Naslov
Longitudinal study on Escherichia coli gene variability after application of autogenous vaccine in broiler breeder flocks

Autori
Lozica, Liča

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Veterinarski fakultet, Zavod za bolesti peradi s klinikom

Mjesto
Zagreb

Datum
04.05

Godina
2022

Stranica
91

Mentor
Gottstein, Željko

Ključne riječi
Escherichia coli ; APEC ; poultry ; virulence ; autogenous vaccine ; WGS ; MLST ; SNP ; AMR

Sažetak
Escherichia coli (E. coli) is the most common bacterial cause of decreased production and high mortality rates in the poultry industry. Avian pathogenic E. coli (APEC) is one of the extraintestinal E. coli (ExPEC) subpathotypes, characterized by high genetic diversity. Regardless of their diversity, ExPEC strains share many common virulence factors that allow them to colonize tissues outside of the intestine. APEC genetic diversity complicates the efficacy of the immunoprophylaxis programs, which are the foundation of poultry health protection. In this research, 115 E. coli strains were longitudinally isolated from the chicken carcasses diagnosed with colibacillosis. The strains originated from four and five flocks, on Farm A and Farm B, respectively, which are part of the same broiler breeder company. The selected strains originated from the flocks vaccinated with commercial, combination of commercial and autogenous, or solely autogenous vaccines. The strains were sequenced, individually analysed and mutually compared based on the phylogenetic groups, multilocus sequence types (MLST), virulence- associated genes (VAGs), antimicrobial resistance (AMR) genes, and core-genome single-nucleotide polymorphisms (cgSNPs). The aim of this dissertation was to investigate the effect of autogenous vaccines on the genetic heterogeneity of E. coli strains on poultry farms. The results showed that autogenous vaccine application gradually induced lower genetic heterogeneity of the isolates on both farms, based on the prevalence of phylogenetic groups, STs and cgSNP phylogeny. In total, 23 sequence types (STs) were detected, with 52.58% of the isolates belonging to two clonal complexes. Nevertheless, the average number of virulence genes per isolate increased on both farms, while the prevalence of the antimicrobial resistance genes decreased. Out of the highly prevalent STs, ST95, ST390 and ST131 had the highest average number of VAGs per isolate. The overall results of the research confirmed that application of autogenous vaccines affects the genetic heterogeneity and virulence profiles of E. coli.

Izvorni jezik
Engleski

Znanstvena područja
Veterinarska medicina, Biotehnologija u biomedicini (prirodno područje, biomedicina i zdravstvo, biotehničko područje)

POVEZANOST RADA