Genomic epidemiology of Brucella abortus isolated from cattle in Brazil

Abstract

Bovine brucellosis is a bacterial zoonosis that affects livestock and public health. In Brazil, it is caused mainly by Brucella abortus. The disease causes reproductive clinical signs in cattle, such as abortions and premature births, and nonspecific clinical signs in humans, as fever, arthralgia, night sweats, among others. In humans, the treatment is difficult, and the combination of synergistic antimicrobials for periods of 4 to 6 weeks is preconized. The aims of this study were (1) to perform a systematic review of antimicrobial resistance (AMR) in Brucella spp.; (2) to identify the genetic mechanisms related to AMR in Brucella abortus isolated from cattle in Brazil; (3) to compare the population structure of the genomes of 53 Brazilian B. abortus isolates using eight different genotyping methods; (4) to perform a pan-genome analysis of this species and (5) to describe the identification and complete sequencing of the first strain of Pseudochrobactrum saccharolyticum isolated in Latin America, previously classified as B. abortus. It was possible to identify that Brucella spp. is mainly resistant to rifampicin and aminoglycosides, the mechanisms of genetic resistance in the genus are still poorly understood, and this could be attributed to the high number of hypothetical proteins that remain with their unknown function in this pathogen. In addition, it is essential that the solutions regarding any questions using the implementation of bioinformatics methods always consider the epidemiological context of a isolated strain. Genomics was a fundamental tool to answer several questions related to B. abortus strains from Brazil and enabled the identification of a genus from Brucellaceae family hitherto never found in the country. The intercession between the epidemiological and whole genome sequence information of the strains investigated provided important information on specific nuances of the Brucellaceae family, especially B. abortus, providing a better understanding of this pathogen of worldwide importance.