Antimicrobial activity of josamycin against erythromycin-resistant staphylococci as compared to roxythromycin and clarithromycin

In anin vitro study 246 clinical isolates of erythromycin-resistant staphylococci from six hospitals in Austria were investigated for susceptibility to josamycin and other, newer macrolide antibiotics, e.g. roxithromycin and clarithromycin. 71 strains ofStaphylococcus aureus showed an MIC ≥ 4 mg/l and 100 strains ofS. aureus showed an MIC ≥ 256 mg/l. In addition, 25 strains of coagulase-negative staphylococci resistant to erythromycin at an MIC of ≥ 4 mg/l were investigated. At an MIC of 2 mg/l 57% of the erythromycin-resistant strains ofS. aureus were inhibited by josamycin, 25% by clarithromycin and 11.6% by roxithromycin. At an MIC of 2 mg/l 13.3% of erythromycin-resistant coagulase-negative staphylococci were inhibited by josamycin, 10.7% by clarithromycin and 9.3% by roxithromycin. This study suggests that josamycin is still activein vitro against more than 50% of erythromycin-resistant strains ofS. aureus. This drug is also more active than roxithromycin and clarithromycin against erythromycin-resistantS. aureus.