Yersinia enterocolitica bacteria may be isolated from soil, water, animals, and a variety of foods. The genus Yersinia includes 11 species, 3 of which are potentially pathogenic to humans: Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica. Y. enterocolitica is most important as a cause of foodborne illness. Refrigerated foods are potential sources of the bacteria: contamination is possible at the manufacturing site or in the home. This bacterium survives and grows during refrigerated storage. (Enhanced SEM, microscope magnification 8,000x, image width: 16 micrometers. bar: 2 micrometers)