MICROBIOLOGY

• 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.