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Bergey’s “oddball” Gram negatives

Bergey’s “oddball” Gram negatives. *Obligate intracellular parasites: Rickettsia Chlamydia *Bacteria lacking cell walls: Mycoplasma Spiroplasma. Rickettsia and Chlamydia. Almost all are obligate intracellular parasites  grow and reproduce only in host cells

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Bergey’s “oddball” Gram negatives

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  1. Bergey’s “oddball”Gram negatives *Obligate intracellular parasites: Rickettsia Chlamydia *Bacteria lacking cell walls: Mycoplasma Spiroplasma

  2. Rickettsia and Chlamydia • Almost all are obligate intracellular parasites  grow and reproduce only in host cells • Metabolically incomplete  they cannot synthesize all necessary metabolic molecules • Resemble viruses (small size and intra-cellular requirement for reproduction)

  3. Rickettsia • ca of RMSF, typhus and others • Transmitted by blood sucking arthropod (tick, flea, louse) • Animal or insect reservoir • Infects endothelial cell – produces vasculitis/ vascular obstruction -> producing small hemorrhages -> rash

  4. Rocky Mt Spotted Fever • ca is R. rickettsia • Found in young people • Transmitted by ticks • Most cases east of Miss! • Misdiagnosed as measles • Case fatality rate is high • Treat with chloramphenicol • Death due to: • Hypotension • Intravascular coagulation

  5. Incidence of RMSF - 2002

  6. Epidemic typhus • typhus = “stupor” • c.a. is R. prowazekii • Transmitted by body lice – typically among crowded populations • High prolonged fever • Vasculitis/coagulation • Vaccines available for military

  7. Louse (lice) life cycle

  8. Endemic typhus (found in US) • c.a. is R. typhi • Usually not fatal • Rat flea vector • Rodent reservoir • Sometimes referred to as “murine typhus”

  9. Chlamydia • Important pathogen in humans and animals • Includes two morphological types within its life cycle • Elemental body = infectious form; attaches to cell surfaces – stimulates phagocytosis • Reticulate body = reproductive form; acquires host ATP, divides within and kills host cell Diagnosed as “inclusion bodies” within epithelial cells

  10. Chlamydia trachomatis I • c.a. of most common STD (4 million/yr) in the U.S. • Produces NGU • Can be self-limiting • Sensitive to antibiotics • Males – purulent urethral discharge • Females – many asymptomatic • Can lead to PID in women • Opthalmia neonatorum to neonate

  11. Chlamydia trachomatis II • Lymphogranuloma venereum (LGV) • Caused by strains of Ct that invades and infects lymphoid tissue • Enlarged local lymph nodes • Esp. near genital area

  12. Chlamydia trachomatis III • “trachoma” = #1 cause of blindness worldwide • ~500 million affected • Transferred by flies, infected fingers, infective discharges on bedding, pillows, etc. • Damage to cornea invites secondary infection  blindness

  13. Chlamydia psittaci • c.a. of psittacosis • Produces atypical pneumonia • Transmitted by infected psittacine birds to humans or to poultry plant workers • Parrots quarantined prior to sale

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