Medical Microbiology

316 4 BacteriaasHumanPathogens

whowerevaccinatedaschildrenhavelittleornoresidualimmunityandof-

tenpresentatypicalpertussis.

Diagnosis.Thepathogencanonlybeisolatedandidentifiedduringtheca-

tarrhalandearlyparoxysmalphases.Specimenmaterialistakenfromthe

nasopharynxthroughthenoseusingaspecialswabbingtechnique.Aspecial

mediumisthencarefullyinoculatedorthespecimenistransportedtothe

laboratoryusingasuitabletransportmedium.B.pertussiscanalsobeiden-

tifiedinnasopharyngealsecretionusingthedirectimmunofluorescence

technique.Culturesmustbeaerobicallyincubatedforthreetofourdays.Anti-

bodiescannotbedetectedbyEIAuntiltwoweeksafteronsetattheearliest.

Onlyaseroconversionisconclusive.

Therapy.Antibiotictreatmentcanonlybeexpectedtobeeffectiveduringthe

catarrhalandearlyparoxysmalphasesbeforethevirulencefactorsarebound

tothecorrespondingcellreceptors.Macrolidesaretheagentsofchoice.

Epidemiologyandprevention.Pertussisoccursworldwide.Humansarethe

onlyhosts.Sourcesofinfectionareinfectedpersonsduringthecatarrhal

phase,whocoughoutthepathogensindroplets.Therearenohealthycar-

riers.

Themostimportantpreventivemeasureistheactivevaccination(seevac-

cinationschedule,p.33).Althoughawhole-cellvaccineisavailable,various

acellularvaccinesarenowpreferred.

Francisellatularensis(Tularemia)

F.tularensisbacteriaarecoccoid,nonmotile,Gram-negative,aerobicrods.

Theycauseadiseasesimilartoplagueinnumerousanimalspecies,above

allinrodents.Humansareinfectedbycontactwithdiseasedanimalsorec-

toparasitesordust.Thepathogensinvadethehosteitherthroughmicrotrau-

mataintheskinorthroughthemucosa.Anulcerouslesiondevelopsatthe

portalofentrythatalsoaffectsthelocallymphnodes(ulceroglandular,gland-

ular,oroculoglandularform).Vialymphogenousandhematogenousdissem-

inationthepathogensthenspreadtoparenchymatousorgans,inparticular

RESorganssuchasthespleenandliver.Smallgranulomasdevelop,which

developcentralcaseationorpurulentabscesses.Inpneumonictularemia,

asfewas 50 CFUcausedisease.Theincubationperiodisthreetofour

days.Diagnosticproceduresaimtoisolateandidentifythepathogenincul-

turesandunderthemicroscope.Agglutinatingantibodiescanbedetected

beginningwiththesecondweek.Aseroconversionistheconfirmingfactor.

Antibiosisiscarriedoutwithstreptomycinorgentamicin.

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Kayser, Medical Microbiology © 2005 Thieme