinterleukin 2 (IL-2).

LaboratoryDiagnosis..............................................

&Infectionscanbediagnosedeitherdirectlybydetectionofthepathogenor

componentsthereoforindirectlybyantibodydetectionmethods.Thereli-

abilityoflaboratoryresultsischaracterizedbythetermssensitivityandspec-

ificity,theirvalueismeasuredintermsofpositivetonegativepredictive

value.Thesepredictivevaluesdependtoagreatextentonprevalence.Indi-

rectlaboratorydiagnosis,correctmaterialsamplingandadequatetransport

precautionsareanabsolutenecessity.Theclassicmethodsofdirectlabora-

torydiagnosisincludemicroscopyandculturing.Identificationofpathogens

is based onmorphological, physiological, andchemical characteristics.

Amongthelatter,theimportanceofdetectionofpathogen-specificnu-

cleotidesequencesisconstantlyincreasing.Developmentofsensitive

testsystemshasmadedirectdetectionofpathogencomponentsintestma-

terialspossibleinsomecases.Themolecularbiologicalmethodsusedareap-

pliedwithorwithoutamplificationofthesequencesoughtasthecasewar-

rants.Directdetectioncanalsoemploypolyclonalormonoclonalantibodies

todetectandidentifyantigens. &

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Kayser, Medical Microbiology © 2005 Thieme