Epidemic infection caused by Citrobacter rodentium in a gerbil colony

Non-motile, Gram-negative rods, isolated from the intestinal tract and kidn ey of several dead animals in a gerbil colony, were identified as Citrobact er rodentium (formerly included in C freundii species) on the basis of 31 b iochemical tests. The isolates were tested against 40 antimicrobial agents and were all susceptible to ticarcillin plus clavulanate, ceftazidime and m ost of the quinolones studied, but were all resistant to most of the penici llins and aminoglycosides tested, and to fosfomycin, metronidazole and tiam ulin. This bacterial species has been primarily associated with transmissib le murine colonic hyperplasia, and this appears to be the first report of a n epidemic infection in a gerbil colony with a fatal outcome in most of the animals affected.