《病原生物学（医学微生物学）》课程教学课件（英文）06_Bacteria Pathogenesis

Section III BacteriologyPathogenesis of Bacterial InfectionSHIHEZI UNIVERSITY

Section III Bacteriology Pathogenesis of Bacterial Infection SHIHEZI UNIVERSITY

KEY TERMS PathogenExtra/intracellular pathogenCompromised hostOpportunistic infection InfectionExotoxinEndotoxin Infectious diseases Koch's postulatesAutoimmunity TransmissionBioterrorismAdhesion PenetrationInvasiveness/spreadSHIHEZI UNIVERSITY

KEY TERMS  Pathogen  Opportunistic infection  Infection  Infectious diseases  Koch’s postulates  Transmission  Adhesion  Penetration  Invasiveness/spread  Extra/intracellular pathogen  Compromised host  Exotoxin  Endotoxin  Autoimmunity  Bioterrorism SHIHEZI UNIVERSITY

GLOSSARYAeasonaachmnhossInvaoThposswheyacteriaanmaparasitewhichbacteriasticktothesurfacesofhostcells.Oncefugindirustispin the bodybacriahntthymNonpathogenAmicroorganismthatdoesnotcausedisinitialstepintheinfectionprocess.Thetermsadherease:maybepartofthenormalfloraenceadsonandatachmntarftenusedintchangeably.OpportunisticpathogenAnagentcapableofcausinCarrierAeronoranmalwithasymptomaticinfectiodiseaseonlywhenthehost'sresistanceisimpaired(iewhenthepatientis"mmunocompromised")thatcanbetransmittedtoanothersusceptiblepersonPathgenmicoorganmapablecaungdiseasor animal.InfectionMultiplicatiofaninfectiousagentwithinthePathogenicityTheabilityofaninfectiousagenttocausepody.Multiplicationfthebacteriathatarepartfthdisease seealso virulenceToxigenicityTheabilityfamicroorganismproduceamahtrsakerallynotconsideredaninfectionontheotherhandtoxinthatcontributestothedevelopmentofdiseaseViruunttiltaumultplicatioanbriaamaspecies)evenifthepersonisasymptomaticsdisease.Virulentagentscausedisease when introduceddeemed an infection.intothehostinsmallnumbers.Virulenceinvolvesinvasionand toxigenicity (see above)SHIHEZI UNIVERSITY

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Pathogen Definition: a microorganism capable ofcausing diseaseCharacteristicsTransmissibility Adherence to host cellsInvasion of host cells and tissuesToxigenicityAbility to evade the host's immune systemSHIHEZI UNIVERSITY

Pathogen  Definition: a microorganism capable of causing disease  Characteristics Transmissibility Adherence to host cells Invasion of host cells and tissues Toxigenicity Ability to evade the host’s immune system SHIHEZI UNIVERSITY

Identifying Bacteria That CauseDisease:Koch's postulates Isolateddiseased not healthy peoplePostulale 1The sutpectad penogirnipaninshauldtencasdlftetoard ataerthon ecthnGrowthmnddbiod on pure culture39Postulate2hesusoecdona8gmetashoaid be ponimpreueolthyanindsuspec Induce diseasepithognosalehealhatBsuspendpatogerPostulate3Calb tomapuectechtesedogait susceptible animalsshold caisedehaty armeoetentbymosep Re-isolatedPestulate 4The opaniomshoud bedudstonibeteseasteF susceptible animalsPurealnesoidsfpatrognasbesameogerisnas beteSHIHEZI UNIVERSITY

Identifying Bacteria That Cause Disease: Koch's postulates  Isolated diseased not healthy people  Growth pure culture  Induce disease susceptible animals  Re-isolated susceptible animals SHIHEZI UNIVERSITY

HealthyDiseasedanimalanimalPostulate1The suspected pathogenicObserveRedorganismshouldbepresentblood/issuebloodinall casesofthediseaseunderthecelland absentfrom healthymicroscopeanimas.SuspectedRed blood cellpathogenSHIHEZI UNIVERSITY

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No organismspresentStreak agar platePostulate2with sampleThe suspectedorganismfrom eithershould be grownin purediseased orculture.healthy animalColoniesof suspectedpathogenInoculate healthyanimal withcellsof suspected pathogenSHIHEZI UNIVERSITY

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Inoculate heathyanimal with ellsof suspected pathogenPostulate 3Cells froma pure cutureofthesuspectedorganismshouldcausediseaseinahealthy animal.DiseasedanimalRemove blood ortisue sample andobserve by microscopySHIHEZI UNIVERSITY

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Remove blood ortissue sample andobserve by microscopyPostulate 4LaboratoryThe organism should beculturereisolatedand shownto bethe same as theorginal.0Q080Pure cuureSuspected pathogen(must besameorganismas before)SHIHEZI UNIVERSITY

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Table9GuidelinesforestablishingthecausesofinfectiousdiseasesMolecular Koch'sPostulatesKoch's Postulates1. The microorganism1. The phenotype or prop-should be found in allerty underinvestigationcases of the disease inshould be significantyquestion,and its distri-associated with patho-bution in the bodygenic trains ofa speciesshould be in accordanceand not with nonpatho-with the lesionsgenic trains.observed.2. The microorganism2. Specificinactvation ofshould be grown in purethe gene or genesasso-culture in vitro (or outsideciated with the sus-the body of the host) forpected virulence tritseveral generations.should lead to ameasurable decrease inpathogenicity orvirulence.3. When such a pure cul-3. Reversion or replaceture isinoculated intoment ofthe mutatedsusceptible animalgene with the wild-typespecies the typical dis-gene should lead torestoration of patho-ease must result.genicity or virulence.4. The microorganism mustagain be isolated fromthe lesions of suchexperimentaly produceddisease.SHIHEZIUNIVERSITY

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