Oral Antimicrobial Agents for Urinary Tract Infections Due to Enterobacteriales Species

Background Urinary tract infections (UTIs) due to Enterobacteriales continue to pose a challenge because of increasing resistance rate to antimicrobial agents. The aim of this study was to evaluate in vitro susceptibility of oral antimicrobial agents against urinary isolates of Enterobacteriales species in patients with suspected UTIs at Hamilton Health Sciences hospitals in 2016. Methods Positive urine cultures for Enterobacteriales species in all patients 18 years or older with diagnosis of UTIs from 2 acute care hospitals in 2016 were included. Susceptibility rates were calculated for first- and second-line oral antimicrobial agents commonly used to treat UTIs. Results A total of 2773 urinary isolates of Enterobacteriales species were included in the analysis. The rates of susceptibility to nitrofurantoin were 96.3% (1925/1999) and 46.9% (188/401), respectively, for Escherichia coli and Klebsiella pneumoniae . The rates of susceptibility to trimethoprim-sulfamethoxazole and ciprofloxacin were 73.9% (1478/1999) and 84% (337/401), and 72.3% (1446/1999) and 86.3% (346/401), respectively, for E. coli and K. pneumoniae . The rate of E. coli susceptibility to oral cephalosporins was approximately 83%. The proportions of Enterobacteriales isolates that produced extended-spectrum β-lactamases (ESBLs) for E. coli and K. pneumoniae were 11.6% (231/1999) and 11.2% (45/401), respectively. The rates of ESBLs E. coli susceptibility to nitrofurantoin, trimethoprim-sulfamethoxazole, and ciprofloxacin were 91.3% (211/231), 30.3% (70/231), and 16% (37/231), respectively. Conclusions Oral antimicrobial agents have a limited role as empiric treatment of UTIs due to antibiotic-resistant Enterobacteriales species, with the exception of nitrofurantoin for E. coli including ESBL-producing strains. Oral cephalosporins were the second most susceptible agents to E. coli .