Distribution and effects of a defined six-member murine-derived microflora in gnotobiotic gerbils.

The gnotobiotic gerbil was selected as a model with which to study the effects of colonization with a defined microflora on organ morphology, histology, and selected blood biochemical parameters. Gerbils were maintained germfree for 13 months but failed to reproduce, presumably because of the enlarged cecum. A colony of gnotobiotic gerbils that was associated with a bacterial flora consisting of Lactobacillus brevis, Streptococcus faecalis, Staphylococcus epidermidis, Bacteroides vulgatus, Enterobacter aerogenes, and a Fusobacterium sp. was established. These gnotobiotic gerbils had smaller ceca than germfree gerbils and proved capable of reproduction. Except for the presence of large numbers of Bacteroides organisms in the stomach and greater numbers of S. epidermidis in gnotobiotic gerbils, the number and location of gastrointestinal bacteria were similar in conventional and gnotobiotic gerbils. Bacteroides sp. was the second most predominant microorganism present in gnotobiotic gerbils, whereas clostridia were reported to be the second most predominant microorganism in conventional gerbils. Microscopic examination of direct-impression smears indicated that fusobacteria were present on mucosal surfaces. Intestines of gnotobiotic gerbils weighed twice as much as the intestines of conventional gerbils. Intestinal tissue water weight values from conventional and gnotobiotic gerbils were similar. Histological examination of gerbil intestinal tissue revealed no cellular hypertrophy and no evidence of inflammation in gnotobiotic gerbil intestines. Spleens of gnotobiotic gerbils showed no germinal center stimulation. Statistical differences in total serum glucose, serum protein, and hematocrit levels were found between conventional and gnotobiotic gerbils.