Effects of Age and Starvation on the Gastrointestinal Microflora and the Heat Resistance of Fecal Bacteria in Rats

Abstract

AbstractThe microflora of the gastrointestinal tract in rats 1 day to 100 weeks old, of the cecal contents and wall in starved rats, and of heat‐treated feces of normal rats was determined by cultural examination. Streptococci, staphylococci, lactobacilli, actinobacilli, and coliforms colonized the tract during the 1st week of life. Bacteroidaceae, veillonellae, catenabacteria (composed of eubacteria and anaerobic lactobacilli), clostridia, bifidobacteria, anaerobic gram‐positive cocci, fusiform bacteria, curved rods, and spirochetes appeared when the rats were 2 to 4 weeks old. Yeasts were slower in colonizing the tract than any other organism. Dramatic changes occurred in the microflora of rats 2 to 4 weeks of age. There was a time lag between the changes in enterococcal and coliform populations. The enterococcal population was depressed over a period from 2 to 6 weeks of age. Bifidobacteria showed a larger population at 4 to 9 weeks than at any other age. The microflora of the stomach was the same as that of the small intestine, with some exceptions. It differed markedly from that of the cecum. The ratio of total aerobic count to anaerobic count gradually increased in the stomach, but decreased in the cecum, with advance in age. The microorganisms distributed in the tract could be divided roughly into 3 types. The population of each organism, except spirochetes, in the cecal wall was approximately 1/1,000 of that in the cecal contents. One of the 2 types of spirochetes was found only in the cecal wall and in a high incidence, forming a large population. In rats starved for 48 hr, coliforms, Proteus spp., anaerobic gram‐positive cocci, Clostridia, and some bacteroidaceae showed an increase in population in the cecum, but lactobacilli, veillonellae, and spirochetes decreased. The major organisms cultured from the heat‐treated feces were fusiform and curved bacteria, some members of Bacillus, minor anaerobic cocci, and straight rods.