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Variations of plasmid content in Rickettsia felis

Pierre-Edouard Fournier1, Lokmane Belghazi, Catherine Robert

  • 1Unité des rickettsies, IFR 48, CNRS-IRD UMR 6236, Faculté de médecine, Université de la Méditerranée, Marseille, France.

Plos One
|May 30, 2008
PubMed
Abstract

Insights

Rickettsia felis (R. felis) contains up to two plasmid forms, but this content is unstable and varies with culture passage history. This bacterium belongs to the spotted fever group rickettsiae.

Area of Science:

  • Microbiology
  • Genomics
  • Phylogenetics

Background:

  • Rickettsia felis (R. felis) characterization has been debated due to R. typhi contamination.
  • Initial studies placed R. felis within the spotted fever group, with genome data suggesting two plasmid forms.
  • A recent bioinformatic study challenged the presence of the second plasmid form and proposed a new R. felis phylogenetic group.

Purpose of the Study:

  • To unambiguously confirm the presence of plasmid forms in R. felis.
  • To investigate the influence of culture passage history on R. felis plasmid content.
  • To determine the optimal culture conditions for R. felis.
  • To confirm the phylogenetic position of R. felis.

Main Methods:

  • Polymerase Chain Reaction (PCR) to detect plasmid forms.
  • Cultivation of R. felis at different temperatures (30°C and 37°C) in Vero cells.
  • Phylogenetic analysis using 667 concatenated core genes.

Main Results:

  • Confirmed the presence of two plasmid forms in R. felis strain URRWXCal(2) (T) via PCR across multiple independent laboratories.
  • Demonstrated that R. felis plasmid content (0-2 forms) is dependent on culture passage history.
  • Established that R. felis forms plaques at 30°C but not at 37°C in Vero cells.
  • Phylogenetic analysis confirmed R. felis's position within the spotted fever group.

Conclusions:

  • Rickettsia felis unambiguously belongs to the spotted fever group rickettsiae.
  • R. felis may harbor up to two plasmid forms, but this plasmid content is unstable.
  • Culture conditions and passage history significantly impact R. felis plasmid carriage.

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