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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