Plesiomonas shigelloides is a species of bacteria and the only member of its genus. It is a Gram-negative, rod-shaped bacterium which has been isolated from freshwater, freshwater fish, shellfish, cattle, goats, swine, cats, dogs, monkeys, vultures, snakes, toads and humans. It is considered a fecal coliform. P. shigelloides is a global distributed species, found globally outside of the polar ice caps.

P. shigelloides has been associated with the diarrheal disease state in humans, but has been identified in healthy humans as well. It can enter the body either through contact with water contaminated by fecal matter or through seafood originating from a contaminated source.

Classification

P. shigelloides was originally considered part of the family Vibrionaceae, but is generally accepted to be part of Enterobacteriaceae due to the similarity of its 5S rRNA sequence to other members of Enterobacteriaceae'. The rRNA sequence of P. shigelloides has been found to be most similar to Proteus mirabilis, and as a result it is now considered part of the tribe Proteeae within the family Enterobacteriaceae. P. shigelloides is the only known member of its genus.

Ecology

Growth

P. shigelloides is incapable of surviving in saltwater environments where the concentration of salt is greater than 4% and has been found to tolerate pH ranges between 4.5 and 9. Plesiomonas can be distinguished from Shigella in diarrheal stools by an oxidase test: Plesiomonas is oxidase positive and Shigella is oxidase negative. Plesiomonas is easily differentiated from Aeromonas sp. and other oxidase-positive organisms by standard biochemical tests.

Pathogenicity

P. shigelloides produces a cytoxic-enterotoxin (LCE) which induces rapid death in mice. LCE is the first virulence factor identified in P. shigelloides that is exported through membrane vesicles. Freshwater fish can often be infected with P. shigelloides which can be lethal depending on the concentration of the bacterium in their bodies.

References

  • Type strain of Plesiomonas shigelloides at BacDive - the Bacterial Diversity Metadatabase