THE NORMAL INTESTINAL FLORA OF THE PIG. IV. THE EFFECT OF DIETARY SUPPLEMENTS OF PENICILLIN, CHLORTETRACYCLINE OR COPPER SULPHATE ON THE FAECAL FLORA

Abstract

SUMMARY Streptococci, lactobacilli and coli‐aerogenes organisms were isolated from pigs receiving penicillin, chlortetracycline or copper sulphate as dietary supplements. Changes in their numbers, physiological type and sensitivity to the supplements fed are described. Penicillin and chlortetracycline rapidly induced a population resistant to the antibiotic fed, but no changes were detected in numbers or types of organisms isolated. Copper sulphate caused a reduction in the numbers of streptococci and a change of predominant type from non‐lactose‐fermenting to lactose‐fermenting; there was also a change from a flora in which L. acidophilus predominated to one in which L. brevis and L. cellobiosus tended to become dominant.