SURVEY OF METHICILLIN RESISTANT Staphylococcus aureus IN SHOWA UNIVERSITY HOSPITAL FROM JULY 1990 TO SEPTEMBER 1992 AND IN VITRO COMBINATION EFFECTS WITH ARBEKACIN AND β-LACTAMS

Abstract

Incidence of Methicillin resistantStaphylococcus aureus (MRSA) in Showa University Hospital from July 1990 to September 1992 was surveyed.S. aureuswas most frequently isolated, and about 50 % was identified as MRSA. The ratio of MRSA inS. aureusisolated each month was 60-80 % from inpatients, and 15-30 % from outpatients. The incidence of MRSA inS. aureuswas 84% and 75%, respectively, in the specimens of urine and pus from inpatients The incidence of MRSA was 18 % and 19 %, respectively, in specimens of pus, or from the respiratory tracts of outpatients.In vitrocombination effects of arbekacin (ABK) and β-lactams against clinical isolates of MRSA (56 strains), whose minimum inhibitory concentcations were over 4μg/ml, were examined. Synergistic and additive effects were observed in, respectively, 82 % and 11 % by ABK plus ampicillin, in 63 % and 0 % by ABK plus fosfomycin, and in 52 % and 25 % by ABK plus clavulanic acid/ticarcillin. No antagonism was observed. Synergism or addition were observed against the MRSA producing β-lactamase. The ABK dose would be decreased by antibiotics combination.