Changes in susceptibity of clinical isolates of Staphylococcus aureus to quinolones and other antibacterial agents from 1986 to 1993

We investigated the susceptibity to quinolones and other antimicrobacterial agents of 1,697 Staphylococcus aureus clinical isolates from the Tohoku district collected over the last eight years. The incidence of methicillin-resistant Staphylococcus aureus (MRSA) rose from 25.5% to 49.1% during the eight years. During the above period, susceptibity to ofloxacin remained at almost the same level for methicillin-susceptible Staphylococcus aureus (MSSA). On the other hand MRSA became more resistant year by year, and the MIC₉₀ of ofloxacin against MRSA rose from 0.78 μg/ml in 1986 to 64 μg/ml in 1993. This tendency was observed very frequently among isolates from all institutions and specimens, irrespective of whether they were from in- or out-patients. In was also found that these isolates were generally resistant to quinolones other than ofloxacin.