Yersinia

Yersinia is a genus of bacteria in the family Enterobacteriaceae. Yersinia are Gram-negative rod shaped bacteria, a few micrometers long and fractions of a micrometer in diameter, and are facultative anaerobes. Some members of Yersinia are pathogenic in humans. 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, through 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 via  protozoonotic mechanisms, since Yersinia are known to be facultative intracellular parasites; studies and discussions of the possibility of amoeba-vectored (through  the cyst form of the protozoan) Yersinia propagation and proliferation are now in progress.

Microbial physiology
An interesting feature peculiar to some of the Yersinia bacteria is the ability  not only to survive, but also to proliferate at temperatures as low as 1-4 degrees Celsius (e.g., on cut salads and other food products in a refrigerator). Yersinia representatives also reveal relatively high  heat resistantance, some of them being able to survive 50-60 degrees Celsius temperature for up to 20-30 minutes and (arguably, might be due to misreading of information like the first external link below) surviving standard pasteurization process (15 seconds at 72 degrees Celsius) in milk. Yersinia bacteria are relatively quickly inactivated by oxidizing agents such as hydrogen peroxide and potassium permanganate solutions.

Pathogenesis
The disease caused by Y. enterocolitica is called Yersiniosis. Another pathogen is Y. pseudotuberculosis, which is the least common species of Yersinia causing disease in humans. Yersinia is implicated as one of the pathogenic causes of Reactive Arthritis worldwide.

History
The genus is named for A.E.J. Yersin, a Swiss bacteriologist, who discovered the Yersinia pestis bacterium - the causative agent of the bubonic plague. The special genus Yersinia has been recognized since 1971, mainly for taxonomic reasons.