Light micrograph (dark field) showing presence of Chlamydia trachomatis (yellow bodies), a virus- like bacteria that causes eye, genital and generalized systemic diseases in man. Here, the chlamydial cells have been stained with a fluorescent antibody. Genital chlamydial infections include urethritis in men, cervicitis in women and lymphogranuloma venereum, a venereal disease more common in Tropical regions. C. trachomatis is the commonest cause of nonspecific urethritis (NSU) in men and cervicitis in women. Untreated, the infection may lead to pelvic inflammatory disease in women which may cause sterility. Treatment is with suitable antibiotics.