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