Effect of Cessation of Ceftiofur and Substitution with Lincomycin-Spectinomycin on Extended-Spectrum-β-Lactamase/AmpC Genes and Multidrug Resistance in Escherichia coli from a Canadian Broiler Production Pyramid.

Ceftiofur, a third-generation cephalosporin antimicrobial, was used in Canadian hatcheries for many years to prevent early mortality in chicks, leading to a high prevalence of cephalosporin resistance in in chickens. Preventive use of ceftiofur in hatcheries ceased in 2014. We examined the effect of ceftiofur cessation ( = 40 flocks with ceftiofur and  = 28 flocks without antimicrobial at hatchery) and its replacement with an antimicrobial combination, lincomycin-spectinomycin ( = 32), at the hatchery on the proportion of samples with positive for extended-spectrum-β-lactamase (ESBL) and AmpC β-lactamase-related genes, and on the multidrug resistance profiles of ESBL/AmpC-positive in broilers and their associated breeders ( = 46 samples), at 1 year postcessation. For indicator from nonenriched media, a significant decrease postcessation in the proportion of samples harboring isolates positive for and/or was observed. In contrast, following enrichment in medium containing ceftriaxone (1 mg/liter) to facilitate recovery of ESBL/AmpC β-lactamase-producing colonies, both pre- and postcessation, 99% of the samples harbored positive for or Among the 15 tested antimicrobial agents, flocks receiving lincomycin-spectinomycin after cessation of ceftiofur showed a significantly greater nonsusceptibility to aminoglycosides, folate inhibitors, phenicols, and tetracyclines and a greater proportion of possible extensively drug-resistant than those receiving ceftiofur or no antimicrobial at hatchery. This study clearly demonstrates an initial decrease in ESBL/AmpC-positive following the cessation of ceftiofur in the hatchery but an increase in antimicrobial non-β-lactam resistance of ESBL/AmpC-positive following replacement with lincomycin-spectinomycin. Antimicrobial resistance is a global problem. The antimicrobial ceftiofur has been used worldwide for disease prevention in poultry production, resulting in a greatly increased resistance to this antimicrobial important in poultry and human medicine. Our study examined the impact of ceftiofur cessation and its replacement with the antimicrobial combination lincomycin-spectinomycin, a common practice in the industry. Our study demonstrated a decrease in ceftiofur resistance after the cessation of ceftiofur use, although the resistance genes remain ubiquitous in all phases of poultry production, showing that poultry remains a reservoir for ceftiofur resistance and requiring continued vigilance. We also observed a decrease in multidrug resistance involving different antimicrobial classes after cessation of ceftiofur but an increase following use of lincomycin-spectinomycin, indicating that this antimicrobial use should be questioned. Reduced resistance to ceftiofur in poultry may translate to better treatment efficacy, decreased morbidity/mortality, and enhanced food safety for humans.