ABSTRACT

The first visualization of Yersinia pseudotuberculosis was made by L. Malassez and W. Vignal in 1883. Y. pseudotuberculosis is a pleomorphic Gram-negative coccobacillus whose morphology varies from coccoid to rod-shaped with rounded ends. Y. pseudotuberculosis is characteristically nonmotile at 37°C and motile at 25°C. Y. pseudotuberculosis is a facultative anaerobe that grows well on ordinary media, i.e., nutrient agar, tryptic soy agar, blood agar, and chocolate agar. Although Y. pseudotuberculosis grows well on ordinary media after primary isolation, initial isolation from human or animal specimens may require special handling to be successful. Y. pseudotuberculosis strains, unlike Y. enterocolitica, are exceptionally constant in their biochemical characteristics with only rare individual strain variation. Differentiation of Y. pseudotuberculosis and Y. pestis can usually be accomplished by testing for motility at 20 to 25° C, for production of urease, and for acid production from rhamnose and melibiose.