Limited clinical utility of blood and urine cultures in the treatment of acute pyelonephritis during pregnancy

Objective: The purpose of this study was to determine the utility of urine and blood cultures in the clinical management of pregnant women with acute pyelonephritis. Study Design: Data were pooled from three randomized controlled trials that were conducted at two university-based tertiary care centers and included 391 pregnant women with pyelonephritis. The results of urine and blood cultures were correlated with clinical management decisions, outcome, length of hospital stay, and cost. Results: Results of 98% of urine cultures (382/391) and 99% of blood cultures (388/391) were available for analysis. The most common pathogen isolated was Escherichia coli, which was found in 79% of the urine cultures (300/382) and in 77% of the blood cultures (27/35). Susceptibility testing revealed 46% resistance to ampicillin; 7%, 2%, and 0% resistances to first-, second-, and third-generation cephalosporins, respectively; and 1% resistance to gentamicin. Six percent of the participants (25/391) required changes in antibiotic therapy, most commonly for persistent fever (6/25, 25%). Positive blood culture results directly influenced management by prolonging the duration of hospitalization, with means of 4.6 ± 2.6 hospital days for women with bacteremia and 2.6 ± 1.5 hospital days for women without bacteremia (P< .001) despite similar durations of symptoms. Conclusion: Urine and blood cultures with sensitivity testing had limited utility in the clinical management of pregnant women with pyelonephritis. Decisions to change antibiotic treatment were affected more by clinical course than by culture results. We suggest that elimination of blood and urine cultures might simplify management and result in significant cost savings without compromising patient care. (Am J Obstet Gynecol 2000;182:1437-41.)