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Flashcards in Rickettsia Deck (9)
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1
Q

Rickettsia

Morphology

Habitat

Transmission

A

A small 0.2-0.4 uM, gram negative, non-motile.

Has a permeable cell wall that is weak and pleomorphic, and no capsule

Obligate intracellular ATP parasite

Rodents are reservoir and the vector of transmission is fleas, ticks, lice.

Prefer to attack endothelial cells of the blood vessels.

2
Q

Rickettsia

Virulence factors and Antigens

A

Rickettsia shares some antigens with Proteus vulgaris: OX-2, OX-19, and OX-K.

3
Q

What are the two species of Ricketssia that cause spotted fevers?

What diseases do they cause?

How are they transmitted?

A

Rickettsia rickettsii - Rocky mountain spotted fever

Transmitted by ticks over 6-8 hours of attachment.

Fever, conjuntivitis, severe headache,

Red spotted rash (petechia) appearing on the wrists, palms, ankles, and soles feet, then moving to the trunk

Treat with doxycycline and chlormaphenicol (macrolide)

Rickettsia akari - Rickettsial Pox

Transmitted by mites that can be found on house mice.

Rickettsialpox - mild, self limiting fever and headache, and a blister that forms at the bite site.

Treat with doxycycline (tetracycline)

4
Q

Rickettsia

Culture

A

Can only be cultured in living cells, is kept in innoculated embrionated eggs, lab animals, or tissue culture

Direct smear can be stained with Giemsa stain showing intracellular bacteria.

5
Q

What are the major pathogenic species of Rickettsia? (4)

What are the names of the diseases the cause?

A
  • R. rickettsii -* Rocky mountain spotted fever
  • R. akari* - Ricketsialpox
  • R. prowazekii* - Epidemic typhus
  • R. typhi* - Endemic typhus
6
Q

R. prowazekii

Transmission

Clinical disease

A

Causes Epidemic Typhus

Spread human to human by lice

Sudden onset fever, myalgia, spotted rash on the trunk, and organ failure

A patient may recover, but then still have a latent asymptomatic infection, which then re-emerges as Brill-Zinsser Disease, The same disease in a milder form, but with no skin rash

7
Q

Rickettsia typhi

Clinical disease

Transmission

A

Causes Murine Typhus or Endemic Typhus

Transmitted by a flea, and not human-to-human

Causes same disease (Typhus) as R. prowazekii but in a milder form.

Headache, Fever, Trunk rash, Delerium, Coma

8
Q

Rickettsia tsutsugamushi

Clinical Disease

A

Causes: Scrub typhus, found in Asia and the pacific.

Spread by mite larvae.

High fever, headache, and scab at the bite site.

The bacterium itself has been re-classified as Orientia tsutsugamushi, and is actually of a serparate genus than Rickettsia, but is still in the family Rickesttsiae.

9
Q

`Rickettsia diseases

Diagnosis

A

Weil-Felix reaction: Uses the cross reactin Proteus vulgaris antigens: OX-2, OX-19, and OK-K

Latex bead agglutination test, coated with these antigen.

Different specific Rickettsia species prodeuce a different specific antibody responses, usually to just one or tow of these specific antigens.