Yersinia

Yersinia is a genus of bacteria in the family Yersiniaceae. Yersinia species are Gram-negative, coccobacilli bacteria, and are facultative anaerobes. Three members of Yersinia are pathogenic in humans: Y. pestis causes the plague and Y. enterocolitica and Y. pseudotuberculosis cause gastrointestinal syndromes. Rodents are the natural reservoirs of Yersinia; less frequently, other mammals serve as the host. Infection may occur either through blood (in the case of Y. pestis) or in an alimentary fashion, occasionally via consumption of food products (especially vegetables, milk-derived products, and meat) contaminated with infected urine or feces.

Speculations exist as to whether or not certain Yersinia can also be spread by protozoonotic mechanisms, since Yersinia species are known to be facultative intracellular parasites; currently, there are studies and discussions of the possibility of amoeba-vectored (through the cyst form of the protozoan) Yersinia propagation and proliferation.