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.