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Rhamnolipid Micelles Assist Azithromycin in Efficiently Disrupting Staphylococcus aureus Biofilms and Impeding Their
Shiyu Lin1, Xiaojuan Li1, Yuning Zhang1
1Innovative Engineering Research Center of Veterinary Pharmaceutics, Department of Pharmacy, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, Sichuan, 611130, People's Republic of China.
Introduction:
Biofilm is highly resistant to antibiotics due to its heterogeneity and is implicated in over 80% of chronic infections; these refractory and relapse-prone infections pose a huge medical burden.
Methods:
In this study, rhamnolipid (RHL), a biosurfactant with antibiofilm activity, was loaded with the antibiotic azithromycin (AZI) to construct a stable nanomicelle (AZI@RHL) that promotes Staphylococcus aureus (S. aureus) biofilm disruption.
Results:
AZI@RHL micelles made a destruction in biofilms. The biofilm biomasses were reduced significantly by 48.2% (P<0.05), and the main components polysaccharides and proteins were reduced by 47.5% and 36.8%, respectively. These decreases were about 3.1 (15.9%), 7.3 (6.5%), and 1.9 (19.5%) times higher compared with those reported for free AZI. The disruption of biofilm structure was observed under a confocal microscope with fluorescent labeling, and 48.2% of the cells in the biofilm were killed. By contrast, the clearance rates of cells were only 20% and 17% when treated alone with blank micelles or free AZI. Biofilm formation was inhibited up to 92% in the AZI@RHL group due to effects on cell auto-aggregation and eDNA release. The rates for the other groups were significantly lower, with only 27.7% for the RHL group and 12% for the AZI group (P<0.05). The low cell survival and great formation inhibition could reduce biofilm recolonization and re-formation.
Conclusion:
The antibiofilm efficacy of rhamnolipid was improved through micellar nanoparticle effects when loading azithromycin. AZI@RHL provides a one-step solution that covers biofilm disruption, bacteria inactivation, recolonization avoidance, and biofilm re-formation inhibition.
Insights
This study developed azithromycin-loaded rhamnolipid nanomicelles (AZI@RHL) to combat antibiotic-resistant biofilms. AZI@RHL effectively disrupted biofilms, killed bacteria, and prevented regrowth, offering a promising solution for chronic infections.
Area of Science:
- Biotechnology
- Materials Science
- Infectious Diseases
Background:
- Bacterial biofilms are highly resistant to antibiotics, contributing to over 80% of chronic infections.
- These persistent infections present a significant medical and economic burden due to their refractory and relapsing nature.
Purpose of the Study:
- To develop a novel nanomicelle system encapsulating azithromycin (AZI) with rhamnolipid (RHL) for enhanced antibiofilm activity.
- To investigate the efficacy of the AZI@RHL nanomicelles in disrupting Staphylococcus aureus biofilms and preventing their reformation.
Main Methods:
- Rhamnolipid (RHL), a biosurfactant, was utilized to load the antibiotic azithromycin (AZI) into stable nanomicelles (AZI@RHL).
- The antibiofilm efficacy of AZI@RHL was evaluated by measuring biofilm biomass reduction, component degradation (polysaccharides, proteins), and bacterial cell killing rates.
- Confocal microscopy was used to visualize biofilm structure disruption, and inhibition of biofilm formation was assessed by monitoring cell auto-aggregation and eDNA release.
Main Results:
- AZI@RHL significantly reduced biofilm biomass by 48.2%, with substantial decreases in polysaccharides (47.5%) and proteins (36.8%).
- The nanomicelles achieved 48.2% bacterial cell killing within the biofilm, significantly outperforming free AZI (17%) and blank micelles (20%).
- Biofilm formation was inhibited by up to 92% with AZI@RHL, demonstrating superior efficacy over RHL (27.7%) and free AZI (12%) in preventing regrowth.
Conclusions:
- Loading azithromycin into rhamnolipid nanomicelles significantly enhances its antibiofilm efficacy.
- AZI@RHL offers a comprehensive one-step solution for managing biofilms, including disruption, bacterial inactivation, and prevention of recolonization and reformation.
