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

In an in 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 of Staphylococcus aureus showed an MIC > or = 4 mg/l and 100 strains of S. aureus showed an MIC > or = 256 mg/l. In addition, 25 strains of coagulase-negative staphylococci resistant to erythromycin at an MIC of > or = 4 mg/l were investigated. At an MIC of 2 mg/l 57% of the erythromycin-resistant strains of S. 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 active in vitro against more than 50% of erythromycin-resistant strains of S. aureus. This drug is also more active than roxithromycin and clarithromycin against erythromycin-resistant S. aureus.