Medical Microbiology

Borrelia(RelapsingFever,LymeDisease) 325

Borreliaecanbeculturedusingspecialnutrientmediums,althoughit

mustbeaddedthatnegativeresultsarenotreliable.

Pathogenesisandclinicalpicture.B.recurrentisispathogeniconlyinhu-

mans.Thepathogensaretransmittedbybodylice.B.duttonii,B.hermsii,

andotherspeciesaretransmittedbyticks.

Followinganincubationperiodoffivetoeightdays,thediseasemanifests

withfeverthatlaststhreetosevendays,thensuddenlyfalls.Anumberof

feverfreeintervals,eachlongerthanthelast,areinterruptedbyrelapses

thatarelessandlesssevere.Theborreliaecanbedetectedinthepatient’s

bloodduringthefebrileepisodes.Thediseasegotitsnamefromtheserecur-

ringfebrileattacks.Therelapsesarecausedbyborreliaethathavechanged

theirantigenstructureinsuchawaythattheantibodiesproducedinre-

sponsetothelastproliferativeepisodecannotattackthemeffectively.Bor-

reliaepossessahighlyvariablegenecodingfortheadhesionproteinVMP

(variablemajorprotein)intheoutermembraneofthecellwall.

Diagnosis.Borreliaecanbedetectedinpatients’bloodwhenthefeverrises.

Theycannotbereliablycultured.Onemethodistoinjectpatientbloodi.p.

intomice.Aftertwotothreedays,themousedevelopsabacteremiathat

canbeverifiedbyfindingthepathogensinitsbloodunderamicroscope.

Therapy.TheantibioticofchoiceispenicillinG.Alternativesincludeother

betalactamantibioticsanddoxycycline.

Epidemiologyandprevention.B.recurrentiscausestheepidemicformof

relapsingfever,whichstilloccurredworldwideatthebeginningofthe

20 thcenturybuthasdisappearedforthemostparttoday.Thepathogens

Borreliaduttonii

Fig.4. 24 Preparation from the

bloodofanexperimentallyinfected

mouse.Giemsastaining.

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Kayser, Medical Microbiology © 2005 Thieme