Nosocomial Infections due to Methicillin-Resistant S. aureus (MRSA) at the Kagoshima University Hospital

(2) Susceptibility to Antibiotics

Abstract

Susceptibility to antibiotics of 123 MRSA strains isolated at the Kagoshima University Hospital in 1989 was examined. The results were as follows:
1) Susceptibility of MRSA strains was excellent to VCM, MINO, and RFP, followed by IMP, CLDM, and CPFX. However, most strains were resistant to PCG, MPIPC, ABPC, CET, CMZ, CZON, GM, and AMK.
2) Five strains highly resistant to RFP were isolated. Three of these strains were isolated on the ward for tuberculosis. This suggests easy development of resistance to RFP by MRSA.
3) Differences in susceptibility to antibiotics between coagulase type II and type VII strains were examined. The cumulative percentage of type II strains susceptible to CLDM (MICs<0.5μg/ml) was 15.3%, and that of type VII was 45.2%. Strains resistant to CLDM were more frequently isolated among type II than among type VII strains (p<0.001). A similar relationship between strains and antibiotics was also found with EM and CPEX. On the other hand, the cumulative percentage of type II strains susceptible to AMK (MICs<25 μg/ml) was 89.7%, and that of type VII was 9.7%. Strains resistant to AMK were more frequently isolated among type VII than among type II strains (p<0.001).