🦠microbiology review

R. rickettsii

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Rickettsia rickettsii is a gram-negative, intracellular bacterium that causes Rocky Mountain spotted fever. It primarily infects endothelial cells and is transmitted to humans through tick bites.

5 Must Know Facts For Your Next Test

  1. R. rickettsii belongs to the Alphaproteobacteria class within the Proteobacteria phylum.
  2. The primary vectors for R. rickettsii are ticks, specifically the American dog tick and the Rocky Mountain wood tick.
  3. Infection with R. rickettsii can lead to severe symptoms including fever, rash, headache, and potentially fatal multi-organ failure if left untreated.
  4. R. rickettsii's pathogenesis involves escaping the phagosome and replicating in the host cell cytoplasm.
  5. Diagnosis often involves serological tests or PCR to detect R. rickettsii DNA in clinical samples.

Review Questions