Zinc Oxide Nanoparticles Show Promise Against MRSA Biofilms

Zinc oxide nanoparticles (ZnONPs) could offer a low-cost strategy for combating methicillin-resistant Staphylococcus aureus (MRSA), according to new research. The study found that the nanoparticles not only inhibited bacterial growth but also substantially reduced biofilm formation, a key factor contributing to persistent and difficult-to-treat infections.

MRSA remains a leading cause of healthcare-associated infections worldwide and is associated with significant morbidity and mortality. Its ability to form biofilms—complex communities of bacteria protected by a self-produced extracellular matrix—makes infections particularly resistant to antibiotics and immune responses. As antimicrobial resistance continues to rise, researchers are increasingly investigating novel approaches to improve treatment outcomes.

MRSA Isolates Showed Extensive Antibiotic Resistance

Researchers analysed 131 clinical Staphylococcus aureus isolates collected from hospitals in Iran, confirming 58 (44.3%) as MRSA through molecular testing for the mecA and nuc genes.

Antimicrobial susceptibility testing revealed widespread resistance among MRSA isolates. All isolates were resistant to penicillin, while resistance to erythromycin reached 91.4% and ciprofloxacin resistance was observed in 74.1% of isolates. In contrast, all isolates remained susceptible to trimethoprim-sulfamethoxazole.

The findings reflect the continuing challenge of treating MRSA infections using conventional antibiotics and reinforce the need for alternative antimicrobial approaches.

Nanoparticles Inhibited Bacterial Growth

The investigators synthesised zinc oxide nanoparticles using a chemical precipitation method before assessing their antibacterial activity against the clinical isolates.

The nanoparticles inhibited MRSA growth across a broad concentration range, with a median minimum inhibitory concentration (MIC₅₀) of 64 µg/mL and an MIC₉₀ of 512 µg/mL. Notably, more than one-quarter of MRSA isolates were inhibited at concentrations of 16 µg/mL or lower, suggesting that some strains were highly susceptible to the nanoparticles.

Characterisation studies also confirmed that the synthesised nanoparticles were stable, with an average particle size of approximately 29 nm.

Significant Reduction in Biofilm Formation

The study also evaluated the ability of ZnONPs to disrupt MRSA biofilms.

Although only 15.5% of MRSA isolates were classified as strong biofilm producers, exposure to sub-inhibitory concentrations of zinc oxide nanoparticles reduced biofilm formation by an average of 82.3%. Because biofilms play a major role in chronic wound infections, implanted medical device infections, and persistent healthcare-associated infections, strategies that weaken biofilm formation could improve the effectiveness of existing antimicrobial therapies.

The researchers suggest that zinc oxide nanoparticles may interfere with bacterial adhesion and early biofilm development, although the precise mechanisms require further investigation.

Potential Alternative for Resource-Limited Settings

The authors conclude that zinc oxide nanoparticles represent a promising antimicrobial candidate against biofilm-associated MRSA infections. Given their relatively low production cost and demonstrated in vitro activity, the technology could prove particularly valuable in resource-limited healthcare settings where antimicrobial resistance poses a growing burden.

However, the researchers emphasise that these findings are based on laboratory experiments. Further in vivo studies and clinical trials will be necessary to determine the safety, efficacy, and practical applications of zinc oxide nanoparticles before they can be incorporated into routine MRSA treatment strategies.

Reference

Moghaddam AM et al. Synthesis of zinc oxide nanoparticles and their effect on biofilm of methicillin-resistant Staphylococcus aureus isolates. BMC Microbiol. 2026: DOI: 10.1186/s12866-026-05382-0.