RT Journal Article SR Electronic T1 The evolving epidemiology of Clostridium difficile infection in Canadian hospitals during a postepidemic period (2009–2015) JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP E758 OP E765 DO 10.1503/cmaj.180013 VO 190 IS 25 A1 Kevin C. Katz A1 George R. Golding A1 Kelly Baekyung Choi A1 Linda Pelude A1 Kanchana R. Amaratunga A1 Monica Taljaard A1 Stephanie Alexandre A1 Jun Chen Collet A1 Ian Davis A1 Tim Du A1 Gerald A. Evans A1 Charles Frenette A1 Denise Gravel A1 Susy Hota A1 Pamela Kibsey A1 Joanne M. Langley A1 Bonita E. Lee A1 Camille Lemieux A1 Yves Longtin A1 Dominik Mertz A1 Lorraine Maze Dit Mieusement A1 Jessica Minion A1 Dorothy L. Moore A1 Michael R. Mulvey A1 Susan Richardson A1 Michelle Science A1 Andrew E. Simor A1 Paula Stagg A1 Kathryn N. Suh A1 Geoffrey Taylor A1 Alice Wong A1 Nisha Thampi A1 , YR 2018 UL http://www.cmaj.ca/content/190/25/E758.abstract AB Background: The clinical and molecular epidemiology of health care–associated Clostridium difficile infection in nonepidemic settings across Canada has evolved since the first report of the virulent North American pulsed-field gel electrophoresis type 1 (NAP1) strain more than 15 years ago. The objective of this national, multicentre study was to describe the evolving epidemiology and molecular characteristics of health care–associated C. difficile infection in Canada during a post-NAP1-epidemic period, particularly patient outcomes associated with the NAP1 strain.Methods: Adult inpatients with C. difficile infection were prospectively identified, using a standard definition, between 2009 and 2015 through the Canadian Nosocomial Infection Surveillance Program (CNISP), a network of 64 acute care hospitals. Patient demographic characteristics, severity of infection and outcomes were reviewed. Molecular testing was performed on isolates, and strain types were analyzed against outcomes and epidemiologic trends.Results: Over a 7-year period, 20 623 adult patients admitted to hospital with health care–associated C. difficile infection were reported to CNISP, and microbiological data were available for 2690 patients. From 2009 to 2015, the national rate of health care–associated C. difficile infection decreased from 5.9 to 4.3 per 10 000 patient-days. NAP1 remained the dominant strain type, but infection with this strain has significantly decreased over time, followed by an increasing trend of infection with NAP4 and NAP11 strains. The NAP1 strain was significantly associated with a higher rate of death attributable to C. difficile infection compared with non-NAP1 strains (odds ratio 1.91, 95% confidence interval [CI] 1.29–2.82). Isolates were universally susceptible to metronidazole; one was nonsusceptible to vancomycin. The proportion of NAP1 strains within individual centres predicted their rates of health care–associated C. difficile infection; for every 10% increase in the proportion of NAP1 strains, the rate of health care–associated C. difficile infection increased by 3.3% (95% CI 1.7%–4.9%).Interpretation: Rates of health care–associated C. difficile infection have decreased across Canada. In nonepidemic settings, NAP4 has emerged as a common strain type, but NAP1, although decreasing, continues to be the predominant circulating strain and remains significantly associated with higher attributable mortality.