Anti-Staphylococcal Biofilm Effects of a Liposome-Based Formulation Containing Citrus Polyphenols

Abstract

Biofilms are surface-associated microbial communities embedded in a matrix that is almost impenetrable to antibiotics, thus constituting a critical health threat. Biofilm formation on the cornea or ocular devices can lead to serious and difficult-to-treat infections. Nowadays, natural molecules with antimicrobial activity and liposome-based delivery systems are proposed as anti-biofilm candidates. In this study, the anti-biofilm activity of a formulation containing citrus polyphenols encapsulated in liposomes was evaluated against Staphylococcus aureus and Staphylococcus epidermidis, the most common agents in ocular infections. The formulation activity against planktonic staphylococci was tested by broth microdilution and sub-inhibitory concentrations were used to evaluate the effect on biofilm formation using the crystal violet (CV) assay. The eradicating effect of the preparation on mature biofilms was investigated by the CV assay, plate count, and confocal laser scanning microscopy. The product was bactericidal against staphylococci at a dilution of 1:2 or 1:4 and able to reduce biofilm formation even if diluted at 1:64. The formulation also had the ability to reduce the biomass of mature biofilms without affecting the number of cells, suggesting activity on the extracellular matrix. Overall, our results support the application of the used liposome-encapsulated polyphenols as an anti-biofilm strategy to counter biofilm-associated ocular infections.

Anti-staphylococcal activity of a polyphenol-rich citrus extract: synergy with β-lactams and low proficiency to induce resistance

“…These studies focused on its use as surface cleaner or supported its application as food treatment in the food industry. The citrus extract is also included as active ingredient in a liposomal formulation commercialized as medical device for the ocular antisepsis ( Vagge et al, 2021 ; Mencucci et al, 2022 ; Mazzantini et al, 2024 ). Nevertheless, evidence on the potential application of B in the clinical practice to treat staphylococcal infections is still lacking.…”

“…In this study, S. aureus ATCC 6538, S. aureus ATCC 43300, S. epidermidis ATCC 35984, and two S. epidermidis clinical isolates (named CI-1 and CI-2) were used ( Mazzantini et al, 2024 ). All strains were propagated on Mueller-Hinton Agar (MHA; Thermo Fisher Scientific, Waltham, United States) at 37°C for 24 h. For the antimicrobial susceptibility assays by broth microdilution, cation-adjusted Mueller-Hinton Broth (CAMHB; Merck KGaA, Darmstadt, Germany) containing 20–25 mg/L of calcium and 10–12.5 mg/L of magnesium was used ( European Committee on Antimicrobial Susceptibility Testing, 2022 ).…”