兽医专业英语（扬州大学）lesson fou

LessonFourteenBrucellaSpecies精选pptNewwordsandphrasesBrucellaCoccobacillaryCoccobacilliDecolouriseZiehl-NeelsenstainCarbolfuchsinAerobicCapnophilicCatalaseOxidaseB.ovisSuppurationCaseationPredilectionAllantoicErythritolSteroidHormonePlacentaeUndulantPyrexiaMalaisefatigueOsteomyelitisUreaseMacConkeyB.

abortusbiotype2VenerealUterusConjunctivaInhalationEndotoxinThoracicductParenchymatous精选pptTextBrucellaspeciesaresmallGram-negativerods(0.5~0.7μm×0.6~1.5μm)thatoftenappearcoccobacillary.Theyarenon-motile,non-sporeformingandpartiallyacid-fastinthattheyarenotdecolourisedby0.5percentaceticacid(乙酸)inthemodifiedZiehl-Neelsen(MZN)stain.Thecarbolfuchsinisretainedandthebrucellaeappearasred-stainingcoccobacilli.精选pptThebrucellaeareaerobicandcapnophilic,catalase-positive,oxidase-positive(exceptB.

ovisandB.neotomae),urease-positive(exceptB.

ovis)andwillnotgrowonMacConkeyagar.B.ovisandB.abortusbiotype2requiremediaenrichedwithbloodorserum.Thegrowthofotherbrucellaeisenhancedonenrichedmediabuttheyareabletogrowonnutrientagar.精选pptBrucellaspeciesareobligateparasitesandeachspecieshasapreferrednaturalhostthatservesasareservoirofinfection.Brucellaehaveapredilectionforungulate(有蹄动物的)placentas,foetalfluidsandtestes(睾丸)ofbulls,rams,boarsanddogs.B.abortusisexcretedinbovinemilkandcanremainviableinmilk,wateranddampsoilforupto4months.精选pptTransmissionisbydirectorindirectcontactwithinfectiveexcretors（排菌者）.TherouteofinfectionisoftenbyingestionbutvenerealtransmissionmayoccurandisthemainrouteforB.ovis.Thebrucellaepossessanendotoxinthatcontributestothepathogenesis,asdoesasurfacecellwallcarbohydratethatisresponsibleforbindingtoB-lymphocytes.精选pptSoonafterentryintothehostthebrucellaeareengulfedbyphagocyticcellsinwhichtheysurvive,multiplyandaretransportedtotheregionallymphnodes.Theorganismspasstothethoracicductandthenviatheblood-streamtoparenchymatous(实质的)organsandothertissuessuchasjoints.Granulomatous(肉芽肿)focicandevelopintissuewithoccasionalsuppurationandcaseation.精选pptBrucellosisisessentiallyadiseaseofthesexuallymatureanimal,thepredilectionsitesbeingthereproductivetractsofmalesandfemales,especiallythepregnantuterus.Allantoicfactorsstimulatethegrowthofmostbrucellae.Thesefactorsincludeerythritol,possiblysteroidhormonesandothersubstances.Erythritolispresentintheplacentaandmalegenitaltractofcattle,sheep,goatsandpigsbutnothumans.ErythritoldoesnotstimulatethegrowthofB.ovisandinhibitsB.abortusstrain19,theattenuatedvaccinalstrain.精选pptApyogranulomatousreactionoccursinaffectedplacentaeandabortionoccursfrommid-gestationonwards.Apparentlynormal,butinfectedneonatescanbebornbuttheinfectionisoflimiteddurationintheseanimals.Femalesusuallyabortonlyonce,afterwhichadegreeofimmunitydevelops,andtheanimalsremaininfectedandlargenumbersofbrucellaecanbeexcretedinfoetalfluidsatsubsequentparturitions.PermanentinfertilitymayoccurinmaledogsinfectedwithB.canis.精选pptHumanscanbeinfectedbyalltheBrucellaspecies,exceptB.ovisandthenon-pathogenicB.neotomae,anddevelopundulantfever.Themanifestationsareanundulatingpyrexia,malaise,fatigue,nightsweats,muscleandjointpains,butnotabortion.Osteomyelitisisthemostcommoncomplication.HumanscanalsodevelopahypersensitivitytotheantigensofbothvirulentB.abortus

andthevaccinalstrain19.精选pptThemycobacteriaarethinrodsofvaryinglengthsandsometimesbranchingfilamentousformsoccurbuttheseeasilyfragmentintorods.Inpreviouslyunexposedanimals,localmultiplicationofthemycobacteriaoccursandtheresistancetophagocytickillingallowscontinu