Micro| Chlamydia Species

3.27 Chlamydia Species Microbiology review for the USMLE Step 1 exam Chlamydia is a gram-negative bacteria that is an obligate intracellular organism. It has a two-part life cycle involving the reticular body (active form) and elementary body (inactive form). There are three main species of chlamydia that cause human infections: chlamydia trachomatis, chlamydia pneumoniae, and chlamydia psittaci. Chlamydia trachomatis is the most common sexually transmitted infection in the US and causes genital tract infections, lymphogranuloma venereum, pelvic inflammatory disease, and reactive arthritis. Treatment for chlamydia trachomatis includes azithromycin or doxycycline, and ceftriaxone is often added to cover Neisseria gonorrhoeae. Chlamydia trachomatis can also infect neonates during delivery, causing conjunctivitis and pneumonia. Chlamydia pneumoniae causes community-acquired pneumonia spread through respiratory droplets. Chlamydia psittaci is associated with pet birds and also causes pneumonia.