Medical Microbiology

416 8 VirusesasHumanPathogen

withinoneyear.TheBKviruscancausehemorrhagiccystitisinbonemarrow

transplantationpatients.

Diagnosis.TheJCandBKvirusescanbegrownincultures,albeitwithgreat

difficultyandnotfordiagnosticpurposes.BothcanbedetectedwithPCRand

theBKviruscanbeseenundertheelectronmicroscopeinurine.Antibody

assaysarepracticallyuselessduetothehighlevelofgeneralizedcontamina-

tion.

Epidemiology.Despitethehighlevelofgeneralizedcontamination,thetrans-

missionroutesusedbythehumanpolyomaviruseshavenotbeenclarified.

Adenoviruses

&Thereareatotalof 41 typesofadenovirusesandtheycauseawidevariety

ofdiseases.Influenzainfectionsoftheupper,lessfrequentlythelower,

respiratorytractandeyeinfections(follicularconjunctivitis,keratoconjunc-

tivitis)areamongthemoresignificantclinicalpictures.Intestinalinfections

aremainlycausedbytheonlynotculturablevirustypes 40 and 41 .Diagnosis:

antibodyassayinrespiratoryadenovirusinfections.Serologyisnotreliablein

theeyeandintestinalinfections.Itispossibletoisolatethepathogensincell

culturesfromeyeinfections.Enteraladenovirusesaredetectedinstoolby

meansofelectronmicroscopy,enzymeimmunoassay,orpassiveagglutina-

tion. &

Pathogens.Adenovirusesarenonenveloped, 70 – 90 nminsize,andicosahe-

dral.Theirmorphogenesisoccursinthecellnucleus,wheretheyalsoaggre-

gatetoformlargecrystals(Fig.8. 3 ).Theirgenomeisalinear, 36 – 38 kbpdou-

ble-strandedDNA.Adenovirusesgottheirnamefromtheadenoidaltissues

(tonsils)inwhichtheywerefirstidentified.

Pathogenesisandclinicalpicture.Adenovirusescauseavarietyofdiseases,

whichmayoccursinglyorconcurrently.Themostimportantareinfectionsof

theupper(sometimeslower)respiratorytracts,theeyes,andtheintestinal

tract.

&Infectionsoftherespiratorytracttaketheformofrhinitisorabacterial

pharyngitis,dependingonthevirustypeaswellaspresumablyonthedis-

positionofthepatient.Theymayalsodevelopintoacute,influenzalikeinfec-

tionsoreven,especiallyinsmallchildren,intoapotentiallyfatalpneumonia.

&Theeyeinfections,whichmayoccuralonebutareoftenconcurrentwith

pharyngitis,rangefromfollicularconjunctivitistoaformofkeratoconjunc-

tivitisthatmayevencausepermanentpartiallossofeyesight.

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Kayser, Medical Microbiology © 2005 Thieme