Antimicrobial Resistance Phenotype and Genotype of Generic Escherichia coli from Encapsulated Cinnamaldehyde and Citral Fed-Broiler Chicken

This study investigated the effects of in-feed encapsulated cinnamaldehyde (CIN) and citral (CIT) alone or in combination (CIN+CIT) on antimicrobial resistance (AMR) phenotypes and genotypes of E. coli isolated from feces of 6-, 16-, 23-, and 27-days old broiler chickens. The dietary treatments included basal diet (NC), the basal diet supplemented with 55 ppm bacitracin (BAC), 100 encapsulated CIN, CIT, or CIN+CIT. In general, the prevalence of resistance to 10 antimicrobials was lower in the isolates from CIN compared to those from NC or BAC (P < 0.05). The whole genome sequencing analysis of 227 of the 240 isolates detected 26 AMR genes (ARGs) and 19 plasmids but the prevalence of some ARGs and plasmids was lower in E. coli isolated from CIN or CIN+CIT than NC or BAC (P < 0.05). The most prevalent ARGs included tetA (n=108), aac3_Vla (n=91), aadA1 (n=86), bla_CMY-2 (n=78), sul1 (n=77), aph3_lb (n=58), aph6_ld (n=58), and sul2 (n=24). Interestingly, the number of most virulence genes (VGs) increased over time from 6 to 27 days of age (P < 0.05). The prevalence of isolates of serotype O21:H16 was lower in CIN and CIN+CIT while colibacillosis-associated multi-locus sequence types (ST117) were the most prevalent in the isolates from day 23 (P <0.05). A whole genome based phylogenetic tree revealed a close relationship of 25 of 227 isolates to human or broiler extraintestinal pathogenic E. coli. In conclusion, this study indicates that AMR and virulence genotype of E. coli could be affected by encapsulated CIN or CIN+CIT feed supplementation.

Presented at the 2021 Animal Nutrition Conference of Canada. For information on the next edition, click here.