Effect of Terramycin on Fecal Microflora of Rats. I. Interrelation of Diet and Terramycin.

A study was made of changes in fecal microflora of albino rats engendered by changes in composition of diet, and by incorporation of terramycin in the 3 diets employed. The data were statistically analyzed as to ration effect, drug effect, interaction between ration and diet and reproducibility of experiments. 2. Diets per se, showed little or no effect in modifying the counts of total anaerobes and aerobes, L. acidophilus, or fecal streptococci. Nor was there a statistically significant interaction between terramycin and diet in these groups of organisms. Terramycin caused significant reductions of anaerobes, aerobes, and L. acidophilus and a marked increase of fecal streptococci regardless of ration. 3. The use of tergitol-7-agar containing T.T.C. was described for enumeration of E. coli in feces. The counts of E. coli were not affected by diet or terramycin per se, but a high degree of interaction between diet and terramycin obtained. The action of terramycin on the E. coli count was dependent on the type of ration fed, especially as evidenced by significant differences between terramycin supplemented high carbohydrate low protein ration and terramycin supplemented basal ration. 4. The high carbohydrate low protein diet resulted in a much lower count of Proteus spp. than either of the other 2 rations. Supplementation of all rations with terramycin resulted in a marked increase in numbers of Proteus spp. It was especially noted that the effect of terramycin was independent of the ration fed in this case.