Rickettsial Infections

Question 1

Rickettsiae

Answer 1

Gram (-) coccobacillus
Obligate intracellular pathogens
Replicate by binary fission- can synthesize their own ATP
Induce endocytosis in the host cell and replicate in the cytoplasm of the host cell, then killing them
Target is endothelial cell of capillaries and other small blood vessels.
Produce necrotizing vasculitis

Question 2

Rickettsia rickettsii

Answer 2

Rocky Mountain Spotted Fever- acute, potentially fatal, systemic vasculitis
Transmitted by ticks
Rash, produced by inflammatory damage to cutaneous vessels, most visible manifestation. Cutaneous lesions appear on palms and soles.
Spreads to vascular smooth muscle and endothelium of larger vessel walls .

Question 3

Rickettsia prowazekii

Answer 3

Typus- Louse-borne
Inoculates abrasion or inhaled
Begins as a localized vasculitis then progresses to a systematic vasculitis.
**Can establish latent infection and produce recrudescent disease (Brill-Zinsser Disease)

Question 4

Ricketsita typhi

Answer 4

Endemic (murine) typhus
Transmitted through fleas
If inhaled can cause pulmonary infection.

Question 5

Rickettsi tsutsugamushi

Answer 5

Scrub Typus (tsutsugamuchi fever) is an acute febrile illness of humans.
Transmitted form chiggers (mite)
Rickettsemia, lymphadenopathy, pneumonia, macular rash, hepatosplenomagaly
Severe infections are complicated by myocarditis, meningioencephalitis & shock.

Question 6

Coxiella burnetti

Answer 6

Q Fever- self-limited, systemic infection.
Gram (-) pleomorphic coccobacillus
After inhalation, enter cells passively upon phagocytosis by alveolar macrophages, replicate in phagolysosome. Lungs & liver most prominently associated
DOES NOT produce vasculitis, NO associated rash
Exposure to animals or animal products