Chlamydias. Nonmotile, obligately parasitic, coccoid bacteria that multiply only membranebounded vacuoles in the cytoplasm of the cells of humans, other mammals,and birds. Arthropods do not serve as hosts. Multiplication occurs by means of a unique developmental cycle characterized by change of small elementary bodies into larger reticulate bodies that divide by fission. They are pathogenic. Cell walls contain no muramic acid or only a trace. Glucose is not oxidized with net generation of ATP; the parasites are dependent upon the ATP of the host cell.
The bacteria in this group require very specialized cultivation techniques for study. Only certain laboratories are equipped for their identification and, for that reason, they will not be considered further in this manual.