Multidrug-resistant Escherichia coli isolated from free-range chickens in the Caatinga biome

Abstract Antimicrobial resistant Escherichia coli is a global health challenge in a One Health perspective. However, data on its emergence in the Caatinga biome are limited. This biome is exclusive to the Brazilian Northeast and offers unique epidemiological conditions that can influence the occurrence of infectious diseases and antimicrobial resistance. In this study, we assessed the carriage proportion, the antimicrobial susceptibility, and the population structure of cephalosporin-resistant E. coli in 300 cloacal swab samples of free-range chickens from three Brazilian states covered by Caatinga biome. The results showed that 44 (14.7%) samples were positive for cephalosporin-resistant E. coli, and Paraíba (PB) state had the highest frequency of isolates (68.2%). Genes encoding CTX-M or AmpC enzymes were identified in 30 (68.2%) and eight isolates (18.2%), respectively, comprising 31 E. coli. Overall, molecular typing by XbaI-PFGE revealed four clusters from two properties of the PB state composed by ESBL- and AmpC-producing E. coli carrying blaCTX−M−1−like and blaMIR−1/ACT−1 genes and belonging to different phylogenetic groups. There is a need for controlling antimicrobial resistance taking into account the genetic diversity of the strains and their implications for animal and public health, especially in free-range chickens reared in the Brazilian Caatinga biome.