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.