Boosting Sustainable Innovation in Developing New Antibiotic Adjuvants to Control Biofilm Resistance

Publicações

New insights on antibacterial mode of action of blue-light photoactivated berberine and curcumin-antibiotic combinations against Staphylococcus aureus

Publication . Gonçalves, Ariana S.C.; Fernandes, José R.; Saavedra, Maria José; Guimarães, Nuno M.; Pereira, Cristiana; Simões, Manuel; Borges, Anabela

Antimicrobial photodynamic inactivation (aPDI), using photosensitisers in combination with antibiotics, is a promising multi-target strategy to address antibiotic resistance, particularly in wound infections. This study aimed to elucidate the antibacterial mode of action of combinations of berberine (Ber) or curcumin (Cur) with selected antibiotics (Ber-Ab or Cur-Ab) under blue light irradiation (420 nm) against Staphylococcus aureus, including methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) strains. Multiple physiological parameters were assessed using complementary assays (fluorometry, epifluorescence microscopy, flame emission and atomic absorption spectroscopy, zeta potential, flow cytometry, and the plate agar method) to examine the effect on ROS production, membrane integrity, DNA damage, motility and virulence factors of S. aureus. Results indicated that blue light photoactivated Ber-Ab and Cur-Ab combinations led to substantial ROS generation, even at low concentrations, causing oxidative stress that severely impacted bacterial membrane integrity (approximately 90 % in MRSA and 40 % in MSSA). Membrane destabilization was further confirmed by elevated intercellular potassium release (≈ 2.00 and 2.40 µg/mL in MRSA and MSSA, respectively). Furthermore, significant DNA damage was observed in both strains (≈ 50 %). aPDI treatment with blue light also reduced S. aureus pathogenicity by impairing motility and inhibiting key virulence factors such as proteases, lipases, and gelatinases, all of which play key roles in the infectious process. Overall, Ber-Ab combinations demonstrated the highest efficacy across all parameters tested, highlighting for the first time the multi-target therapeutic potential of this phytochemical-based aPDI strategy to combat antibiotic-resistant S. aureus infections and improve wound infection treatment outcomes.

2025-02-06Artigo científico

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Two cinnamic acid derivatives as inhibitors of Pseudomonas aeruginosa las and pqs quorum-sensing systems: Impact on biofilm formation and virulence factors

Publication . Leitão, Miguel M.; Gonçalves, Ariana S.C.; Sousa, Sérgio F; Borges, Fernanda; Simões, Manuel; Borges, Anabela

Introduction: Quorum sensing (QS) is a bacterial communication mechanism that regulates gene expression, playing a crucial role in various physiological processes. Interfering with this signalling pathway is a promising strategy to control bacterial pathogenicity and virulence. Objectives: This study evaluated the potential of two cinnamic acid derivatives, ferulic and sinapic acids, to inhibit the las and pqs systems in Pseudomonas aeruginosa. Their effects on biofilm architecture, virulence factor production and bacterial motility were also investigated. Methods: Bioreporter strains and bioluminescence-based assays were used to evaluate the modulation of QS-activity by cinnamic acid-type phenolic acids. In addition, in silico docking analysis was performed to validate the binding interactions of the cinnamic acid derivatives with QS-receptors. The biofilm architecture was analysed by optical coherence tomography, and virulence factors production (pyoverdine, pyocyanin, total proteases, lipases, gelatinases and siderophores) and motility were measured by absorbance measurement and plate agar method. Results: Ferulic and sinapic acids at 1000 µg mL-1 inhibited the las and pqs systems by 90 % and 80 %, respectively. The N-3-oxododecanoyl-homoserine lactone production was reduced by 70 % (6.25 µg mL-¹). In silico analysis demonstrated that cinnamic acid derivatives exhibited comparable interactions and higher docking scores than reference ligands and inhibitors. Biofilm thickness decreased from 96 µm to 11 µm, and virulence factors and swarming motility were significantly impaired. The comparable anti-QS activity of cinnamic acid derivatives suggests that the additional methoxy group in sinapic acid does not directly contribute to its anti-QS effect. Conclusion: Ferulic and sinapic acids compromised the biofilm architecture and virulence of P. aeruginosa through QS inhibition.

2025-06-02Artigo científico

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Entidade financiadora

European Commission

Programa de financiamento

HORIZON Coordination and Support Actions

Número da atribuição

101157363