Análise do potencial antibacteriano e antibiofilme do complexo de rutênio cis-[Ru(phen)2(cys)](PF6) sobre estirpes de Staphylococcus aureus

Abstract

Healthcare-associated infections (HAIs) represent a critical public health challenge, exacerbating morbidity and mortality rates, prolonging hospital stays, and substantially increasing healthcare costs and the risk of permanent disabilities. In this context, increasing microbial resistance drives the investigation of new therapeutic classes, among which ruthenium complexes stand out as promising alternatives to conventional antimicrobials. This study evaluated the antibacterial and antibiofilm activity of the cis-[Ru(phen)2(cys)](PF6) (RuCYS) complex against Staphylococcus aureus ATCC 25923 and Staphylococcus aureus ATCC 700698 (methicillin-resistant S. aureus - MRSA), under photoirradiation conditions with blue light (26 mW/cm2, λirr = 463 nm) and in the absence of photoirradiation. Antimicrobial efficacy was determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). In parallel, biofilms treated with the complex were evaluated through biomass quantification using the crystal violet (CV) staining method, and quantification of viable cells and enumeration of viable cells (CFU), at concentrations ranging from 8 to 512 μg/mL. The results indicated an absence of bacteriostatic or bactericidal activity on planktonic cells within the tested concentration range. However, in biomass quantification assays, S. aureus ATCC 25923 showed a percentage reduction of approximately 77% in the absence of light and 58% under irradiation. For S. aureus ATCC 700698, the reduction reached levels of 87% (without LED) and 75% (with LED). In the analysis quantifying the number of viable cells, the ATCC 25923 strain showed a greater decrease than the ATCC 700698 strain, ranging from 1 to 1.5 log. Therefore, although it did not demonstrate bactericidal action against planktonic cells, the complex exhibits antibiofilm activity with significant reductions in total biomass and number of viable cells in biofilms. There was no significant difference in the complex's action with and without photoirradiation. These findings highlight its potential as an agent in reducing bacterial biofilm formation. Furthermore, as a future perspective, the compound may support the development of new antimicrobials of clinical interest, act synergistically with conventional antibiotics, and contribute to the elucidation of alternative mechanisms for combating biofilms.