In vitro activity of chloropolysporin-C, a new glycopeptide-group antibiotic, on Clostridium perfringens isolates and its in vivo activity against C. perfringens and other intestinal microflora of the caeca of broiler chickens.

The influence of chloropolysporin-C, a new glycopeptide antibiotic, on in vitro activity of Clostridium perfringens isolates and its effects on the intestinal microflora of broiler chickens was examined. The in vitro sensitivity of 88 isolates of C perfringens to four antimicrobial agents, including chloropolysporin-C, was tested by an agar dilution method. The antibiotics used all had minimum inhibitory concentration levels of 6·25 µ g ml –1 or less against this organism. Changes were examined in the intestinal microflora of broiler chickens fed a diet containing chloropolysporin-C to obtain basic data on the mechanisms by which the antibiotic aided livestock production. No clinical findings were recognised in chickens tested during the period of antibiotic administration. A decrease in viable cells of the clostridia was the principal response recognised during the period of drug administration in feed. Among the other microflora, chloropolysporin-C led to a significant response among Grampositive bacteria, but no changes in the total bacterial count.