Medical Microbiology

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Brucella,Bordetella,Francisella 315

Bordetella(WhoopingCough,Pertussis)


ThegenusBordetella,amongothers,includesthespeciesB.pertussis,B.para-
pertussis,andB.bronchiseptica.Ofthethree,thepathogenresponsiblefor
whoopingcough,B.pertussis,isofgreatestconcernforhumans.Theother
twospeciesareoccasionallyobservedashumanpathogensinlowerrespira-
torytractinfections.
Morphologyandculture.B.pertussisbacteriaaresmall,coccoid,nonmotile,
Gram-negativerodsthatcanbegrownaerobicallyonspecialcultureme-
diumsat 378 Cforthreetofourdays.
Pathogenesis.Pertussisbacteriaaretransmittedbyaerosoldroplets.They
areabletoattachthemselvestothecellsoftheciliatedepitheliuminthe
bronchi.Theyrarelyinvadetheepithelium.Theinfectionresultsin(sub-)
epithelialinflammationsandnecroses.

PathogenicityFactorsofBordetellapertussis
&Adhesionfactors.Thetwomostimportantfactorsarefilamentoushemagglu-
tin(FHA)andpertussistoxin(Ptx).Thelattercanfunctionbothasanexotoxinandas
anadhesin.Thepathogeniccellsattachthemselvestotheepithelialcilia.
&Exotoxins.Pertussistoxin:ABtoxin(seep. 1 6);theAcomponentisanADP-ri-
bosyltransferase;mechanismofactionviaGsproteins(aswithcholeratoxinA1);
increasedamountofcAMPintargetcells,withavarietyofeffectsdependingonthe
typeofcellaffectedbythetoxin.
Invasiveadenylatecyclase:ABtoxin;Aenterscells,actsinadditiontopertussistoxin
toincreaselevelsofcAMP.
&Endotoxins.Trachealcytotoxin:mureinfragment;killsciliatedepithelialcells.
Lipopolysaccharide:stimulatescytokineproduction;activatescomplementby
thealternativepathway.

Clinicalpicture.Theonsetofwhoopingcough(pertussis)developsafteran
incubationperiodofabout 10 – 14 dayswithanuncharacteristiccatarrhal
phaselasting 1 – 2 weeks,followedbythetwotothreeweek-longparoxysmal
phasewithtypicalconvulsivecoughingspells.Thencomestheconvalescent
phase,whichcanlastforseveralweeks.Frequentcomplications,especiallyin
infants,includesecondarypneumoniascausedbypneumococciorHaemo-
philus,whichareabletopenetratereadilythroughthedamagedmucosa,
andotitismedia.Encephalopathydevelopsasadelayedcomplicationina
smallnumberofcases(0.4%),wherebythepathomechanismhasnotyet
beenclarified.Thelethalitylevelforpertussisduringthefirstyearoflife
isapproximately 1 – 2 %.Theinfectionconfersastableimmunity.Adults

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Kayser, Medical Microbiology © 2005 Thieme

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