Evaluation of genomic characteristics of Escherichia coli associated with bovine mastitis and the potential utility of alternative antimicrobial methods.

Mastitis is a disease that affects dairy cattle and can be caused by multidrug-resistant Escherichia coli, causing losses to the agricultural sector. To address this, research into new substances with antimicrobial activity is crucial. Thus, the objective of this study was to evaluate the efficacy of extracts of Commiphora leptophloeos, Amburana cearensis, Agave sisalana, and highly soluble polypyrrole (Hs-PPy) against E. coli isolates. Eight E. coli isolates from bovine mastitis and a standard strain were used. The presence of efflux pumps was investigated by ethidium bromide extrusion. Sequencing was performed on the Illumina HiSeq 2500 platform using a 2 × 150 bp library with quality assessed via FastQC and assembly completed using Unicyler. Genome annotation and the identification of resistance and virulence genes were carried out using PROKKA and PanViTa, respectively. Species confirmation as E. coli was achieved via Jspecies and pyANI public genomes from NCBI. Finally, antimicrobial activity was determined by broth microdilution. Among the natural products tested against the isolates only A. cearensis showed antibacterial activity, with a concentration of 12,500 µg/mL, whereas Hs-PPy showed activity at 250 µg/mL. The isolates tested positive for the presence of efflux pump genes, but only 3 isolates expressed the mechanism in vitro. The natural products were not effective in eliminating the bacteria. Hs-PPy was the only compound that demonstrated bactericidal activity against the bacteria, proving to be an alternative for bactericidal action, even in the presence of genes that inhibit its action against a wide variety of compounds.