chlamydia

a genus of Gram-negative bacteria that are OBLIGATE intracellular parasites in humans and other animals, in which they cause disease. Chlamydia psittaci causes PSITTACOSIS , and C. trachomatis is the causative agent of the eye disease TRACHOMA . Some strains of Chlamydia, especially C. trachomatis, are a common cause of sexually transmitted infections, being responsible for nonspecific URETHRITIS in men, PELVIC INFLAMMATORY DISEASE in women, and INCLUSION CONJUNCTIVITIS in the newborn. C. pneumoniae causes pneumonia. - chlamydial adj.