RESUMO
In this study we characterized the genetic environment of blaCTX-M and blaCMY-2 genes carried by 46 Escherichia coli isolates obtained from 20 chicken carcasses produced by five different brands in Brazil, including exporters and antibiotic-free-certified producers, purchased between 2010 and 2014. Similar plasmids characterized according to size and incompatibility group (Inc) were identified in E. coli belonging to different MLST-ST collected, regardless of carcass brand or production system. Hybridization assays with transconjugant strains revealed that blaCMY-2 gene (n = 19) was located on 85 kb plasmids of IncB/O, IncI1, IncFIB, or nontypeable groups. blaCTX-M-8 (n = 9) was located on 90 kb IncI1 plasmids. blaCTX-M-2 (n = 14) was inserted in class 1 integrons and conjugated only by one isolate in a 125 kb IncP plasmid. blaCTX-M-15 (n = 1), rarely described in isolates from food-producing animals in South America, was characterized by whole genome sequencing of transconjugant; the gene was carried in a 49.3 kb IncX1 plasmid. Sequencing of bla gene-flanking regions indicated the association of these genes with previously described insertion sequences. These results suggest that conserved genetic environments are related to ESBL and pAmpC genes in the Brazilian chicken production chain.