Medical Microbiology

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