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To the Editor: Medalla et al. reported increased incidence of antimicrobial-resistant human infections with nontyphoidal Salmonella in the United States during 2004–2016 (1). When comparing incidence in 2004–2008 with that in 2015–2016, Bayesian hierarchical modeling estimated a 40% increase in the annual incidence of Salmonella infections with clinically important resistance (resistance to ampicillin or ceftriaxone or nonsusceptibility to ciprofloxacin). Most of the reported increases were attributed to serotypes I 4,,12:i:- and Enteritidis.
The US study used data from Laboratory-Based Enteric Disease Surveillance (https://www.cdc.gov/salmonella/reportspubs/surveillance.html) and the National Antimicrobial Resistance Monitoring System (https://www.cdc.gov/narms/index.html). The corresponding programs in Canada are the National Enteric Surveillance Program and the Canadian Integrated Program for Antimicrobial Resistance Surveillance (2,3). We used descriptive and univariable analyses without modeling for a preliminary comparison of data from these programs.
In Canada, yearly incidence (per 100,000 population) of human nontyphoidal Salmonella infections increased by 17% from 2004–2008 (median 18 cases) to 2015–2016 (median 21 cases). For nontyphoidal Salmonella (n = 20,665 isolates), resistance to ampicillin or ceftriaxone did not change substantially from 2004–2008 (ampicillin 15%; ceftriaxone 4%) to 2015–2016 (ampicillin 13%; ceftriaxone 5%). However, ciprofloxacin nonsusceptibility in nontyphoidal Salmonella increased from 7% in 2004–2008 to 15% in 2015–2016. For Salmonella Enteritidis (n = 6,694 isolates), resistance to ampicillin and ceftriaxone was uncommon (ampicillin 3%; ceftriaxone <1% for both 2004–2008 and 2015–2016). However, ciprofloxacin nonsusceptibility increased from 15% in 2004–2008 to 24% in 2015–2016. For Salmonella I 4, ,12:i;- (n = 686 isolates), ampicillin resistance increased from 20% in 2004–2008 to 53% in 2015–2016, but ceftriaxone resistance decreased from 8% to 3%. Thus, increases were observed in both the United States and Canada for ciprofloxacin nonsusceptibility in Salmonella Enteritidis and for ampicillin resistance in Salmonella I 4, ,12:i;-. Future modeling of surveillance data, enhanced by genomic analysis, will provide a more comprehensive comparison of findings for these countries.
Members of the CIPARS Provincial Partnership who contributed data: David C. Alexander (Cadham Provincial Laboratory, Winnipeg, MB, Canada), Vanessa Allen (Public Health Ontario Laboratories, Toronto, ON, Canada), Sameh El Bailey (Horizon Health Network, Saint John, NB, Canada), Sadjia Bekal (Laboratoire de Santé Publique du Québec, Sainte-Anne-de-Bellevue, QC, Canada), Greg J. German (Queen Elizabeth Hospital, Charlottetown, PEI, Canada), David Haldane (Queen Elizabeth II Health Sciences Centre, Halifax, NS, Canada), Linda Hoang (British Columbia Centre for Disease Control, Vancouver, BC, Canada), Linda Chui (Alberta Precision Laboratories-Provincial Laboratory for Public Health, Edmonton, AB, Canada), Jessica Minion (Roy Romanow Provincial Laboratory, Regina, SK, Canada), and George Zahariadis (Newfoundland and Labrador Public Health and Microbiology Laboratory, St. John’s, NL, Canada)
Author affiliations: Public Health Agency of Canada, Winnipeg, Manitoba, Canada (A. Bharat, M.R. Mulvey); Public Health Agency of Canada, Guelph, Ontario, Canada (C.P. Murphy, S. Hussain, C.A. Carson, R.J. Reid-Smith)
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