Phylogenetic characterization of avian pathogenic Escherichia coli strains longitudinally isolated from broiler breeder flocks vaccinated with autogenous vaccine

Abstract

Escherichia coli is the most common bacterial cause of infections in poultry farms. It is known for its genetic heterogenicity that complicates the protection of poultry health through immunoprophylaxis. In farms with continuous problems with colibacillosis, autogenous E. coli vaccine was implemented to the vaccination program instead of commercial vaccines. In this study, we investigated the effect of the autogenous vaccine on E. coli phylogroup diversity on 2 broiler breeder farms with 4 and 5 flocks, respectively. The first flocks on both farms were vaccinated with commercial vaccines, while application of autogenous vaccine was introduced in the second flock on both farms. In total, 113 strains were selected based on the target organs and age of chickens. Targeted organs were the peritoneum, liver, oviduct, and bone marrow, and analyzed strains were isolated from chickens older than 21 wk of age when problems with colibacillosis start emerging. The strains were phylotyped by PCR and allocated to phylogroups A, B1, B2, C, D, E, F or clades I–V. The results showed that autogenous vaccine could significantly affect the phylogroup shift of the strains. On farm A, application of the autogenous vaccine induced significantly lower prevalence ( P = 0.01) of the phylogroups represented in the vaccine among the strains later isolated from the vaccinated flock, while on farm B, the results showed a decrease in the phylogenetic diversity with a dominant prevalence of group B2 despite the vaccine application. The results indicate that implementation of the autogenous vaccine can repress the majority of the strains, but also be unable to eliminate the presence of certain phylogroups, and thus lead to strain shift. Further detailed analyses of multilocus sequence typing and virulence genes will elucidate the pathogenic potential and selection of certain strains, with emphasis on B2 phylogroup.

Virulence and antimicrobial resistance of Escherichia coli isolated from chicken meat, beef, and raw milk

“…Most E. coli strains are belonged to the A and B1 phylogenetic groups. Other authors have reported similar results (Unno et al, 2009;Lagerstrom & Hadly, 2021;Lozica et al, 2021). However, in contrast to the results obtained by Soufi et al (2009), we found in the present study that the number of strains classified in the phylogenetic group D was higher in chicken meat than in beef and raw milk.…”

“…The large number of A and B1 strains recorded in the present study could be explained by the fact that the samples were obtained from healthy animals, and they were probably of faecal origin. These groups are generally associated with commensal strains, whereas in most cases, enteropathogenic strains are assigned to group D and uropathogenic strains are assigned to group B2 (Lozica et al, 2021). We should mention here that enterohemorrhagic E. coli O157H7 belongs to the phylogenic group A.…”

Genomic Analysis of Escherichia coli Longitudinally Isolated from Broiler Breeder Flocks after the Application of an Autogenous Vaccine

“…The antimicrobial susceptibility testing of strains on the Farm A and B showed continuous decrease in resistance, especially on Farm A (unpublished data), which is consistent with the AMR gene results. The results showed the treatment with antimicrobials possibly affected the prevalence of certain E. coli strains, in addition to the effect of autogenous vaccine application [48], although there was no correlation between the antimicrobials used in the flocks and the detected AMR genes (Supplementary Table S3). The implementation of the autogenous vaccine induced genetic homogenization of the isolates [26,48], which increased the selection pressure and alleviated the management of colibacillosis on the investigated farms.…”

“…The results showed the treatment with antimicrobials possibly affected the prevalence of certain E. coli strains, in addition to the effect of autogenous vaccine application [48], although there was no correlation between the antimicrobials used in the flocks and the detected AMR genes (Supplementary Table S3). The implementation of the autogenous vaccine induced genetic homogenization of the isolates [26,48], which increased the selection pressure and alleviated the management of colibacillosis on the investigated farms. The present results correspond to previous studies, which reported that the application of autogenous vaccines alone or in combination with a commercial vaccine serves well as a preventive measure on poultry farms [49][50][51].…”

Isolation, Molecular Characterization, and Antibiotic Resistance of Avian Pathogenic Escherichia coli in Eastern China

“…B1 and C phylogroups were mostly identified among APEC from yolk sac infection (YSI) and septicemia isolates [ 7 ]. The ExPEC, including APEC strains, were grouped under a highly prevalent phylogroup B2 and lower prevalent group D [ 8 , 9 ].…”