Epidemic spread of IncI1/pST113 plasmid carrying the Extended-Spectrum Beta-Lactamase (ESBL) blaCTX-M-8 gene in Escherichia coli of Brazilian cattle

Introduction: The prevalence of Extended-Spectrum Beta-Lactamase (ESBL)-producing Enterobacteriaceae is increasing worldwide and the Agri-Food sector acts as a reservoir of clinically relevant ESBL genes. Our study aimed at detecting and characterizing ESBL-producing Enterobacteriaceae responsible for intestinal colonization of Brazilian bovines. Material and methods: ESBL-producing E. coli isolates were recovered from fecal samples of healthy cattle in Northwest Brazil. Antimicrobial susceptibility was determined by disk diffusion. Resistance and virulence genes were identified by PCR and amplicons were sequenced, clonality was assessed by PFGE and MLST, and plasmids were characterized by replicon typing, S1-PFGE and Southern blot hybridizations. Transferability of ESBL genes was assessed by conjugation assay. Results: A total of 40 ESBL-producing E. coli were characterized, which originated from 34/191 animals (17.8 %) and 15/22 farms (68.2 %). The bla(CTX-M-)(8) gene was the most frequent ESBL gene (62.5 %), followed by bla(SHV-2a) (20.0 %), bla(CTX-M-)(2) (10.0 %), and bla(CTX-M-)(15) (7.5 %). The bla(CTX-M-)(8) gene was localized on the IncI1/pST113 plasmid in multiple E. coli sequence types across unrelated animals and farms. Discussion: We report the first characterization and a high prevalence of ESBL-producing E. coli in the beef cattle sector in Brazil, which is mainly supported by the spread of an epidemic IncI1/pST113/bla(CTX-M-)(8) plasmid. Since Brazil is one of the biggest beef meat exporters worldwide, the spread of this ESBL plasmid across other sectors, countries and continents should be considered with attention.