MONTEREY, CALIF. — Cefazolin remained an effective empiric therapy for antepartum pyelonephritis over the last 14 years, Dr. Soldrea Roberts said at the annual meeting of the Infectious Diseases Society for Obstetrics and Gynecology.
A retrospective study compared data on 136 women with antepartum pyelonephritis who were treated at one institution in two time periods, 1992–1993 and 2004–2006. Records revealed positive cultures in 76%, and 89% of these were caused by gram-negative isolates, found in 47 women in the earlier period and 46 in the later period.
Rates of multidrug resistant organisms causing antepartum pyelonephritis were not significantly different between periods but trended upward, from 32% of isolates in 1992–1993 to 43% in 2004–2006. Multidrug resistance was defined as resistance to at least 3 of an average of 10 antimicrobials tested per isolate.
E. coli caused more than 70% of cases. High rates of ampicillin-resistant E. coli were seen in both time periods—51% of cases in 1992–1993 and 54% of cases in 2004–2006—which confirms the inadequacy of ampicillin for empiric therapy of antepartum pyelonephritis, according to Dr. Roberts of Case Western Reserve University, Cleveland, Ohio, and her associates.
E. coli resistance to trimethoprim-sulfamethoxazole increased significantly from 5% of isolates in the earlier years to 23% in the later years, consistent with trends toward greater trimethoprim-sulfamethoxazole resistance in lower urinary tract infections over this time period. Only 5% of E. coli isolates were resistant to cefazolin in 1992–1993 and all isolates in 2004–2006 were susceptible to cefazolin despite concerns about the emergence of multidrug-resistant gram-negative rods over the past two decades, Dr. Roberts said.
The study was 80% powered to detect a 30% increase in multidrug-resistant isolates between the two time periods.
The likelihood of multidrug resistance was not affected by having a history of antepartum pyelonephritis.
Clinical outcomes did not differ significantly between the two time periods. The average length of hospitalization was 3 days in both periods and did not differ between women with or without multidrug-resistant organisms. Antibiotic regimens were changed during hospitalization in 13% in the earlier period and 11% in the later period. In 1992–1993, 96% of the women delivered at term, compared with 65% in 2004–2006.