Ceftiofur Resistance in Salmonella enterica Serovar Heidelberg from Chicken Meat and Humans, Canada

Abstract

The Canadian Integrated Program for Antimicrobial Resistance Surveillance describes a strong correlation (r = 0.9, p<0.0001) between ceftiofur-resistant Salmonella enterica serovar Heidelberg isolated from retail chicken and incidence of ceftiofur-resistant Salmonella serovar Heidelberg infections in humans across Canada.In Québec, changes of ceftiofur resistance in chicken Salmonella Heidelberg and Escherichia coli isolates appear related to changing levels of ceftiofur use in hatcheries during the study period, from highest to lowest levels before and after a voluntary withdrawal, to increasing levels after reintroduction of use (62% to 7% to 20%, and 34% to 6% to 19%, respectively).These events provide evidence that ceftiofur use in chickens results in extended-spectrum cephalosporin resistance in bacteria from chicken and humans.To ensure the continued effectiveness of extended-spectrum cephalosporins for treating serious infections in humans, multidisciplinary efforts are needed to scrutinize and, where appropriate, limit use of ceftiofur in chicken production in Canada. S almonella enterica serovar Heidelberg ranks amongthe top 3 serovars isolated from persons infected with Salmonella in Canada (1).It is more frequently reported in North America than in other regions of the world (2).Although many Salmonella Heidelberg infections result in mild to moderate illness, the bacterium also causes severe illness with complications such as septicemia, myocarditis, extraintestinal infections, and death (3,4).Salmonella Heidelberg appears more invasive than other gastroenteritis-causing serovars; ≈9% of isolates of this serovar received through the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) during 2003-2005 were recovered from blood samples (5).Treatment with antimicrobial agents may be life-saving in the case of invasive infections.Sources of human Salmonella Heidelberg infection include consumption of poultry or eggs and egg-containing products (6-10).In Canada, Salmonella Heidelberg is commonly isolated from healthy chickens from farm, abattoir, and retail sources (11,12).It also has been isolated, although less frequently, from ground beef, pork, and turkey meat (13-15) and from clinical samples from various animal species (12).Ceftiofur is an extended-spectrum cephalosporin drug approved in Canada for use with numerous label indications in cattle, swine, horses, sheep, turkeys, dogs, and cats.Ceftiofur is also injected in ovo to control Escherichia coli omphalitis in broiler chickens; this use is not an approved label indication.