What is yersinia?

Yersinia is a genus of bacteria in the family Enterobacteriaceae named for A.E.J. Yersin, a Swiss bacteriologist, who discovered the Yersinia pestis bacterium - cause of plague. The special genus Yersinia is recognized since 1971 (mainly for taxonomic reasons). 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. Natural reservoirs of Yersinia bacteria are rodents and sometimes (less frequently) other mammals. Infection may occur either through blood (e.g. as in the case of Y. pestis) or in an alimentary fashion, through consumption of products (esp. 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.
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.
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.

I'm a Virgo :)

Yersinia is a genus name for a microorganisms. Those that belong in genus is organisms like Yersinia pestis ( organism that causes bubonic plague .. yuck!) and Yersinia enterocolitica an organism that can survive pasteurization time in dairy products like milk and still grow in fridge temperture (5-7 C) and cause food borne illness. Both of these organisms are gram negative.

YOu probably meant yersinosis .

It's a gastrointestinal disease that's caused by organisms in genus Yersinia, Yersinia enterocolitica. They infect you and they cause diahrriea, vomiting , stomach ache, and fever. You get it from eating meat, milk that's contaminated with it .

Y. enterocolitica, a small rod-shaped, Gram-negative bacterium, is often isolated from clinical specimens such as wounds, feces, sputum and mesenteric lymph nodes. However, it is not part of the normal human flora. Y. pseudotuberculosis has been isolated from the diseased appendix of humans.