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1、Lecture 14微生物学美国IndianaUniversityPurdueUniversity授课14Stillwatersrundeep.流静水深流静水深,人静心深人静心深Wherethereislife,thereishope。有生命必有希望。有生命必有希望Lecture 14HistoryAmerican Legion Convention in 1976 in Philadelphia hotelRespiratory distress and fever200 affected34 died BIOL 5332Lecture 14HistorySix months after o
2、utbreak, CDC isolated bacteria from post-mortum lung tissueInoculated lung tissue into peritoneal cavity of guinea pigsAfter animal became ill, removed its spleen and injected tissue into fertilized chicken eggs (rickettsial methodology)BIOL 5333Lecture 14HistoryOrganism was thought to be unique, gi
3、ven new genus and species name: Legionella pneumophilaEpidemiological search revealed outbreak in same hotel two years earlierCulture problems because organisms:Do not grow on common laboratory mediaDo not readily stainBIOL 5334Lecture 14Microbial Physiology and StructureFamily LegionellaceaeOne gen
4、us: Legionella25 species and 42 serotypesLegionella pneumophila responsible for 85% of infections (serotype 1 most common)BIOL 5335Lecture 14Microbial Physiology and StructureSpecies can be differentiated by:DNA homologyCell wall fatty acidsBiochemical testingImmunological serotypingBIOL 5336Lecture
5、 14Microbial Physiology and StructureMorphologyGram rods (pleomorphic on artificial media)Do not stain well except with special silver stainCulture: do not grow in ordinary lab media, even though they are aerobic organismsRequire high concentration of cysteine and are inhibited by sodium ions and ar
6、omatic compoundsBIOL 5337Lecture 14Microbial Physiology and StructureMedia developed have:Charcoal to absorb aromatic compoundsNon-sodium ion bufferAntibiotics to suppress other organismsDyes to make colonies visible on solid mediaBIOL 5338Lecture 14PathogenesisEncounter: aquatic; found in lakes and
7、 streamsLarge numbers in polluted water around power stationsCan live in chlorinated drinking waterNormally found in hot water tanks of buildingsGet into pipes and multiply in sediment and accumulate over period of yearsDo not spread from person to personSediment provides shelter as well as nutritio
8、n for other bacteria that can supply cysteineBIOL 5339Lecture 14PathogenesisEntry, spread, and multiplicationEntry: inhalation of organismsIncubation period: 2-10 daysInitial host response: acute inflammatory response of aveoli and then bronchioles (similar to pneumococcal infection)Neutrophils accu
9、mulate followed by macrophageBIOL 53310Lecture 14PathogenesisDifferent from pneumococcal infectionOrganisms located inside of macrophageInhibit lysosomal fusion and acidification of phagocyteBIOL 53311Lecture 14DamageOrganism possesses several exotoxinsProteases, hemolysins, and other cytotoxinsOne
10、inhibits oxidative killing of neutrophilsMay also damage tissue directlySpread rapidly in lung tissueSymptoms resulting from inflammatory disease in lungCough, chest pains, abnormal breathing sounds, and feverBIOL 53312Lecture 14DamageOther target sites: heart, kidney, lymph nodes, spleen, liver, an
11、d brainNeurological symptoms and diffuse metabolic abnormalities result from bloodstream invasion: confusion, deliriumSome patients have gastrointestinal symptoms, including diarrheaBIOL 53313Lecture 14Disease SyndromesIn general, healthy people rarely get diseaseImmunosuppressed patients and heavy
12、smokers with a history of respiratory problemsBIOL 53314Lecture 14Disease SyndromesPontiac fever (flu-like illness)Pontiac, Michigan in 1968Symptoms: fever, chills, muscle aches, malaise, headacheDevelops over 12-hour period, persists for 2-5 days, then spontaneously resolvesMinimal morbidity and no
13、 mortalityBIOL 53315Lecture 14Disease SyndromesLegionaires diseaseMuch more severe, with high mortality unless promptly treatedOverall mortality is 15-20%Symptoms reviewed in Pathogenesis sectionBIOL 53316Lecture 14EpidemiologyIncidence is poorly understood because disease documentation is difficult
14、Pneumonias due to organism: less than 1% to greater than 30%Estimated that 25,000 to 50,000 cases occur annuallyBIOL 53317Lecture 14EpidemiologyTime of yearSporadic infections throughout yearEpidemic infections occur in late summer and fallElderly with decreased pulmonary function and cellular immun
15、ity are at increased riskBIOL 53318Lecture 14Laboratory DiagnosisMicroscopyDifficult because of lack of staining intracellular natureRequire large number of organisms to detectBest test: direct fluorescent antibodyTest is very specificFalse positives observed rarely with Pseudomonas, Bacteriodes, an
16、d other organismsBIOL 53319Lecture 14Laboratory DiagnosisCulture: buffered charcoal yeast extract (BCYE)Grow after 3-5 daysAppear as small colonies with ground glass appearanceBIOL 53320Lecture 14Laboratory DiagnosisDetection of Ag in respiratory secretions or urineCan be detected immunologically or
17、 by hybridizationExcretion in urine can occur for as long as a yearBIOL 53321Lecture 14Laboratory DiagnosisSerology: indirect fluorescent antibody testFour-fold or greater increase in antibody titerResponse can be delayed as long as eight weeksBIOL 53322Lecture 14Laboratory DiagnosisIdentificationDe
18、monstration of typical morphology and growth requirementsGram bacteria (pleomorphic and weakly straining)Growth on BCYE with cysteine but no BCYEConfirmation by fluorescent antibodyBIOL 53323Lecture 14TreatmentErythromycin is antibiotic of choiceCan penetrate white blood cellsMost strains possess -l
19、actamasesBIOL 53324Lecture 14PreventionComplete elimination of organism from water supplies is almost impossibleDecrease in numbers normally effectiveNormally, healthy people not at riskHyperchlorination and heating of water frequently employedBIOL 53325Lecture 14Lecture 14Questions?Comments?Assignments.BIOL 53326
