Comparative activity of ampicillin, amoxycillin, amoxycillin/clavulanate and cefotaxime against 189 penicillin-susceptible and -resistant pneumococci.

Agar dilution and E-test MICs of penicillin G, ampicillin, amoxycillin, amoxycillin/clavulanate and cefotaxime were determined against 189 pneumococci. Addition of clavulanate did not influence amoxycillin MICs, MIC50/MIC90 (mg/L) for penicillin G, ampicillin, amoxycillin and cefotaxime were: Penicillin susceptible strains (62): 0.03/0.03; 0.03/0.06; 0.015/0.03; 0.015/0.06. Penicillin intermediate strains (69): 0.25/1.0; 0.25/4.0; 0.125/1.0; 0.125/1.0. Penicillin resistant strains (58): 2.0/4.0; 4.0/4.0; 1.0/2.0; 1.0/2.0. E-test MICs correlated well with those obtained by agar dilution.