Medical Microbiology

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DNAViruses 423

Cytomegalovirus(CMV)
Pathogen,pathogenesis,clinicalpicture.CMVischaracterizedbyanarrow
spectrumofhosts,slowreplication,frequentlyinvolvingformationofgiant
cellsandlate,slowdevelopmentofcytopathology.
Aninitialinfectionwithcytomegalyisinapparentinmostpersons,evenin
veryearly—perinatalorpostnatal—infections.Thevirusapparentlypersistsin
thelatentstateinmononuclearcells.Reactivationcanalsorunanasympto-
maticcourse,butsymptomsmayalsodevelopthataregenerallyrelatively
mild,suchamononucleosislikeclinicalpictures,mildformsofhepatitisor
otherfebrileillnesses.Dropletinfectionisthemostfrequentrouteoftrans-
mission,butsmearinfectionsandnursinginfectionsarealsopossible.Gen-
eralizedcontaminationwiththispathogen(over 90 %oftheadultpopulation
isinfected),frequentreactivationwith,insomecases,monthsofcontinued
excretionofvirusesinsalivaandurineandthewidevarietyofpotentialclin-
icalpicturesareallfactorsthatoftenmakeitdifficulttoimplicateCMVasthe
etiologicalcauseofanobservedillness.Thevirusinfectioncanmanifestasa
sequelinsteadofacause,forinstanceofaflulikeillness.Tolaborthepoint
somewhat,itcouldbesaidthatthepatientisnotprimarilyillduetoaCMV
infection,butratherhasafloridCMVinfectionbecauseheorsheisill.
ThesituationisdifferentinAIDS,transplantationormalignancypatients,
inwhomafreshCMVinfectionorreactivation—similarlytoHSVandVZV—
canresultinseveregeneralizedinfectionswithlethaloutcome.Theliverand
lungsarethemainorgansinvolved.RetinitisisalsofrequentinAIDSpatients.
Inkidneytransplantpatients,aCMVinfectionofthemesangialcellscanre-
sultinrejectionofthetransplant.AnotherfearedCMV-causedconditionisan
intrauterinefetalinfection,whichalmostalwaysresultsfromaprimaryin-
fectioninthemother:in 10 %ofcasestheinfectionresultsinseveredefor-
mities.
Diagnosis.Amplificationcultures(p.408f.)fromsaliva,urine,buffycoat,
tissue,orBAL(bronchoalveolarlavage)areasuitablemethodofconfirming
afloridCMVinfection.Intransplantationpatients,theriskofaCMVmani-
festationcanbeestimatedbyimmunocytochemicalmonitoringoftheCMV-
positivecellcountintheperipheralblood(“antigenemiatest”),sincethis
countnormallyrisesseveraldaysbeforeclinicalmanifestationsappear.Based
onsuchanearlywarning,antiviraltherapycanbestartedintime(ganciclovir,
foscarnet).PCRresultsmustbeinterpretedwithaclearideaofhowsensitive
themethodusedcanbe,sincethenumbersofvirusesfoundmaybeclinically
insignificant.Hastyconclusionscanresultin“overdiagnosis,”aboveallin
CMV-positivetransplantrecipients.
Serologicalresultsarehardlyusefulinclarifyingafloridinfectiondueto
thehighlevelofgeneralizedcontamination.Addedtothisisthefactthat
theimmunoincompetentpatientsinwhomdiagnosisofthisinfectionwould

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Kayser, Medical Microbiology © 2005 Thieme

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