Population-based laboratory surveillance for Escherichia coli-producing extended-spectrum β-Lactamases: Importance of community isolates with bla_CTX-M genes

A prospective, population-based laboratory surveillance study was conducted to define the epidemiology of extended-spectrum β-lactamase-producing Escherichia coli infections in the Calgary Health Region during the years 2000-2002. The incidence was 5.5 cases per 100,000 population per year. The annualized incidence of 3.9 cases per 100,000 population for January through March was significantly lower than the incidence for the other quarters of the year (6.0 per 100,000 population; PCTX-M genes from the CTX-M-I subgroup and 87 (55%) from the CTX-M-III subgroup. Ciprofloxacin resistance was independently associated with CTX-M-β-lactamases (odds ratio, 14.2; 95% confidence interval, 3.69-54.84). Strains of E. coli with bla_CTX-M genes commonly cause community-onset infections, and women and older patients are at highest risk.