Study finds low rates of E. coli susceptibility to ampicillin, cotrimoxazole, and cefuroxime.


CHICAGO—An international survey of uropathogens isolated from women with uncomplicated UTIs suggests that physicians may need to rethink the antibiotics they use for empiric treatment.

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Given the pattern of antibiotic resistance among Escherichia coli—which was isolated from three quarters of study participants—investigators concluded that ampicillin, cotrimoxazole, and cefuroxime should not be recommended as empiric therapy for UTIs. Instead, fosfomycin, mecillinam, and nitrofurantoin, which continue to have excellent in vitro efficacy, should be used instead. Study findings were presented here at the recent Interscience Conference on Antimicrobial Agents and Chemotherapy.


Kurt Naber, MD, associate professor of urology at the Technical University of Munich, Germany, and his colleagues prospectively studied the antimicrobial susceptibility of uropathogens in 10 countries. The Antimicrobial Resistance Epidemiological Survey on Cystitis (ARESC) included isolates from women in Austria, Brazil, France, Germany, Hungary, Italy, The Netherlands, Poland, Russia, and Spain. From 2003 through 2006, 73 centers recruited 4,264 eligible women aged 18 to 65 years (mean 38.2 years) with uncomplicated UTIs. Among these subjects, 3,181 (74%) showed positive bacteriuria.


Investigators determined what the minimal inhibitor concentrations of ampicillin, amoxicillin-clavulanate, cefuroxime, nalidixic acid, ciprofloxacin, nitrofurantoin, cotrimoxazole, fosfomycin and mecillinam were for 3,018 isolates.


In the women with positive bacteriuria, pyuria was found in 89% and gross hematuria in 16%. The 3,018 isolates included 2,315 E. coli (76.7 %), 317 other gram-negative bacteria (10.5%), and 386 gram-positive bacteria (12.8%). In the E. coli isolates, drug susceptibility was lowest with ampicillin (45.1%), followed by cotrimoxazole (70.5%), cefuroxime (81.0%), amoxicillin-clavulanate (81.8%), and ciprofloxacin (91.3%). Fosfomycin was the most active agent, with a susceptibility rate of 98.1%. It was followed by mecillinam (susceptibility rate: 95.8%) and nitrofurantoin (susceptibility rate: 95.2%).


Only ciprofloxacin resistance was significantly higher among E. coli strains isolated from women with recurrent UTIs compared with women who did not have recurrent UTIs. Susceptibility patterns differed by country. In Austria, for example, the proportion of susceptible isolates was 100% for fosfomycin, 100% for mecillinam, and 100% for nitrofurantoin. In France, these proportions were 99%, 97%, and 97.3%, respectively. In Spain, the percentage of susceptible isolates was 97.2%, 94.1%, and 94.1%, respectively. In Brazil, the proportions were 97%, 94.6%, and 94.3%, respectively.


“It looks like we need to look at each country individually and examine what is occurring,” Dr. Naber said.