Avaliaçãoin vitro da atividade antimicrobiana de biosurfactante complexado com arginina frente a Staphylococcus aureus resistente à meticilina (SARM) e Candida spp. e seu potencial para desagregação de biofilmes em cateteres venosos periférico

Abstract

The spectrum of microbial resistance has been expanding globally, challenging theeffectiveness of antimicrobial therapies and representing a serious threat to public health. Thisissue is further exacerbated by the increasing incidence of biofilm-associated infections.Medical devices, which are widely used in various procedures and treatments, provide afavorable environment for biofilm formation, particularly in catheters, prostheses, and implants.The aim of this study was to evaluate the antimicrobial efficacy of a rhamnolipid complexedwith the amino acid arginine (RLMIX_Arg) against planktonic cells, methicillin-resistantStaphylococcus aureus (MRSA) biofilms, and polymicrobial biofilms formed by MRSA andfluconazole-resistant Candida albicans on polystyrene plates and peripheral venous catheters(PVCs). Additionally, the study assessed the interference of RLMIX_Arg, both in its isolatedform and formulated in a gel, with the biofilm formation process in impregnated catheters.Theminimum inhibitory concentration (MIC) was determined in accordance with CLSI documentsM07-A10 and M23-A3. The assessment of thepharmacological interaction was alsodetermined using the checkerboard methodology. Biofilm formation was assessed throughMTT reduction assays, crystal violet staining, and scanning electron microscopy (SEM).Biofilm formation on catheters was analyzed by counting colony-forming units (CFU/mL).Furthermore, flow cytometry assays were performed to evaluate cell viability and DNAfragmentation in bacterial cells. The MIC of the compound against planktonic MRSA cellsranged from 4 to 16 μg/mL, demonstrating bactericidal activity. Notably, synergy with oxacillinwas observed in 37.5% of the strains, resulting in up to a threefold reduction in oxacillin MIC.For Candida strains, MICs rangedfrom 2 to 13 μg/mL. In addition, concentrations of 64 μg/mLand 80 μg/mL led to asignificant (90%) reduction in biofilm cell viability on polystyrene platesand PVCs, both during the initial formation stage and in mature MRSA biofilms. Forpolymicrobial biofilms formed by MRSA and C. albicans, a concentration of 112 μg/mL(16×MIC) reduced cell viability by approximately 81.8% on plates. Catheters impregnated with RLMIX_Arg at a concentration of 4 mg/mL alone were able to reduce MRSA cell adhesion by29.5%. Prevention of mixed biofilm formation was observed in PVCs impregnated with 10 mg/mL of RLMIX_Arg alone, with approximately 93.8% reduction in cell adhesion. The formulation containing 0.9 μg/mL RLMIX_Arg incorporated into Pluronic F-127 gel provedtobe more effective in preventing mixed biofilms on PVCs, reducing adhesion by about99.1%.Impregnated catheters maintained their antimicrobial effect after 28 days of storage. Themechanism of action against planktonic cells possibly involves membrane damage and concentration-dependent DNA fragmentation. These effects were more pronounced when the compound was combined with oxacillin. The findings indicate that RLMIX_Arg shows potential for application in the prevention of infections associated with MRSA biofilms, both isolated and in combination with C. albicans.