Impact of Third-Generation-Cephalosporin Administration in Hatcheries on Fecal Escherichia coli Antimicrobial Resistance in Broilers and Layers

Abstract

ABSTRACTWe investigated the impact of the hatchery practice of administering third-generation cephalosporin (3GC) on the selection and persistence of 3GC-resistantEscherichia coliin poultry. We studied 15 3GC-treated (TB) and 15 non-3GC-treated (NTB) broiler flocks and 12 3GC-treated (TL) and 10 non-3GC-treated (NTL) future layer flocks. Fecal samples from each flock were sampled before arrival on the farm (day 0), on day 2, on day 7, and then twice more.E. coliisolates were isolated on MacConkey agar without antibiotics and screened for 3GC resistance, and any 3GC-resistantE. coliisolates were further analyzed. 3GC-resistantE. coliisolates were found in all 3GC-treated flocks on at least one sampling date. The percentages of 3GC-resistantE. coliisolates were significantly higher in TB (41.5%) than in NTB (19.5%) flocks and in TL (49.5%) than in NTL (24.5%) flocks. In the day 2 samples, more than 80% of theE. colistrains isolated were 3GC resistant. 3GC-resistantE. colistrains were still detected at the end of the follow-up period in 6 out of 27 3GC-treated and 5 out of 25 non-3GC-treated flocks. Many 3GC-resistantE. colistrains were resistant to tetracycline, and there were significant differences in the percentages of resistance to sulfamethoxazole-trimethoprim, streptomycin, or gentamicin between treated and nontreated flocks.blaCTX-MandblaCMY-2were the most frequently detected genes. These results clearly demonstrated that 3GC-resistant strains are introduced early in flocks and that the use of 3GC in hatcheries promotes the selection of 3GC-resistantE. coli. Measures must be implemented to avoid the spread and selection of 3GC-resistant strains.