[In vitro activity of glycopeptides on 114 coagulase-negative staphylococci: problems with the teicoplanin diffusion test, "alert" parameters indicating need for MIC determination].

The activity of vancomycin (Va) and teicoplanin (Tc) against 114 coagulase-negative staphylococci (CNS) strains was evaluated by disk-diffusion and agar dilution minimal inhibitory concentration (MIC) determination. Results were analysed by species and methicillin-resistance (MR) status. MICs for Va were in the susceptible range (< 4 mg/l) for all strains, with inhibition zone diameters of 17 mm or more in every case. MICs for teicoplanin were 8 or 16 mg/l for 19 CNS strains (including 18 with MR) of which 14 yielded an inhibition zone diameter of 17 mm or more (false susceptibility). Parameters which should lead to MIC determination for Tc regardless of disk diffusion findings include the species (S. haemolyticus), methicillin resistance, Tc zone diameter, and an at least 3 mm difference between the Va and Tc zone diameters.