Prevalence of antibiotic-resistant uropathogens in obstetric patients with acute pyelonephritis

The purpose of this investigation was to determine the prevalence of antibiotic-resistant uropathogens in 121 pregnant patients hospitalized with acute pyelonephritis. We obtained urine for culture by catheterization and defined a positive culture as greater than 100 colony-forming units per milliliter of urine. We determined bacterial sensitivities with either the Bauer-Kirby disc diffusion test or the Vitek Auto Microbic System. During the 4 years of the study, the prevalence of ampicillin-resistant organisms was 26% (95% confidence interval 18-34%). However, only 4% (95% confidence interval 0-8%) of the uropathogens were resistant to limited-spectrum, first-generation cephalosporins. This observed difference in antibiotic sensitivity was highly significant (P less than .005). Therefore, we conclude that a limited-spectrum cephalosporin is more appropriate than ampicillin for empirical therapy of pyelonephritis in pregnancy.