Elimination of microbial flora from conventionally raised Syrian hamsters by antimicrobial agents

An attempt was made to identify and eliminate the normal endogenous microflora from conventionally-raised Syrian hamsters. A total of 14 bacterial and 2 yeast species were identified using enrichment, differential and selective media. The elimination of endogenous flora was carried out in two steps. In each step, hamsters were given a filter-sterilized mixture of two or more antibiotics for 10 weeks continuously through drinking water. During the second week, the hamsters were immersed once into a germicidal solution then housed in horizontal laminar-flow units. They were monitored at weekly intervals for the presence or absence of microorganisms in their fecal samples and fur swabs which were cultured on media as mentioned above. In step I, up to four resistant bacteria were cultured. On the basis of the antibiotic sensitivity profile of the surviving bacteria, step II procedure was started. The antibiotic mixture containing Kanamycin and Amphotericin B was fatal for the hamsters in both steps. Within 4 to 5 weeks of step II, all groups of hamsters tested bacteria-free and remained so for the duration of the step. Two weeks following withdrawal of antibiotics from drinking water, only one group of hamsters showed the presence of Escherichia coli. The other groups of hamsters tested bacteria-free for the 5 week duration of the experiment. The autopsies of these hamsters revealed greatly enlarged and thin-walled cecums, a characteristic of the germfree state.