Salmonella Heidelberg and Salmonella Minnesota in Brazilian broilers: Genomic characterization of third-generation cephalosporin and fluoroquinolone-resistant strains

Salmonella serovars Heidelberg and Minnesota encoding antimicrobial resistance to third-generation cephalosporins and fluoroquinolones are often detected in poultry/poultry meat. We analysed the genomes of 10 Salmonella Heidelberg (SH) and 4 Salmonella Minnesota (SM) from faecal isolates of Brazilian poultry. These featured virulent and multidrug-resistant characteristics, with AmpC beta-lactamase (bla(CMY-2)) predominance (9/14), for all SM (4/4) and some SH (3/10) located on IncC plasmid replicons. IncC carrying bla(CTX-M-2) was only detected among SH (3/10). Mutation in the gyrA/parC genes was present in all SH, whereas SM harboured parC mutation plus qnrB19 on ColRNAI plasmids (3/4). In silico resistance overall corroborated with phenotypic results. Core genome phylogenies showed close clustering and high similarities between the Brazilian and poultry meat/food isolates from Europe, and to human isolates from European countries with documented import of Brazilian poultry meat. Conjugation assays with SM successfully transferred bla(CMY-2), and qnrB19 to an Escherichia coli recipient. The findings reinforce the ongoing antimicrobial resistance acquisition of SH and Minnesota and the risks for disseminating resistant strains and/or mobile elements which may increasingly affect importing countries and the need for controlling AMR in major poultry-exporting countries like Brazil.

Automated summary

Salmonella serovars Heidelberg and Minnesota with resistance to third-generation cephalosporins and fluoroquinolones are frequently found in Brazilian poultry. Genomic analysis revealed the presence of virulent and multidrug-resistant characteristics in these isolates, with AmpC beta-lactamase (bla(CMY-2)) predominance in Salmonella Minnesota (SM) and some Salmonella Heidelberg (SH) on IncC plasmid replicons. The study also identified close genetic similarity between the Brazilian isolates and poultry/food isolates from Europe, as well as human isolates from European countries importing Brazilian poultry meat. Overall, this research highlights the ongoing acquisition and dissemination of antimicrobial resistance in SH and Minnesota, raising concerns for importing countries and emphasizing the need to control AMR in major poultry-exporting countries like Brazil.