Chlamydia trachomatis

Walid El-Nahal, M.D., Annie Antar, M.D.


  • The many serovars of C. trachomatis can generally be divided into:
    • Serovars D-K: cause genitourinary tract disease, rectal disease (including proctitis), and conjunctivitis.
    • Serovars L1-L3: cause lymphogranuloma venereum (LGV) and proctocolitis.
    • Serovars A-C: causing endemic trachoma (chronic keratoconjunctivitis) in resource-limited tropical settings, leading infectious cause of blindness worldwide.
  • Obligate intracellular bacteria, infecting primarily ocular and genitourinary epithelium; one of the smallest known bacterial genomes.
  • All Chlamydia species have 2 distinct forms in their infectious cycle:
    • Elementary body (EB - infectious, extracellular sporelike form)
    • Reticulate body (RB - intracellular, metabolically active, replicating form).
    • The EB penetrates a cell, transforms into an RB to replicate, then eventually the cell ruptures releasing EBs that can infect new cells.
  • Requires cell culture for propagation.
  • Immunity is short-lived, which explains the frequency of re-infection.

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Last updated: October 19, 2022