Avaliação in vitro da atividade antimicrobiana do anlodipino em células planctônicas e biofilme de Staphylococcus aureus: determinação do possível mecanismo de ação e sua associação com a oxacilina

Abstract

Antimicrobial resistance is one of the greatest current problems for humanity. Given this scenario, the World Health Organization has listed the main pathogens for which the development of new drugs is a priority. In this list, methicillin-resistant Staphylococcus aureus stands out, considered by the WHO as a high priority pathogen. However, the development of new drugs is a costly and time-consuming process, while the emergence of resistant strains is a fast process. For these reasons, the search for new strategies for research and development of new antimicrobials is fundamental, one of them being drug repositioning. Reports of several classes of non-antibiotic drugs that have demonstrated antimicrobial activity are available in the literature, among them the class of dihydropyridines, one of whose representatives is amlodipine. The present study aims to evaluate the antimicrobial and antibiofilm effects of amlodipine, to assess the type of interaction found with oxacillin, as well as to elucidate the probable mechanism of action involved in its activity against S. aureus. To this end, we used broth microdilution techniques, standardized by the CLSI document M07-A10, checkerboard, to determine the fractional inhibitory concentration (FIC), and scanning electron microscopy to determine the antimicrobial activity of amlodipine. The probable mechanism of action was evaluated by flow cytometry, fluorescence microscopy, and molecular docking techniques. The results obtained showed that amlodipine possesses antimicrobial activity, with minimum inhibitory concentrations (MICs) equivalent to 64 μg/ mL and 128 μg/ mL, and exhibits synergistic-type interactions with oxacillin in more than 50% of the strains used. Furthermore, amlodipine exhibited activity against formed and forming staphylococcal biofilms, with the eradication of these in more than 90% at concentrations above 8 times the MIC. The probable antimicrobial mechanism of action of amlodipine seems to be associated to the binding with DNA gyrase and DNA fragmentation, having as the final effect the death of the microorganism. It can be concluded, therefore, that amlodipine has antimicrobial activity alone and in combination with oxacillin, in planktonic cells and in biofilms.