Genus Ricksttsia. Flashcards
1
Q
Classification
A
Family: Rickettsiaceae
Genus: Rickettsia
Typhus group
( 3 species)
Spotted fever group
SPECIES
R.rickettsii —> Rocky Mountain spotted fever (focus)
R.akari —> Rickettsial pox
2
Q
Rickettsia rickettsii
A
Rickettsia rickettsii
- Dermacentor ticks are both the vector and main reservoir
- transmission via tick bite
3
Q
Morphology
A
- gram negative rod
- pleomorphic
4
Q
Growth characteristics
A
- aerobic
- obligate intracellular parasite
- Fastidious: CoA and NAD+ needed for growth —> provided by the host
5
Q
Antigenic structure
A
Dominant outer membrane proteins:
- OMP A
- OMP B
Alkali stable polysaccharide
Shares antigens with proteus
- antigens cross react with OX strains of Proteus vulgaris (Weil-Felix reaction)
6
Q
Virulence factor
A
No toxins or virulence factors are known
7
Q
Disease
A
Rocky Mountain spotted fever
> rash does not start immediately —> incubation period of 2 days to 2 weeks
rash of different ages
rash progresses from the extremities —> spreads centrally
- fever
- headache
- myalgia
8
Q
Microbiological diagnosis
A
- antibody detection in serologic tests such as ELISA
- Weil-Felix test is no longer used
- Stain and culture are rarely performed
9
Q
Treatment and prevention
A
- tetracycline
Prevention
No vaccine
> protective clothing and prompt removal of ticks
