[Resistance to macrolide antibiotics found in methicillin-resistant Japanese clinical isolates of Staphylococcus aureus in 1996].

Minimum inhibitory concentrations (MICs) of erythromycin, clarithromycin, roxithromycin, oleandomycin, triacetyloleandomycin, azithromycin, josamycin and midecamycin were investigated using 200 strains of methicillin-resistant Staphylococcus aureus (MRSA) clinically isolated in Japan during 1996. The results show that the MRSAs could be classified into five groups according to MIC patterns to various macrolides and that more than 88% of the strains used were highly-resistant to all macrolides tested. It was found that 9.0% of the strains examined showed a unique MIC pattern different to that of macrolide-lincosamide-streptogramin B antibiotic resistance type. This group was found to be highly resistant to 14-membered but susceptible to 16-membered macrolides. The resistance induction by erythromycin or oleandomycin was observed to increase for clarithromycin and roxithromycin resistances in a part of strains used. On the other hand, for azithromycin, such induction was not observed.