Mechanism of aminoglycoside resistance in Danish Staphylococcus aureus strains during the years 1979-1987.

A total of 49 gentamicin-resistant strains of Staphylococcus aureus isolated from blood (n = 26) or from other sites (n = 23) during the years 1979 to 1987 were evaluated for the presence of aminoglycoside-inactivating enzymes on the basis of minimum inhibitory concentrations measured by agar dilution as well as inhibition zone diameters determined by disc diffusion. Enzymatic activity was caused by AAC (6′)III/APH (2″) in 45 strains, and by AAC (6′)III/APH (2″)+APH (3′) in four strains. No changes in the distribution of enzymatic activity were observed during the eight years.