Chlamydias

• What are the characteristics of Chlamydias?


  • Very small, like a virus, but possess DNA, RNA, and 70S ribosomes
  • non-motile and do not have cell walls
  • have two membranes without any peptidoglycan between them
• What type of bacteria are Chlamydias?


  • Obligate intracellular parasites; can grow and multiply only within the vesicle of host cells, similar to Rickettsia
• Do they have vectors of hosts?


  • do not have arthropods as vectors or hosts -> Direct physical contact for inhaling
• What forms does the unique developmental cycle involve?

  1. Elementary body (EB)
  2. Reticulate body (RB)
• What are the two species that cause disease in humans?

  • Chlamydia trachomatis
  • Chlamydophila psittaci
• What are elementary bodies?


  • tiny cocci
  • dormant infective forms (sporelike)
• What are Reticulate bodies?


  • larger pleomorphic
  • metabolically active
  • noninfective forms
• Where do the EB and RB occur? 


  • can occur within the phagosome of a host cell
• What do EB and RB prevent?


  • the fusion of phagosome with lysosome
  • can survive within a phagosome
• What do EB and RB lack?


  • lack enzymes to synthesize ATP
  • "Energy parasites"
• What are the 6 steps of Chlamydia pathogenesis?


  1. EB attaches to receptor on host cell (0 hours)
  2. EB enters host cell via endocytosis.
  3. EB converts into RB on vesicle (10 hours).
  4. RB divides rapidly, resulting in multiple RBs in an inclusion body.
  5. Most RBs convert back into EBs (21 hours).
  6. EBs are released from host cells (40 hours).