In-vitro killing activity of combinations of beta-lactam agents with aminoglycosides against penicillin-resistant pneumococci.

Streptococcus pneumoniae has developed resistance to almost every antibacterial agent used in clinical practice, including the most active beta-lactams. This has led to the proposed use of drug combinations. The aim of this study was to determine the efficacy of combinations of beta-lactam agents (cefotaxime or imipenem) with aminoglycosides (gentamicin, netilmicin or amikacin) against pneumococci showing high-level resistance to penicillin and streptomycin and/or kanamycin. All tested combinations were bactericidal and synergic despite the weak concentrations of antibiotics used. Our results suggest that combinations of beta-lactam agents with aminoglycosides may be useful for treating infections by penicillin-resistant pneumococci located outside the central nervous system.