Rickettsia prowazekii is a species of gram-negative, obligate intracellular parasitic, aerobic bacilliform bacteria of class Alphaproteobacteria that is the etiologic agent of epidemic typhus, transmitted in the feces of lice. In North America, the main reservoir for R. prowazekii is the flying squirrel. R. prowazekii is often surrounded by a protein microcapsular layer and slime layer; the natural life cycle of the bacterium generally involves a vertebrate and an invertebrate host, usually an arthropod, typically the human body louse. A form of R. prowazekii that exists in the feces of arthropods remains stably infective for months. R. prowazekii also appears to be the closest semi-free-living relative of mitochondria, based on genome sequencing.

This bacterium lacks flagella and is aerobic. It is classed gram-negative because its cell walls do not retain crystal violet Gram stain; gram-negative bacteria in general are more resistant to many antibiotics such as penicillin.

Genome

The genome of R. prowazekii is reduced, being about 1Mb in size and encoding 834 proteins. Some strains encode 866 proteins.

Treatment

Vaccines against R. prowazekii were developed in the 1940s, and were highly effective in reducing typhus deaths among U.S. soldiers during World War II. Immunity following recovery from infection with, or by immunization against, R. prowazekii is lifelong in most cases. However, R. prowazekii can establish a latent infection, which can reactivate after years or decades (referred to as Brill-Zinsser disease). Treatment with tetracycline antibiotics is usually successful.

References

  • Rickettsia prowazekii Taxon Overview at Virginia Bioinformatics Institute
  • NIAID Biodefense Research Agenda for Category B and C Priority Pathogens from the US National Institute of Allergy and Infectious Diseases