Interactions between Glycopeptides and β-Lactams against Isogenic Pairs of Teicoplanin-Susceptible and -Resistant Strains of Staphylococcus haemolyticus

Four isogenic derivatives with stably increased glycopeptide MICs (all become resistant to teicoplanin) were obtained from four glycopeptide-susceptible clinical isolates of Staphylococcus haemolyticus. All strains were extensively analyzed and compared for a number of distinctive features. In particular, the results provided insights into the puzzling issue of antistaphylococcal interactions between glycopeptides and beta-lactams, especially the paradox of double zones around beta-lactam disks and the relationships between autolysis rate and type of interaction.