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.
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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
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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.