Prevalence of Staphylococcus aureus and coagulase-negative staphylococci with decreased sensitivity to glycopeptides as assessed by determination of MICs.

The prevalence of staphylococci with decreased sensitivity to glycopeptides was assessed at a Paris hospital by determination of the MICs. The values obtained using the MIC method were compared to those obtained using the routine disk agar diffusion method. One hundred independently isolated strains were tested including 57 Staphylococcus aureus isolates and 43 coagulase-negative staphylococci (CNS). For all strains vancomycin MICs were less than or equal to 4 mg/l but for 5.3% of the Staphylococcus aureus isolates and 25.6% of the CNS isolates teicoplanin MICs were high (greater than or equal to 8 mg/l). Moreover, teicoplanin MICs did not correlate well with zone sizes. The MIC method is therefore recommended for evaluating the susceptibility of staphylococci to teicoplanin.