Staphylococcus meticilina-resistentes de origem animal: detecção de variantes do gene mec e seus reguladores

Abstract

Staphylococcus spp. is the most important pathogen causing contagious bovine mastitis, presenting a high level of antimicrobial resistance, especially to beta-lactams, which favors its persistence in the herd. In order to characterize strains of Staphylococcus spp. from a dairy farm located in the South-Fluminenese region of the state of Rio de Janeiro, samples of milk, milking, professionals and dogs and cats were collected in the milking environment of a farm during the four seasons of the year in the period of 2014 and 2015. A total of 321 samples were obtained, resulting in 248 isolates of Staphylococcus spp., and Staphylococcus aureus was the most prevalent specie, 64,1% (150/234). Phenogenotypic tests of resistance to beta-lactams revealed high percentages of phenotypic resistance to penicillin, indicating the production of beta-lactamases as the predominant mechanism of resistance. Only coagulase negative Staphylococcus amplified the mec gene (mecA, mecA variant and mecC). Three strains amplified the classic mecA gene. In two, it was possible to amplify the variant of the mecA gene previously reported by our study group. Analyzing the correlation between the cefoxitin and oxacillin markers with the detection of the mec gene, was observed that cefoxitin demonstrated greater discriminatory power than oxacillin in strains of bovine origin in the national territory, however this correlation was not observed in the strains of Iowa State University collection, in which oxacillin showed greater predictive power. The primers for the detection of the regulatory system of mec gene, developed in this study, classified only the isolates that amplified the classic mecA gene, which carried the SCCmec type V, and the primers elaborated for the identification of the regions adjacent to mecA variant gene, not added new information, and it is not possible to identify the regulatory system of the mec gene in variant mecA isolates. High genetic heterogenity and consequent low clonal correlation was observed in strains of S. sciuri mec positive submitted to PFGE technique.