Rickettsiae | Rickettsia fever
Rickettsiae of the Spotted Fever and Typhus GroupsNCBISkiptomaincontentSkiptonavigationResourcesHowToAboutNCBIAccesskeysMyNCBISignintoNCBISignOutNCBIBookshelf.AserviceoftheNationalLibraryofMedicine,NationalInstitutesofHealth.BaronS,editor.MedicalMicrobiology.4thedition.Galveston(TX):UniversityofTexasMedicalBranchatGalveston;1996.MedicalMicrobiology.4thedition.ShowdetailsBaronS,editor.Galveston(TX):UniversityofTexasMedicalBranchatGalveston;1996.ContentsSearchtermChapter38RickettsiaeDavidH.Walker.GeneralConceptsRickettsiaeTherickettsiaeareadiversecollectionofobligatelyintracellularGram-negativebacteriafoundinticks,lice,fleas,mites,chiggers,andmammals.TheyincludethegeneraRickettsiae,Ehrlichia,Orientia,andCoxiella.Thesezoonoticpathogenscauseinfectionsthatdisseminateinthebloodtomanyorgans.RickettsiaClinicalManifestationsRickettsiaspeciescauseRockyMountainspottedfever,rickettsialpox,otherspottedfevers,epidemictyphus,andmurinetyphus.Orientia(formerlyRickettsia)tsutsugamushicausesscrubtyphus.Patientspresentwithfebrileexanthemsandvisceralinvolvement;symptomsmayincludenausea,vomiting,abdominalpain,encephalitis,hypotension,acuterenalfailure,andrespiratorydistress.Structure,Classification,andAntigenicTypesRickettsiaspeciesaresmall,Gram-negativebacillithatareobligateintracellularparasitesofeukaryoticcells.Thisgenusconsistsoftwoantigenicallydefinedgroups:spottedfevergroupandtyphusgroup,whicharerelated;scrubtyphusrickettsiaedifferinlackinglipopolysaccharide,peptidoglycan,andaslimelayer,andbelongintheseparate,althoughrelated,genusOrientia.PathogenesisRickettsiaandOrientiaspeciesaretransmittedbythebiteofinfectedticksormitesorbythefecesofinfectedliceorfleas.Fromtheportalofentryintheskin,rickettsiaespreadviathebloodstreamtoinfecttheendotheliumandsometimesthevascularsmoothmusclecells.Rickettsiaspeciesentertheirtargetcells,multiplybybinaryfissioninthecytosol,anddamageheavilyparasitizedcellsdirectly.HostDefensesT-lymphocyte-mediatedimmunemechanismsandcytokines,includinggammaint