whooping cough.ppt

whooping cough

2. ThereareseveralspeciesofBordetella:
1-Bordetellapertussis,ahighly
communicableandimportantpathogenof
humans, causeswhooping cough
(pertussis).
2-BordetellaparapertussisItcancause
amilderpertussis-likediseaseinhumans,
butBordetellapertussisisthemost
serioushumanpathogeninthisgenus

3. The organisms are minute, gram-negative
coccobacilli
A capsule is present.
aerobic, non-spore forming,
Specific to Humans
Colonizes the respiratory tract
B.pertussisinvadesitshumanhostthrough
entryintotherespiratorytractwhereit
colonizestocausewhoopingcough,also
knownaspertussis,whichwasatonetime
averycommonandpotentiallylife
threateninginfectionforchildren

4. Pertussis is highly contagious
Pertussisisgenerallytransmittedfrom
persontopersonviarespiratorydroplets,but
directcontactwithrespiratorysecretions
frominfectedindividualsmayalsoleadtothe
disease.
90%ofnonimmunehouseholdcontactsacquire
thedisease
Adolescentsandadultsarethemajorsource
ofinfectioninunvaccinatedchildren
Infantsandyoungchildrenareinfectedby
oldersiblingswhohavemildtoasymptomatic
disease.

5. Freshlycontaminatedarticles(suchasclothing)fromthe
infectedpersoncanalsocontaininfectiousrespiratory
secretions,allowingpertussistobepassedindirectlyfromthe
infectedpersontoasusceptiblehostwhocomesindirect
contactwiththeseitems.

6. B.pertussisinvadesthehumanhostthroughtheinhalationof
respiratorydroplets adherestotheciliatedepithelium
oftherespiratorytractbutdonotinvadetheunderlyingtissue.
ItwasbelievedthatB.pertussiswasanentirelyextracellular
pathogen,butithasrecentlybeenshownthatB.pertussiscan
invadeaveolarmacrophages.
 Thispathogencanmultiplyrapidlyonthemucosal
membraneoftheupperrespiratorytract,producingadhesions
thatallowittocolonizebyadheringtotheciliatedepithelium.

7. B.pertussismustsurvivewithinthehostileenvironmentofits
humanhostbyproducingavarietyofvirulencefactorsinan
attempttoevadeorcountertheimmunesystemofthehost
asittriestocleartheinfection.
Bpertussissurvivesforonlybriefperiodsoutsidethehuman
host.Therearenovectors.
Transmissionislargelybytherespiratoryroutefromearly
casesandpossiblyviacarriers.

8. Bpertussisproducesanumberofvirulencefactorsthatare
involvedinthepathogenesisofdisease.Adhesionssuchas:
1.filamentous hemagglutinin
2.agglutinogens
3.peractin
4.fimbriae
a number of toxins including:
a.pertussis toxin
b.adenylatecyclasetoxin (ACT)
c.trachaelcytotoxin
d.dermonecrotictoxin (DNT)
e.heat-labile toxin
f.lipopolysaccharide coat that acts as an endotoxin and can aid
colonization by agglutinating human cells.

9. Filamentoushemagglutinin,alargesurfaceprotein,andfimbriae
(surfaceappendages)mediateadhesiontociliatedepithelialcells
andareessentialfortrachealcolonization.
Pertussistoxin(aclassicA/B
structuretoxin)promotes
lymphocytosis,sensitizationto
histamine,andenhancedinsulin
secretionthatdisruptsfunction
ofsignaltransductioninmanycelltypes.
Thefilamentoushemagglutininandpertussistoxinaresecreted
proteinsandarefoundoutsideoftheBpertussiscells.

10. Adenylatecyclasetoxin(ACT),
dermonecrotictoxin(DNT),and
hemolysin.ACTisanimportant
virulencefactorthatinhibits
phagocytefunctionbuttheroleof
DNTinpertussisisunknown.
Thetrachealcytotoxin kills
respiratoryepithelialcellsinvitro.
Thelipooligosaccharideinthecell
wallmayalsobeimportantincausing
damagetotheepithelialcellsof
theupperrespiratorytract.

12. Theorganismadherestoand multipliesrapidly
ontheepithelialsurfaceofthetracheaandbronchi
and interfereswithciliaryaction.The
bacteria liberatethetoxinsandsubstances
that irritatesurfacecells,causingcoughingand
markedlymphocytosis.Later, theremaybenecrosis
ofpartsoftheepitheliumandpolymorphonuclearinfiltration,
withperibronchialinflammationandinterstitialpneumonia.

15. SecondaryinvaderssuchasstaphylococciorHinfluenzaemay
giverisetobacterialpneumonia.
Obstructionofthesmallerbronchiolesbymucousplugsresults
indiminishedoxygenationoftheblood.Thisprobably
contributestothefrequencyofconvulsionsininfantswith
whoopingcough.

16. Afteranincubationperiodofabout2weeks,the
“catarrhalstage”develops,withmildcoughingandsneezing.
Duringthisstage,largenumbersoforganismsaresprayedin
droplets,andthepatientishighlyinfectiousbutnotveryill.

17. Duringthe“paroxysmal”stage,thecoughdevelopsits
explosivecharacterandthecharacteristic“whoop”upon
inhalation.Thisleadstorapidexhaustionandmaybe
associatedwithvomiting,cyanosis,andconvulsions.The
“whoop”andmajorcomplicationsoccurpredominantlyin
infants.Paroxysmalcoughingpredominatesinolderchildren
andadults.

18. Thewhitebloodcountishigh(16,000–30,000/μL),withan
absolutelymphocytosis.
Convalescenceisslow.Bpertussisisacommoncauseof
prolongedcoughinadults.
endswiththeconvalescencestageischaracterizedbyfewer
paroxysmalcoughingepisodesandusuallydisappearsin2-3
weeks,butmaycontinueformonths.
Feverminimaltoabsent.Symptomssubsidegraduallyover
months(convalescentstage1-2wks)

19. A.Specimens
Nasopharyngeal(NP)swabsorNPaspirates.
Nasal swabs are not acceptable
Foradults,coughdropletsexpelleddirectlyontoa“cough
plate”heldinfrontofthepatient’smouth,duringaparoxysm
isalessdesirablemethodofspecimencollection.

20. B.DirectFluorescentAntibodyTest
Thefluorescentantibody(FA)reagentcanbeusedtoexamine
nasopharyngealswabspecimens.However,false-positiveandfalse-
negativeresultsmayoccur;thesensitivityisabout50%.
TheFAtestismostusefulinidentifyingBpertussisafterculture
onsolidmedia.

21. C.Culture
NPaspiratesorswabsareculturedonsolid
media(Bordet-Gengoumedium)withhigh
percentageofblood(20%-30%)to
inactivateinhibitorsintheagar,andalso
containpotatoandglycerol.
Theantibioticsinthemediatendtoinhibit
otherrespiratorymicrobiotabutpermit
growthofBpertussis.
SelectivemediaforB.pertussisincludesRegan-Lowe,Bordet-
Gengou,orcharcoalagar.Successfulisolationdeclineswith
perviousexposuretoantibiotictherapyeffectiveagainst
pertussisorifspecimensarecollectedbeyondthefirsttwo
weeksofillness.Isolationisalsodifficultforvaccinated
patients.

22. D.immunofluorescencestainingorbyslideagglutinationwith
specificantiserum.
E.PolymeraseChainReaction
F. Serology
ProductionofIgA,IgG,andIgM
antibodiesoccursafterexposuretoB
pertussisandtheseantibodiescanbe
detectedbyenzymeimmunoassays.
Serologictestsonpatientsareoflittle
diagnostichelpacutelybecausearisein
agglutinatingorprecipitatingantibodies
doesnotoccuruntilthethirdweekof
illness.

23. Week
Cough Onset
1.Culture
0 2 4 6 8 10 12
PCR
Serology

24. Recoveryfromwhoopingcoughorimmunizationisfollowedby
immunitythatisnotlifelong.
Secondinfectionsmayoccurbutareusuallymilder;
reinfectionsoccurringyearslaterinadultsmaybesevere.It
isprobablethatthefirstdefenseagainstBpertussis
infectionistheantibodythatpreventsattachmentofthe
bacteriatotheciliaoftherespiratoryepithelium.
AntibodiestoPTarehighlyimmunogenic

25. Administrationoferythromycinduringthecatarrhalstageof
diseasepromoteseliminationoftheorganismsandmayhave
prophylacticvalue.
Treatmentafteronsetoftheparoxysmalphaserarelyalters
theclinicalcourse.
Oxygeninhalationandsedationmaypreventanoxicdamageto
thebrain.

26. Azithromycinisthedrugofchoice.Notethatazithromycin
reducesthenumberoforganismsinthethroatanddecreases
theriskofsecondarycomplicationsbuthaslittleeffectonthe
courseofthediseaseatthe“prolongedcough”stagebecause
thetoxinshavealreadydamagedtherespiratorymucosa.
Supportivecare(e.g.,oxygentherapyandsuctionofmucus
duringtheparoxysmalstageisimportant,especiallyininfants).

27. Therearetwotypesofvaccines:
1.anacellularvaccinecontainingpurifiedproteinsfromthe
organism.
2.akilledvaccinecontaininginactivatedB.pertussis
organisms.
Theacellularvaccinehasfewer
sideeffectsthanthekilledvaccine
buthasashorterdurationofimmunity.

28. Thepertussisvaccineisusuallygiven
combinedwithdiphtheriaandtetanustoxoids
(DTaP)inthreedosesbeginningat2months
ofage.Aboosterat12to15monthsofage
andanotheratthetimeofenteringschoolare
recommended.
Becauseoutbreaksofpertussishaveoccurred
amongteenagers,aboosterforthosebetween
10and18yearsoldisrecommended.This
vaccine,calledBoostrix,containsdiphtheria
andtetanustoxoidsalso.

29. Toprotectnewborns,pregnantwomenshouldreceivepertussis
vaccine.AntipertussisIgGwillpasstheplacentaandprotect
thenewborn.
ThekilledvaccineisnolongerusedintheUnitedStates
becauseitissuspectedofcausingvarioussideeffects,
includingpostvaccineencephalopathyatarateofaboutone
casepermilliondosesadministered.
Azithromycinisusefulinpreventionofdiseaseinexposed,
unimmunizedindividuals.Itshouldalsobegiventoimmunized
childrenyoungerthan4yearswhohavebeenexposedbecause
vaccine-inducedimmunityisnotcompletelyprotective.

30. Thisorganismmayproduceadiseasesimilartowhoopingcough,
butitisgenerallylesssevere.
Theinfectionisoftensubclinical.
BparapertussisgrowsmorerapidlythantypicalBpertussisand
produceslargercolonies.
Italsogrowsonbloodagar.
Bparapertussishasasilentcopyofthepertussistoxingene.

31. Questions?