Viable Count of Various Bacteria in the Digestive Tract of Mice

III Changes of Viable Count of Fecal Bacteri with Age

Abstract

Changes of fecal bacterial flora with age were examined in mice. In general, no organism was detected in feces of the 1-day-old mice, while a small number of bacteria were recoverd in a few mice aged 3 days. Enteric bacteria reached a constant population around 3 weeks after birth (10^4-6/g), showing a maximum count around 1 week after birth (10⁹/g) . A constant population of streptococci or staphylococci was established around 1 week after birth (10^4-6/g) . The population of lactobacilli or bacteroides reached the maximum level in mice aged 2 to 3 weeks (10⁹/g) . Spores of aerobic rods were first recovered in 3-week-old mice (10³/g), and considered as transient organisms fed with diet. Although a small number of yeasts were detected in a few mice within 2 weeks after birth, a constant level of the population was established 3 weeks after birth (10^6-7/g) . Bifidus and clostridia were, detected in a few mice. At present, there was no evidence on the difference among mouse strains in the development of fecal flora.