- A family of the order Chlamydiales (formerly included in the order Rickettsiales) that includes the agents of the psittacosis-lymphogranuloma-trachoma group. The family contains small, coccoid, Gram-negative bacteria that resemble rickettsiae but that differ from them significantly by possessing a unique, obligately intracellular developmental cycle; intracytoplasmic microcolonies give rise to infectious forms by division. The classification of these organisms previously was in a state of flux, but they are now placed in a single genus, Chlamydia, the type genus of the family.
* * *Chla·myd·i·a·ce·ae klə-.mid-ē-'ā-sē-.ē n pl a family of bacteria (order Chlamydiales) that are related to members of the order Rickettsiales, that are obligate parasites in the cells of warm-blooded vertebrates, and that include the causative agents of trachoma, lymphogranuloma venereum, and psittacosis
* * *Chla·myd·i·a·ceae (klə-mid″e-aґse-e) a family of bacteria of the order Chlamydiales, consisting of small coccoid microorganisms that are incapable of synthesizing ATP and multiply only within the cytoplasm of host cells by a unique developmental cycle (see Chlamydiales). Many are parasites of vertebrates and cause diseases. They have also been found in arthropods. The family contains the genera Chlamydia and Chlamydophila.
Medical dictionary. 2011.