Chlamydia pneumoniae

Valeria Fabre, M.D.


  • C. pneumoniae is an obligate intracellular Gram-negative bacterium.
    • It grows like a virus (requires cell culture systems) but is a bacterium with RNA and DNA.
    • An intracellular organism parasite requires a host cell for ATP/GTP.
    • Known to also cause disease in koalas, reptiles and amphibians.
  • The elementary body is metabolically inactive and has a rigid cell wall that permits survival outside the cell and is infectious [Fig]. Inside the cell, it is seen as a reticulate body that is metabolically active but non-infectious.
  • Incubation culture to positivity: average 21 d.
  • Historically known as the "TWAR" agent, two of the original isolates were from Taiwan.
    • Formerly called Chalmydophila pneumoniae.

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Last updated: February 8, 2023