Download Rickettsia

Rickettsia
• Rickettsia is a diverse collection of
obligate intracellular parasites found in
ticks, lice, fleas, mites and mammals
• Smaller than bacteria and the other
biological characteristics are similar to
bacteria (e.g., binary fission, cell wall,
sensitive to antibiotics, containing DNA
and RNA).
• There are 5 genera in Rickettsia
– Rickettsia
– Ehrlichia
– Orientia
– Coxiella
– Bartonella
• Many species of Rickettsia cause
zoonosis in human (rickettsial diseases)
mediated by the arthropods (节肢动物).
• R. prowazekii: human louse (vector),
epidemic typhus.
• R. mooseri: mouse flea (vector),
endemic typhus (斑疹伤寒).
• O. tsugamushi: Chigger (vector), scrub
typhus (恙虫病).
• C. burnetii: tick (vector), Q fever.
Virulent factors
• phospholipase A
• LPS
• capsule
• Laboratory diagnosis: Isolation and culture,
PCR, serological examinations and Weil-Felix
test.
• Weil-Felix test: Because somatic antigens
of Bacillus proteus strains (OX-K and OX19)
have common antigens with Orientia
tsugamushi (OX-K), Rickettsia prowazekii
(OX19) and Rickettsia mooseri (OX19), they
are used to detect serum antibodies of
patients with rickettsial diseases.
• Treatment: Tetracycline is the first choice
for therapy.
• Prevention: No vaccine is available.