Avaliação in vitro da atividade antibacteriana da menadiona isolada e associada à oxacilina frente a cepas de Staphylococcus aureus: análise em células planctônicas e biofilme

Abstract

Staphylococcus aureus is recognized as one of the main causative agents of bacterial infections, having been responsible for over 1 million deaths in 2019. Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the pathogens most commonly associated with the development of antimicrobial resistance, being considered a priority pathogen for research and development of new drugs by the World Health Organization (WHO). This strain exhibits a higher mortality rate compared to methicillin-sensitive strains (MSSA) and extends the duration of treatment, resulting in significant hospital costs. In this context, drug repurposing emerges as a promising strategy to address the growing challenge of bacterial infections resistant to available treatments. Menadione, known for its anticoagulant properties, is a subject of research in this field. This study aimed to assess the potential of menadione as an antibacterial agent against both MSSA and MRSA strains, investigate its interaction with oxacillin, as well as the mechanisms of action involved, including its biofilm activity. Minimum inhibitory concentration (MIC) assays were conducted using the broth microdilution method, along with minimum bactericidal concentration (MBC) tests. The interaction between menadione and oxacillin was evaluated using the checkerboard technique. Analyses were complemented with scanning electron microscopy. Flow cytometry, fluorescence microscopy, and molecular docking were employed to investigate the mechanism of action. Menadione exhibited antibacterial activity against planktonic cells at concentrations ranging from 2 to 32 μg/mL, with a bacteriostatic effect. When combined with oxacillin, it demonstrated an additive effect of 45% and a synergistic effect of 25% against the tested strains. Menadione also displayed antibiofilm activity at subinhibitory concentrations and effectively combated biofilms with reduced sensitivity to oxacillin alone. Its mechanism of action involves the generation of reactive oxygen species (ROS), resulting in oxidative stress and DNA damage. Its interaction with DNA gyrase and dehydrosqualene synthase enzymes complements its effect. The presence of ascorbic acid reversed its effects. These results highlight the antibacterial and antibiofilm activity of menadione in both sensitive and resistant strains of S. aureus, emphasizing the significance of reactive oxygen species (ROS) as a determining factor for its action. These findings suggest that menadione may be a promising candidate as an adjunct in the treatment of S. aureus infections.