Ultrastructural analysis of the effect of trimethoprim and sulphamethoxazole on the development of Chlamydia trachomatis in cell culture.

Folic acid antagonists have been demonstrated to cause gross changes in the morphology of chlamydial inclusions in cell culture. The ultrastructural changes were examined by electron microscopy in cultures of Chlamydia trachomatis treated with trimethoprim and sulphamethoxazole. Examination of these cultures demonstrated a failure of the reticulate bodies to develop into normal elementary bodies. These changes were seen in cultures treated with either compound, although sulphamethoxazole was more active by weight, and suggest that both drugs ultimately interfere with nucleic acid synthesis.