Utility of urine and blood cultures in pyelonephritis.

Abstract

To determine how often the results of urine and blood cultures led to changes in antibiotic therapy for patients discharged from the hospital with the diagnosis of pyelonephritis. A retrospective chart review was performed of consecutively admitted patients, 10-90 years old, with an ICD-9 discharge diagnosis of acute pyelonephritis. All patients were admitted to a university-based, tertiary care center and a large HMO medical center from 1993 to 1994. The association of urine and blood culture results with a change in antibiotic therapy was assessed. Of the 194 patients who met inclusion criteria, 189 (97%) had urine cultures obtained at the time of admission and 139 (71%) had blood cultures obtained. Ampicillin, gentamicin, or both were given as initial antibiotics 81% of the time, and isolated organisms from urine or blood were sensitive to the empiric antibiotics 95% of the time. Most (171/189; 90%) urine cultures were positive, but only 9 (5%) of these led to a change in antibiotic therapy. 80% of the urinary pathogens were Escherichia coli, 5% Enterococcus, 5% Proteus, and 4% Klebsiella. Only 40 (29%) of the 139 blood cultures were positive; none prompted a change in antibiotics. There were no cases in which blood and urine cultures grew different pathogens. Urine cultures are useful in directing antibiotic therapy in patients with the discharge diagnosis of acute pyelonephritis and support a change in therapy in 5% of cases. Among the patients in this study, blood cultures results did not lead to changes in antibiotic therapy. These findings warrant prospective, multicenter evaluation.