SUSCEPTIBILITIES OF 200 PENICILLIN-SUSCEPTIBLE AND PENICILLIN-RESISTANT PNEUMOCOCCI TO PIPERACILLIN, PIPERACILLIN-TAZOBACTAM, TICARCILLIN, TICARCILLIN-CLAVULANATE, AMPICILLIN, AMPICILLIN-SULBACTAM, CEFTAZIDIME, AND CEFTRIAXONE

MICs of eight beta-lactams (piperacillin, piperacillin-tazobactam, ticarcillin, ticarcillin-clavulanate, ampicillin, ampicillin-sulbactam, ceftazidime, and ceftriaxone) were determined by agar dilution against 64 penicillin-susceptible, 70 intermediately penicillin-resistant, and 66 fully penicillin-resistant pneumococci. The MICs of piperacillin with and without tazobactam for 90% of the susceptible, intermediately resistant, and resistant strains tested (MIC(90)s) were less than or equal to 0.064, 2.0, and 4.0 mu g/ml, respectively. By comparison, those of ampicillin with and without sulbactam were 0.125, 2.0, and 4.0 mu g/ml and those of ceftriaxone were less than or equal to 0.064, 1.0, and 2.0 mu g/ml, respectively. Strains were less susceptible to ticarcillin with and without clavulanate (MIC(90)s, 2.0, 64.0, and 128.0 mu g/ml) and ceftazidime (MIC(90)s, 1.0, 8.0, and 32.0 mu g/ml).