Molecular characterisation of multi-drug resistant Escherichia coli of bovine origin

Antimicrobial resistance reported in bacteria of animal origin is considered a major challenge to veterinary public health. In this study, the geno- and phenotypic characterisation Escherichia coli of bovine origin is reported.Twenty bacterial isolates of bovine origin were assessed for their susceptibility to a panel of antimicrobials. Twelve were selected for further study based on their interesting characteristics. In addition efflux pump activity using ethidium bromide (EtdBr) and biofilm formation at diverse temperatures by means of the crystal violet method, were studied.All isolates expressed a multi-drug resistant phenotype, in particular, to fluoroquinolones and tetracyclines which was also confirmed in silico by the presence of acquired resistance markers. Amino acid substitutions in the quinolone resistance-determining regions were identified in all isolates and the presence of several siderophores were also noted. WGS data showed different STs that were not associated with epidemic STs or virulent clonal complexes.Seven isolates were capable of forming biofilms in minimal media with some showing better adaptation at 25°C and others to 37 °C. The capacity to efflux EtdBr was found to be high in 4 isolates and impaired in 4 others.Pathogenicity of 3 selected isolates was assessed in zebrafish embryo infection models. Infection with E. coli CFS0355 and CFS0356 indicated highly pathogenicity after two days.These results highlight the application of NGS technologies combined with phenotypic tests for provide a better understanding of zoonotic E. coli and their adaption to niche environments.