trachomatis

Chlamydia trachomatis is a gram-negative, obligate intracellular bacterium and a member of the family Chlamydiaceae. It infects humans and exists in a biphasic developmental cycle, alternating between infectious elementary bodies (EBs) and replicative reticulate bodies (RBs) within host cells.

Strains are classified into serovars: A-C cause trachoma; D-K cause urogenital infections and neonatal conjunctivitis; L1-L3 cause lymphogranuloma venereum (LGV).

Transmission occurs mainly through sexual contact; vertical transmission during birth can cause neonatal conjunctivitis or pneumonia; ocular trachoma spreads by contact with contaminated secretions.

Clinical manifestations: Trachoma is a chronic conjunctivitis leading to eyelid scarring, trichiasis, corneal opacity and potential blindness. Urogenital infections are often asymptomatic but can cause cervicitis, urethritis, pelvic inflammatory disease, and complications. LGV presents as painful inguinal syndrome or proctocolitis with tender buboes.

Diagnosis: NAATs (nucleic acid amplification tests) on vaginal, cervical, urethral, or urine samples are standard; conjunctival swabs for ocular infection; culture is less common. Serology has limited role except in suspected LGV cases.

Treatment: For uncomplicated urogenital infections, azithromycin 1 g orally once or doxycycline 100 mg twice daily for 7 days. In pregnancy, azithromycin is preferred. For LGV, doxycycline 100 mg twice daily for 21 days. Alternative regimens exist for ocular disease and pregnancy.

Prevention and public health: safe sex practices, routine screening in at-risk populations, partner notification; in endemic regions for trachoma, the SAFE strategy (Surgery, Antibiotics, Facial cleanliness, Environmental improvement) is used to reduce transmission.

Epidemiology: one of the most common bacterial sexually transmitted infections worldwide; trachoma remains a leading cause of preventable blindness in certain areas, particularly where water and sanitation are limited.