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LegionellaBIOL533Lecture14MedicalMicrobiologyBIOL5331HistoryAmericanLegionConventionin1976inPhiladelphiahotelRespiratorydistressandfever200affected34diedBIOL5332HistorySixmonthsafteroutbreak,CDCisolatedbacteriafrompost-mortumlungtissueInoculatedlungtissueintoperitonealcavityofguineapigsAfteranimalbecameill,removeditsspleenandinjectedtissueintofertilizedchickeneggs(rickettsialmethodology)BIOL5333HistoryOrganismwasthoughttobeunique,givennewgenusandspeciesname: LegionellapneumophilaEpidemiologicalsearchrevealedoutbreakinsamehoteltwoyearsearlierCultureproblemsbecauseorganisms:DonotgrowoncommonlaboratorymediaDonotreadilystainBIOL5334MicrobialPhysiology

andStructureSpeciescanbedifferentiatedby:DNAhomologyCellwallfattyacidsBiochemicaltestingImmunologicalserotypingBIOL5336MicrobialPhysiology

andStructureMorphologyGram—rods(pleomorphiconartificialmedia)DonotstainwellexceptwithspecialsilverstainCulture:donotgrowinordinarylabmedia,eventhoughtheyareaerobicorganismsRequirehighconcentrationofcysteineandareinhibitedbysodiumionsandaromaticcompoundsBIOL5337MicrobialPhysiology

andStructureMediadevelopedhave:CharcoaltoabsorbaromaticcompoundsNon-sodiumionbufferAntibioticstosuppressotherorganismsDyestomakecoloniesvisibleonsolidmediaBIOL5338PathogenesisEncounter:aquatic;foundinlakesandstreamsLargenumbersinpollutedwateraroundpowerstationsCanliveinchlorinateddrinkingwaterNormallyfoundinhotwatertanksofbuildingsGetintopipesandmultiplyinsedimentandaccumulateoverperiodofyearsDonotspreadfrompersontopersonSedimentprovidesshelteraswellasnutritionforotherbacteriathatcansupplycysteineBIOL5339PathogenesisEntry,spread,andmultiplicationEntry:inhalationoforganismsIncubationperiod:2-10daysInitialhostresponse:acuteinflammatoryresponseofaveoliandthenbronchioles(similartopneumococcalinfection)NeutrophilsaccumulatefollowedbymacrophageBIOL53310PathogenesisDifferentfrompneumococcalinfectionOrganismslocatedinsideofmacrophageInhibitlysosomalfusionandacidificationofphagocyteBIOL53311DamageOrganismpossessesseveralexotoxinsProteases,hemolysins,andothercytotoxinsOneinhibitsoxidativekillingofneutrophilsMayalsodamagetissuedirectlySpreadrapidlyinlungtissueSymptomsresultingfrominflammatorydiseaseinlungCough,chestpains,abnormalbreathingsounds,andfeverBIOL53312DamageOthertargetsites:heart,kidney,lymphnodes,spleen,liver,andbrainNeurologicalsymptomsanddiffusemetabolicabnormalitiesresultfrombloodstreaminvasion:confusion,deliriumSomepatientshavegastrointestinalsymptoms,includingdiarrheaBIOL53313DiseaseSyndromesIngeneral,healthypeoplerarelygetdiseaseImmunosuppressedpatientsandheavysmokerswithahistoryofrespiratoryproblemsBIOL53314DiseaseSyndromesPontiacfever(flu-likeillness)Pontiac,Michiganin1968Symptoms:fever,chills,muscleaches,malaise,headacheDevelopsover12-hourperiod,persistsfor2-5days,thenspontaneouslyresolvesMinimalmorbidityandnomortalityBIOL53315DiseaseSyndromesLegionaire’sdiseaseMuchmoresevere,withhighmortalityunlesspromptlytreatedOverallmortalityis15-20%SymptomsreviewedinPathogenesissectionBIOL53316EpidemiologyIncidenceispoorlyunderstoodbecausediseasedocumentationisdifficultPneumoniasduetoorganism:lessthan1%togreaterthan30%Estimatedthat25,000to50,000casesoccurannuallyBIOL53317EpidemiologyTimeofyearSporadicinfectionsthroughoutyearEpidemicinfectionsoccurinlatesummerandfallElderlywithdecreasedpulmonaryfunctionandcellularimmunityareatincreasedriskBIOL53318LaboratoryDiagnosisMicroscopyDifficultbecauseoflackofstainingintracellularnatureRequirelargenumberoforganismstodetectBesttest:directfluorescentantibodyTestisveryspecificFalsepositivesobservedrarelywithPseudomonas,Bacteriodes,andotherorganismsBIOL53319LaboratoryDiagnosisCulture:bufferedcharcoalyeastextract(BCYE)Growafter3-5daysAppearassmallcolonieswithgroundglassappearanceBIOL53320LaboratoryDiagnosisDetectionofAginrespiratorysecretionsorurineCanbedetectedimmunologicallyorbyhybridizationExcretioninurinecanoccurforaslongasayearBIOL53321LaboratoryDiagnosisSerology:indirectfluorescentantibodytestFour-foldorgreaterincreaseinantibodytiterResponsecanbedelayedaslongaseightweeksBIOL53322LaboratoryDiagnosisIdentificationDemonstrationoftypicalmorphologyandgrowthrequirementsGram—bacteria(pleomorphicandweaklystraining)GrowthonBCYEwithcysteinebutnoBCYEConfirmationbyfluorescentantibodyBIOL53323TreatmentErythromycinisantibioticofchoiceCanpenetratewhitebloodcellsMoststrainspossess-lactamasesBIOL53324PreventionCompleteel

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