Detecção de genes de resistência a fármacos antimicrobianos em genomas de Salmonella Typhimurium e variantes monofásicas

Abstract

Salmonella enterica is a bacterium that causes gastroenteritis in humans, transmitted mainly through the consumption of contaminated food. In recent decades, a new Salmonella serotype (antigenic formula 4,[5],12:i:-) has emerged, which has been demonstrated to be a monophasic variant of the serotype Typhimurium, frequently isolated from foods of animal origin. Isolates of Salmonella 4,[5],12:i:- also show resistance to several antimicrobials. The development of resistant strains is favored by mobile genetic elements, especially plasmids, which demonstrate a central role in the dissemination of antimicrobial resistance genes. The mcr-1 gene has been considered an important marker for resistance to the antibiotic polymyxin/colistin, which is generally the last alternative treatment for multidrug-resistant (MDR) bacteria. This gene has been demonstrated in different enterobacteria in recent years. In the practice of Veterinary Medicine, especially in farm animals, colistin has been administered for decades for metaphylactic, prophylactic and therapeutic purposes for infections caused by enterobacteria. This study analyzed the occurrence of the mcr-1 gene in genomes of S. Typhimurium and its monophasic variants. The methodology consisted of reviews of data from genome banks, including isolates previously sequenced by the research group. The occurrence of several resistance genes was demonstrated in the UFRGS-SA034 strain of S. 1,4,[5],12:i:-. This strain was isolated in 2005 from a sausage sample. Ten genes and/or integrons were detected that confer resistance to eight different classes of antimicrobials, therefore, it was considered to have a multidrug resistance (MDR) profile. The mcr-1 gene, which confers resistance to colistin, was also identified, located on the IncX4 plasmid. In this isolate, other antimicrobial drug resistance genes were also identified, such as qnrB19, sul2, blaTEM-1B, aac(3)-IId, aadA2, dfrA12, aac(6')-Iaa, mdf(A) and tet(B) . These findings demonstrate the effective circulation of S. 4,[5],12:i:- with a multiresistance profile to antibiotics and the occurrence of the gene mcr-1 on a plasmid bacteria isolated from production animals more than 15 years ago. [resumo fornecido pelo autor]