Factors influencing the inactivation of aminoglycosides by beta-lactams.

Aminoglycosides and beta-lactam antibiotics were tested alone and in combination, via bioassay, in the presence of pH buffers at 6.5, 7.5 and 8.5; human serum; MgCl2 and CaCl2; clavulanic acid and beta-lactamase. Results show: inactivation of gentamicin, tobramycin, sisomicin and netilmicin is influenced by pH; clavulanic acid can inactivate gentamicin and tobramycin; and inactivation is influenced by salt concentration and constituents.