Nalidixic Acid and Pivmecillinam for Treatment of Acute Lower Urinary Tract Infections

Abstract

Women, 15-45 years of age, with symptoms of lower urinary tract infection (UTI) were randomly treated with nalidixic acid (1 gx3) or pivmecillinam (200-400 mgx3) for three or seven days, respectively. Therapeutic failure, relapse, or reinfection occurred among 18% of 82 women, even though the isolated strains of gram-negative rods in these patients were susceptible in vitro to the antibiotics used. Therapeutic failure, i.e. no effect or at best only a minor effect on the symptoms, was registered in 10 of 13 cases of UTI caused by Staphylococcus saprophyticus and treated with nalidixic acid, which was consistent with the high minimum inhibitory concentrations (MIC) (128-512 μg/ml) of this antibiotic. S. saprophyticus was isolated in 9 of 12 patients during treatment with nalidixic acid. On the other hand, pivmecillinam therapy was clinically effective in 16 of 18 patients with UTI caused by S. saprophyticus, even though the MIC of mecillinam to these strains was considerably higher (8-64 μg/ml) than that vis-à-vis gram-negative rods. Thus the clinical effect of pivmecillinam was significantly better than that of nalidixic acid in cases of UTI caused by S. saprophyticus. The organism was not isolated from 14 patients receiving pivmecillinam therapy.