Taxonomy The order chlamydiales has one family, chlamydiaceae, and one genus, chlamydia. Currently four species are recognized, Chlamydia trachomatis, Chlamydia pneumoniae, Chlamydia psittaci , and Chlamydia pecorum. To date, 19 different Chlamydia trachomatis serovars (41) and several Chlamydia psittaci serovars are known (6 avian (65), 9 mammalian (29)), but only one Chlamydia pneumoniae (40,...