Genomic investigation of antimicrobial resistance in Brucella abortus strains isolated from cattle in Brazil

The emergence of resistance to antimicrobials among Brucella spp. has highlighted the need to understand the genetic determinants responsible for these phenotypes. We investigated the gene targets associated with antimicrobial resistance in 53 genomes of B. abortus strains, isolated from cattle in Brazil, with resistance or intermediate susceptibility to antimicrobials. The genetic diversity of the genomes was evaluated using single-nucleotide polymorphism (SNP) differences among the isolates. We compared 18 genes (gyrB, bepD, bepE, norMII, norMI, parC, bepC, folP, gyrA, rpoB, folA, rsmG, marR, parE, mprF, oxyR, bepF, and bepG) previously described as related to antimicrobial resistance in Brucella spp. to those of the reference strain B. abortus 2308, which was susceptible to all tested antimicrobials. Eight genes had nonsynonymous mutations, deletions, or stop codons in at least one of the analyzed genomes. However, we did not observe any association between the genetic polymorphisms in the evaluated genes and the antimicrobial resistance phenotypes observed in the Brazilian analyzed strains (46 intermediate susceptible to rifampicin, 6 resistance to at least one antimicrobial and 1 multidrug resistance).