Activity of flumequine against Escherichia coli: in vitro comparison with nalidixic and oxolinic acids

The in vitro activity of the new antibacterial agent, flumequine, against Escherichia coli was compared with those of oxolinic acid and nalidixic acid. As judged by turbidimetric criteria, flumequine was considerably more active than nalidixic acid and slightly less active than oxolinic acid against both nalidixic acid-susceptible and -resistant strains. Resistance to all three drugs could be easily induced in vitro. The comparative efficacy of flumequine, oxolinic acid, and nalidixic acid was also tested in an in vitro model of the treatment of bacterial cystitis. In this system, suppression of bacterial growth was obtained with markedly lower concentrations of flumequine and oxolinic acid than of nalidixic acid, but prevention of the emergence of bacterial populations that exhibited increased resistance to these compounds depended on the maintenance of adequate drug levels.