Isolation of Yersinia pseudotuberculosis from water

In recent years, a number of sporadic or community infections of Yersinia pseudotuberculosis were observed in several mountain area of Okayama Prefecture, Japan. Epidemiological observations strongly suggested that drinking water in those areas, i.e. non-chlorinated water from mountain stream or wells, must be the source of the infection, so we examined the waters from the epidemic areas to detect the organisms. The examinations revealed the germs in the waters; the contamination rate of water from the northern areas is higher than that from the southern urban regions. The isolation procedures for the germs were also studied and improved. The media added with blood or hemin proved to be better for isolation of the organism.