The Activity of Pipemidic Acid and Piromidic Acid against Escherichia coli In Static Culture and in Conditions Simulating the Treatment of Bacterial Cystitis

The activity of the new pyridopyrimidine compounds, pipemidic and piromidic acids, against Escherichia coli was compared with that of nalidixic acid in vitro . In a static turbidimetric system nalidixic and pipemidic acids were found to be more active than piromidic acid when tested against sensitive E. coli strains, but pipemidic acid was the most active of the three compounds against nalidixic acid-resistant clinical isolates. When tested in an in vitro model designed to mimic the conditions in which bacteria and drug interact in the treatment of bacterial cystitis, all three drugs were found to be able to suppress bacterial growth for long periods, but a high, sustained drug level was necessary in order to prevent the emergence of resistant variants.