The effect of calcium on the antibacterial activity of gentamicin in urine.

the influence of various concentrations of calcium on the antibacterial activity of gentamicin in urine on 10 strains of E. coli and 10 strains of P. aeruginosa was studied in vitro. It was found that calcium has a strong antagonistic effect on gentamicin activity, particularly with regard to P. aeruginosa. This effect is greatly reduced when gentamicin concentrations are increased to levels higher than those obtained in urine under conventional treatment schedules.