Coumermycin: in vitro activity against 251 clinical isolates of bacteria compared with the activities of eight other antibacterial agents.

The in vitro activity of coumermycin has been compared with those of ampicillin, clindamycin, cloxacillin, doxycycline, erythromycin, netilmicin, penicillin G and vancomycin. A total of 251 clinical isolates of Gram-positive cocci were examined. The minimal inhibitory concentration (MIC) was determined by an agar dilution method. Clindamycin, coumermycin and erythromycin were the most active drugs against Staphylococcus aureus and S. epidermidis on a weight-for-weight basis. All the staphylococcal isolates were inhibited by coumermycin at a concentration of 0.12 mg/l or less. Netilmicin seemed to be somewhat more active against S. epidermidis than against S. aureus. The MICs of vancomycin for the staphylococcal isolates were clustered around 1 mg/l. Streptococcus pneumoniae, S. pyogenes and S. agalactiae were highly susceptible to penicillin G and erythromycin; most isolates were inhibited by 0.03 mg/l or less of either drug. Coumermycin showed poor activity against S. pyogenes, S. agalactiae and enterococci. Most of the S. pneumoniae isolates had also high MICs, although a wide range of sensitivities was found.