The effect of antibacterial drugs on the fecal flora of mice

Abstract

As reported in preceding papers, the NCS colony of Swiss mice developed at the Rockefeller Institute is characterized by a fecal flora poor in enterococci and Gram-negative bacilli, but very rich in lactobacilli (1, 2). This fecal flora naturally changes when newborn NCS animals are exposed to ordinary mice. Unexpectedly however, it remains essentially unchanged when adult NCS mice are placed in a room containing contaminated animals, provided the NCS mice are fed an adequate diet and are not subjected to physiological disturbances. In contrast, as will be shown in the present paper, the composition of the flora changes profoundly when the animals are treated with certain antibacterial drugs. Furthermore, the nutritional regimen markedly affects the extent and duration of the changes in the fecal flora induced by these drugs. Similar effects, although quantitatively less striking, have been observed with other Swiss mice possessing an intestinal flora more complex than that of NCS animals. © 1963, Rockefeller University Press., All rights reserved.