ExpandallsectionsRegister/LoginTrustedmedicalexpertiseinseconds.Access1,000+clinicalandpreclinicalarticles.Findanswersfastwiththehigh-poweredsearchfeatureandclinicaltools.Tryfreefor5daysEvidence-basedcontent,createdandpeer-reviewedbyphysicians.Readthedisclaimer.ChlamydiainfectionsLastupdated:February9,2021SummaryChlamydiaceaeisafamilyofgram-negative,obligateintracellularbacteriathatincludes3organismspathogenictohumans:Chlamydiatrachomatis,Chlamydophilapneumoniae,andChlamydophilapsittaci.C.trachomatiscanbedifferentiatedintoserotypesA–C,D–K,andL1–L3.SerotypesA–Cmainlyaffecttheeyesandcausetrachoma.AninfectionwithserotypesD–Kcanresultingenitourinaryinfections(e.g.,vaginitis,PID,urethritis),conjunctivitis,andinfantpneumonia.SerotypesL1–L3,inturn,leadtosexuallytransmittedlymphogranulomavenereum.WhilebothC.pneumoniaeandC.psittaciprimarilyaffecttherespiratorysystem,C.psittacialsocausespsittacosis.Chlamydialinfectionsaremostlydiagnosedbasedonclinicalpresentationandaretreatedwithdoxycyclineormacrolides.Inallcasesofsexuallytransmittedchlamydialinfection,expeditedpartnertherapyshouldalsobeinitiatedassoonaspossible.Allocularmanifestationsarediscussedinmoredetailinthe“Conjunctivitis”article.GeneralGeneralcharacteristicsGram-negativeorganisms,thatGramstainpoorlyObligateintracellularbacteria(unabletoproduceitsownATP)Absentpeptidoglycan(muramicacid)inthecellwall,whichmakesbeta-lactamantibioticsineffectiveVisibleascytoplasmicinclusionbodiesonGiemsastainorfluorescentantibody-stainedsmearVerydifficultcultivationLifecycleFirstphase:elementarybodies(smallanddensebodiesthatcharacterizetheinfectiousstageofChlamydiaceae;stableintheextracellularenvironmentandalmostinactivemetabolically)[1]Attachmentofextracellularelementarybodiestotargetcells(mostlyontherespiratoryorurogenitalepithelium)EndocytosisTransformationintoreticulatebodiesintheendosomeSecondphase:reticulatebodies(representtheobligateintracellular,replicative,andmetabolicallyactiveformofChlamydiaceae)Replicationbyfissionandaggregatio