Medical Microbiology

328 4 BacteriaasHumanPathogens

malsfromrodentsonuptodeerarethenaturalreservoiroftheLymedisease

Borrelia,althoughthesespeciesseldomcomedownwiththedisease.The

ticksobtaintheirbloodmealsfromtheseanimals.

Leptospira(Leptospirosis,WeilDisease)

&ThepathogenicspeciesLeptospirainterrogansissubclassifiedinover 100

serovarsreflectingdifferentsurfaceantigens.Theserovarsaredividedinto 19

serogroups(icterohemorrhagiae,canicola,pomona,etc.).Theseorganismsare

intheformofspiralrodsandcanbegrowninin-vitrocultures.Leptospirosis

isazoonosisthatoccursworldwide.Thesolesourcesofinfectionarediseased

rodentsanddomesticanimals(pigs),whichexcretethepathogenintheirur-

ine.Uponcontact,leptospiraepenetrateskinormucosa,aredisseminated

hematogenouslyandcauseageneralizedvasculitisinvariousorgans.Thein-

cubationperiodissevento 12 days.Thediseaseatfirstpresentsasasepsis,

followedafterthreetosevendaysbytheso-calledimmunestage.Inthe

milderform,anictericleptospirosis,themostfrequentmanifestationinstage

twoisanasepticmeningitis.Theictericformofleptospirosis(Weildisease)

cancausedysfunctionofliverandkidneys,cardiovasculardisruptions,and

hemorrhages.Themethodofchoiceinlaboratorydiagnosticsisantibody

identificationinalysis-agglutinationreaction.Thetherapeuticagentof

choiceispenicillinG. &

Classification.LeptospiraebelongtothefamilyLeptospiraceae.Thegenus

Leptospiracomprisestwospecies.L.biflexaincludesallapathogenicleptos-

piraeandL.interrogansrepresentsthepathogenicspecies.Basedonitsspe-

cificsurfaceantigenvariety,L.interrogansissubclassifiedinover 100 serovars

in 19 serogroups.Someofthemostimportantserogroupsare:icterohemor-

rhagiae,canicola,pomona,australis,grippotyphosa,hyos,andsejroe.

Morphologyandculture.Leptospiraearefinespirochetes, 10 – 20 lmlong,

and0. 1 – 0.2lmthick(Fig.4. 26 ).Theypossessnoflagella,butratherderive

theirmotilityfromrotatingmotionsofthecellcorpus.Visualizationoflep-

tospiraeisbestdoneusingdarkfieldorphasecontrastmicroscopy.Lepto-

spiraecanbegrowninspecialculturemediumsunderaerobicconditions

attemperaturesbetween 27 – 308 C

Pathogenesisandclinicalpicture.Leptospiraeinvadethehumanorganism

throughmicroinjuriesintheskinortheintactconjunctivalmucosa.Thereare

nosignsofinflammationinevidenceattheportalofentry.Theorganisms

spreadtoallpartsofthebody,includingthecentralnervoussystem,hema-

togenously.Leptospirosisisactuallyageneralizedvasculitis.Thepathogens

4

Kayser, Medical Microbiology © 2005 Thieme