False-colour transmission electron micrograph (TEM) Chlamydia sp. , a genus of small, spherical bacteria which are obligate intra-cellular parasites. This section shows the organisms (pink spheres) within a human cell. Chlamydia trachomatis includes strains responsible for the sexually- transmitted disease lymphogranuloma venereum and the eye disease trachoma and inclusion conjunctivitis (TRIC). Presence of C. trachomatis in the human genital tract accounts for many cases of non-specific urethritis (NSU), which responds to treatment with erythromycin or tetracycline. Magnification: x 17, 000 at 35mm size, x34,000 at 6x7cm size.