MICROBIOLOGY

• Chlamydiae are obligate intracellular bacteria, possess both DNA and RNA (a characteristic that distinguishes them from viruses), and have a cell wall similar to that of gram-negative bacteria.
• These organisms have a complex reproductive cycle and exist in two forms.
  • The elementary body (the infective form) is adapted for extracellular survival, while the reticulate body is adapted for intracellular survival and multiplication.
  • Within 18–24 h after infection of the cell, reticulate bodies have replicated and begun to condense into elementary bodies that are released to infect other cells or people.
• Three chlamydial species infect humans: Chlamydia trachomatis, C. psittaci, and C. pneumoniae.
  • CF tests and enzyme immunoassays that detect lipopolysaccharide identify chlamydiae only to the genus level.
  • The microimmunofluorescence (MIF) test can differentiate among the three species.
  • For a discussion of C. pneumoniae, see Chap. 100: Mycoplasma pneumoniae, Legionella Species, and Chlamydia pneumoniae.