Rickettsia, Chlamydia, Mycoplasma and other unusual bacteria

Major Pathogens

1. Rickettsia
   • Gram-negative intracellular parasites
   • Rod-shaped; PG and LPS present
   • Infect cells by phagocytosis, then lyse phagosome and multiply in cytosol
   • Energy parasites: use host cell's ATP
   • Vector-borne
   • Clinical diseases
     • R. rickettsii: Rocky mountain spotted fever
     • R. prowazekii: typhus fever
     • R. akari: Rickettsialpox
     • Orientia tsutsugamushi: Scrub typhus
2. Chlamydia
   • Gram-negative intracellular parasites
   • Lack peptidoglycan in their cell walls
   • Complex life cycle with elementary body and reticulate body
   • Infect nonciliated epithelial cells (urethra, conjunctiva, lungs)
   • Clinical diseases
     • Trachoma conjunctivitis
     • Urogenital infections (Chlamydia)
     • Lymphogranuloma venereum (LGV)
3. Chlamydophila 
   • Gram-negative intracellular pathogen
   • Clinical diseases
     • Pneumonia (C. pneumoniae)
     • Psittacosis (C. psittaci)
4. Ehrlichia
   • Gram-negative tiny rods; Vector-borne
   • intracellular pathogens in phagocytic white blood cells 
   • Lack Peptidoglycan + LPS (not endotoxic)
   • Survives by inhibiting phagolysosme fusion
   • 2 forms: EB and RB; morula
   • Clinical diseases
     • Ehrlichiosis
     • Anaplasmosis
5. Coxiella
   • Gram-negative intracellular pathogens
   • Very small; PG and LPS present
   • Multiply in various organs
   • Clinical Disease
     • Q-fever
6. Mycoplasma
   • Cell wall-less bacterium (Gram-positive by phylogeny)
   • Aerobic; produce P1 adhesin (superantigen)
   • Most prevalent in 5 - 15 year-old
     • Pneumonia (primary atypical)
     • Non-gonococcal urethritis (M. genitalium)
     • Pelvic inflammatory disease (M. hominis)
7. Ureaplasma
   • Non-gonococcal urethritis

Major Diseases

1. Rocky mountain spotted fever
2. Typhus fever
3. Trachoma
4. Chlamydia
5. Lymphogranuloma venereum (LGV)
6. Pneumonia
7. Psittacosis
8. Ehrlichiosis
9. Q-fever