Background. The occurrence of community-associated infections due to extended-spectrum β-lactamase (ESBL)-producing Escherichia coli has been recognized as a major clinical problem in Europe and other regions. Methods. We conducted a prospective observational study to examine the occurrence of community-associated infections due to ESBL-producing E. coli at centers in the United States. Five academic and community hospitals and their affiliated clinics participated in this study in 2009 and 2010. Sites of acquisition of the organisms (community-associated or healthcare-associated), risk factors, and clinical outcome were investigated. Screening for the global epidemic sequence type (ST) 131 and determination of the ESBL types was conducted by polymerase chain reaction and sequencing. Results. Of the 291 patients infected or colonized with ESBL-producing E. coli as outpatients or within 48 hours of hospitalization, 107 (36.8%) had community-associated infection (81.5% of which represented urinary tract infection), while the remainder had healthcare-associated infection. Independent risk factors for healthcare-associated infection over community-associated infection were the presence of cardiovascular disease, chronic renal failure, dementia, solid organ malignancy, and hospitalization within the previous 12 months. Of the community-associated infections, 54.2% were caused by the globally epidemic ST131 strain, and 91.3% of the isolates produced CTX-M-type ESBL. Conclusions. A substantial portion of community-onset, ESBL-producing E. coli infections now occur among patients without discernible healthcare-associated risk factors in the United States. This epidemiologic shift has implications for the empiric management of community-associated infection when involvement of E. coli is suspected.

The Clinical and Laboratory Standards Institute (CLSI) Subcommittee on Antimicrobial Susceptibility Testing (AST SC) is a volunteer-led, multidisciplinary consensus body that develops and publishes standards and guidelines (among other products) for antimicrobial susceptibility testing (AST) methods and results interpretation in the United States and internationally. The Subcommittee (SC) meets face-to-face twice yearly, and its working groups (WGs) are active throughout the year via teleconferences. All meetings are open to the public. Participants include clinical microbiologists, infectious disease (ID) pharmacists, and infectious disease physicians representing the health care professions, government, and industry. Individuals who work for a company with a primary financial dependency on drug sales cannot serve as voting members, and well-defined conflict of interest polices are in place. In addition to developing and updating susceptibility breakpoints, the SC develops and validates new testing methods, provides guidance on how results should be interpreted and applied, sets quality control ranges, and educates users through seminars, symposia, and webinars. Based on its work, the SC publishes print and electronic standards and guidelines, including an annual update, the Performance Standards for Antimicrobial Susceptibility Testing (M100). This commentary will describe the background, organization, functions, and operational processes of the AST SC.

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