MICs of ciprofloxacin and trimethoprim for Escherichia coli: influence of pH, inoculum size and various body fluids.

The influence of pH, inoculum size, human urine and prostatic extract on the MICs of ciprofloxacin and trimethoprim for Escherichia coli was investigated. There was no influence by the bacterial inoculum size within wide ranges on either drug. An increase in pH had a variable influence on the MICs of trimethoprim for E. coli but lowered those of ciprofloxacin considerably. Human prostatic extract increased the trimethoprim MIC for E. coli but lowered those of ciprofloxacin as compared to Mueller Hinton broth. Human urine increased the MICs of both drugs for E. coli.