The
Chlamydiaceae are a family of bacteria that belongs to the phylum
Chlamydiae, order
Chlamydiales. All Chlamydiaceae species are Gram-negative and express the family-specific lipopolysaccharide
epitope αKdo-(2→8)-αKdo-(2→4)-αKdo (previously called the genus-specific epitope). Chlamydiaceae
ribosomal RNA genes all have at least 90%
DNA sequence identity. Chlamydiaceae species have varying inclusion morphology, varying extrachromosomal
plasmid content, and varying sulfadiazine resistance.