The genus Yersinia comprises Gram-negative coccobacilli, of which 3 species—Y. pestis (the plague bacillus), Y. pseudotuberculosis, and Y. enterocolitica—are well-known human pathogens. However, not all strains of Y. enterocolitica are capable of causing human intestinal infections. Primarily on the basis of biochemical reactions, Y. enterocolitica has been classified1 into 6 biogroups that have distinct patterns of serogroup designations, human pathogenic potential, and ecologic and geographic distribution (Table 9280:1). Isolates belonging to biogroup 1A (positive for salicin fermentation, esculin hydrolysis, and pyrazinamidase production) are thought to be incapable of causing human intestinal infections, whereas isolates negative for these traits are more likely to cause intestinal infections, which include enterocolitis, mesenteric adenitis, or terminal ileitis.
Yersinia enterocolitica are Gram-negative bacteria that can cause acute intestinal infection and can be found in cold or temperate US climates.2,3 It is widespread in nature and occurs in the gastrointestinal tract of numerous animal hosts, including mammals associated with aquatic habitats, avian species, and cold-blooded species.4 From these reservoirs, terrestrial and aquatic ecosystems may become contaminated and human infections may ensue. Some animal hosts (e.g., domestic dogs and cats and farm animals) carrying pathogenic Y. enterocolitica are likely to come in contact with humans either directly or via ingestion (e.g., pork).5,6