No abstract

The macrolide antibiotics josamycin and rosamicin were compared in vitro with erythromycin for activity against Staphylococcus aureus, S. epidermidis , and enterococci and with clindamycin for activity against a variety of anaerobic organisms. Rosamicin and erythromycin were similar in activity and superior to josamycin against aerobic cocci. Most isolates of S. aureus (96%), S. epidermidis (79%), and the enterococci (87%) were inhibited by 1.56 μg of either of the new macrolide compounds per ml. Clindamycin was the most active compound against the anaerobic organisms.

The efficacies of lincomycin (L) and spectinomycin (S), alone and in various combinations (L/S), were determined against Escherichia coli (EC) and Staphylococcus aureus (SA) of avian origin, both in vitro and in vivo. L contributed significantly to L/S activity against SA, while S contributed significantly to L/S activity against EC, and L/S (2.5 mg L + 5.0 mg S) was more effective than either L or S against SA and EC. The suggested optimum dose for controlling early chick mortality caused by SA and EC is 2.5/5.0 mg of L/S per chick.