Chlamydiaceae Infections: Infections with bacteria of the family CHLAMYDIACEAE.Chlamydiaceae: A family of gram-negative, coccoid microorganisms, in the order CHLAMYDIALES, pathogenic for vertebrates. Genera include CHLAMYDIA and CHLAMYDOPHILA.Chlamydiales: An order of obligately intracellular, gram-negative bacteria that have the chlamydia-like developmental cycle of replication. This is a two-stage cycle that includes a metabolically inactive infectious form, and a vegetative form that replicates by binary fission. Members of Chlamydiales are disseminated by aerosol or by contact. There are at least six recognized families: CHLAMYDIACEAE, Criblamydiaceae, Parachlamydiaceae, Rhabdochlamydia, Simkaniaceae, and Waddliaceae.Chlamydia: A genus of the family CHLAMYDIACEAE whose species cause a variety of diseases in vertebrates including humans, mice, and swine. Chlamydia species are gram-negative and produce glycogen. The type species is CHLAMYDIA TRACHOMATIS.Chlamydophila: A genus of the family CHLAMYDIACEAE comprising gram-negative non CHLAMYDIA TRACHOMATIS-like species infecting vertebrates. Chlamydophila do not produce detectable quantities of glycogen. The type species is CHLAMYDOPHILA PSITTACI.