**5. Chlamydia**

*Chlamydia trachomatis* is a small, obligate intracellular bacterium that typically infects nonciliated epithelial cells of mucous membranes; urethral epithelial cells in males and columnar epithelial cells of the endocervix in women. However in the lymphogranuloma venereum serovars, macrophages appear to be the principal host cell. *Chlamydia* is organized into multiple serovars that cause a diverse variety of human disease. Serotypes A, B, Ba, and C are the agents of classic blinding trachoma. Serotypes D thru K can cause adult inclusion and neonatal conjunctivitis, pneumonia, urogenital infections and Reiter's syndrome. Serotypes L1, L2, and L3 infect tissues deeper to the epithelium and cause lymphogranuloma venereum (LGV).
