Antimicrobial Resistance Among Escherichia coli Urinary Tract Isolates in the United States: A Current View Provided by Electronic Surveillance

Given the numbers of urinary tract infections treated by family physicians and the rapid rise in resistance to traditional first-line therapies, there is a need to monitor antimicrobial resistance regionally and among various patient groups, and to use this information to predict effective empiric therapy. To determine current rates of resistance among Escherichia coli to three commonly prescribed antimicrobials, susceptibility testing results and patient demographic information were gathered via Internet-based electronic surveillance. Among 133,941 urinary tract isolates of E. coli, overall resistance rates were 38.5% for ampicillin, 18.0% for trimethoprim-sulfamethoxazole (TMP-SMX), and 2.2% for ciprofloxacin. Resistance to ampicillin and TMP-SMX was highest among patients aged 18–65 years, whereas resistance to ciprofloxacin was low for all age groups but highest among patients aged >65 years. TMP-SMX resistance was >10% in every region of the United States, ranging from 12.9 to 23.2%. Ciprofloxacin demonstrated the lowest resistance overall (2.2%), as well as low levels of cross-resistance (<2%) with ampicillin and TMP-SMX. Current levels of resistance among E. coli to TMP-SMX suggest that its effectiveness for empiric therapy may be limited in some areas.