In vitro effect of pH and glucose concentration on the antibacterial activity of norfloxacin in urine.

The in vitro effect of pH and glucose concentration on the antibacterial activity of norfloxacin in urine was studied. Norfloxacin effectively inhibited the growth of four gram-negative pathogens in urine in vitro at pH values of 6.0, 7.0, and 8.0. The antibacterial activity of norfloxacin in urine was reduced severalfold at pH 6, but minimum inhibitory concentrations (MICs) at this pH remained clinically significant. Glucose at concentrations of 200 mg/dl and 400 mg/dl (simulating glucosuria of diabetes) did not significantly affect the antibacterial activity of norfloxacin when tested against clinical isolates of Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, or Pseudomonas aeruginosa. Norfloxacin appears to be a highly effective antibiotic in vitro under conditions which simulate normal and diabetic states.