In vitro activity of MK-0366 against clinical urinary pathogens including gentamicin-resistant Pseudomonas aeruginosa.

MK-0366, a new derivative of nalidixic acid, was tested against 250 urinary pathogens including Escherichia coli, Serratia marcescens, and Pseudomonas aeruginosa. This new agent was more active than any of the other antibiotics tested, which included carbenicillin, ampicillin, cephalexin, tetracycline, trimethoprim, trimethoprim-sulfamethoxazole, and nalidixic acid. Gentamicin-resistant P. aeruginosa were highly sensitive to MK-0366, with a 90% minimal inhibitory concentration of 0.8 microgram/ml. Serratia strains were the most resistant organisms, with a 90% minimal inhibitory concentration of 3.1 micrograms/ml. These results suggest that clinical trials should be designed to investigate the clinical usefulness of this new drug in urinary infections.