The susceptibility to amoxycillin/clavulanate of Enterobacteriaceae with plasmid-mediated ampicillin resistance: a twelve-year study of strains in one Spanish hospital.

We studied the antibacterial activity of amoxycillin, clavulanic acid and the combination, against 1210 clinical isolates with plasmid-mediated ampicillin resistance, isolated at the Zaragoza Clinical University Hospital during 12 years. MICs were determined by an agar dilution technique with an inoculum of 10(4) cfu per spot. MIC50 values of amoxycillin/clavulanate ranged from 8 to 16 mg/l. The antibacterial activity of amoxycillin/clavulanate did not show any statistically significant variation during the 12-year period.