MUPIROCIN RESISTANCE IN METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS FROM A VETERANS-HOSPITAL

679 clinical isolates of methicillin-resistant Staphylococcus aureus ( MRSA) which occurred from 1986 and 1992 were retrospectively tested to determine the frequency of mupirocin resistance. With disk agar diffu sion screening, 26 of 679 MRSA had zones of inhibition of < 18 mm usin g a 5 mug mupirocin disk. Minimal inhibitory concentrations (MICs) by agar dilution on the 26 suspect MRSA revealed that 9 were resistant. O f these 9, 1 had a MIC of 6.25, 4 of 12.5, 1 of 25, 1 of 500 and 2 of > 1,000 mug/ml. Although the overall incidence of mupirocin resistance was low in our hospital, 5 of the 9 resistant isolates occurred in 19 92 and may signal a much more serious threat in the future.