Prevalence of Yersinia enterocolitica in waters of the lower Chippewa River Basin, Wisconsin.

Water samples collected over a 14-month period from the lower Chippewa River drainage basin in Wisconsin were examined for Yersinia enterocolitica with either MacConkey-Tween 80 agar or Y-M agar (T. N. Saari and G. P. Jansen, Contrib. Microbiol. Immunol. 5:185-196) as the selective medium. A new method of isolation was developed. Of 303 water samples, 8.25% were positive. A seasonal variation was noticed, with winter isolations being most frequent.