Genus Rickettsia: R. prowazekii, R. conorii

• What is the Gram staining characteristic of Rickettsia?

  Gram -ve (hardly stains)
• What shape do Rickettsia bacteria have?

  Coccobacillary shape
• Why are Rickettsia considered obligate intracellular organisms?

  They cannot produce sufficient ATP, CoA & NAD
• What is a notable feature of Rickettsia's morphology?

  Highly pleomorphic
• What are the two main groups of Rickettsia?

  • Spotted fever group: Rickettsia rickettsia, Rickettsia akari
  • Typhus group: Rickettsia prowazekii, Rickettsia typhi
• What are the two main strains of Rickettsia?

  Rickettsia prowazekii and Rickettsia rickettsii
• What are the virulence factors of Rickettsia?

  • Type IV Secretion System
  • Surface Adhesion Proteins OmpA & OmpB
• What is the function of the Type IV Secretion System in Rickettsia?

  Facilitates conjugation and protein transport
• What role does OmpA play in Rickettsia's virulence?

  Key for evasion of host defense mechanisms
• What is the pathogenesis of Rickettsia infection?

  Invades capillary endothelium causing inflammation
• What are the clinical manifestations of Rickettsia infection?

  • Headache
  • Fever
  • Vasculitis
  • Vasculitis associated rash
• What is the Weil-Felix Agglutination Test used for?

  Diagnosis of Rickettsia infections
• What is the treatment for Rickettsia infections?

  Doxycycline
• What should be given to pregnant women infected with Rickettsia?

  Chloramphenicol
• What is the reservoir for Rickettsia prowazekii?

  • Humans (Body Louse)
• How is Rickettsia prowazekii transmitted?

  Through lice or human louse
• What are the clinical manifestations of Epidemic Typhus caused by Rickettsia prowazekii?

  • Incubation: 1-2 weeks
  • Granulomas in all organs
  • Rash starts at trunk, spreads outward
  • Myalgia and arthralgia
  • Pneumonia and encephalitis
  • Bril-Zinsser Disease (delayed relapse)