Yersinia philomiragia sp. n., a new member of the Pasteurella group of bacteria, naturally pathogenic for the muskrat (Ondatra zibethica).

A bacterium experimentally pathogenic for muskrats (Ondatra zibethica), white mice, mountain voles (Microtus montanus), and deer mice (Peromyscus maniculatus) was isolated from the tissues of a sick muskrat captured on the Bear River Migratory Bird Refuge (Brigham City, Utah) and from four surface water samples collected within 15 miles of that point. In culture, the cells are chiefly coccoid, but in the tissues of muskrats and voles they resemble the bizarre forms of Yersinia pestis, except for their smaller size. The characteristics of the organism are described and the name Yersinia philomiragia sp. n. is proposed.