Combined application of Zinc and Iron nanoparticles with bacteriophagetherapy against antibiotic-resistant Staphylococcus aureus biofilms

This study investigated the combined antibacterial and anti-biofilm effects of zinc oxide
nanoparticles, iron oxide nanoparticles, and a newly isolated bacteriophage, BacPhage-
SAU27, against Staphylococcus aureus SAU27as a multidrug-resistant strain. The study
aimed to evaluate the potential synergistic effects of phage–nanoparticle combinations
in combating biofilm-related infections caused by multidrug-resistant S. aureus. S.
aureus was cultured and evaluated for biofilm formation. BacPhage-SAU27 was isolated
from wastewater using the double-layer agar method and characterized by plaque assays.
The minimum inhibitory concentration of zinc oxide nanoparticles and iron oxide
nanoparticles was determined individually and in combination, and BacPhage-SAU27
was added to assess interaction effects. Biofilm formation and destruction were analyzed
using crystal violet staining and scanning electron microscopy, and the fractional
inhibitory concentration index was calculated. The minimum inhibitory concentrations
for zinc oxide nanoparticles and iron oxide nanoparticles were 120 μg/mL and 72 μg/mL,
respectively. The combination of both nanoparticles reduced the minimum inhibitory
concentration to 25 μg/mL. Adding BacPhage-SAU27 further reduced the minimum
inhibitory concentration to 15 μg/mL for zinc oxide nanoparticles and 18 μg/mL for iron
oxide nanoparticles and lowered the multiplicity of infection to 0.00001. BacPhage-
SAU27 alone and in combination with nanoparticles significantly inhibited biofilm
formation and caused biofilm destruction. Scanning electron microscopy confirmed
damaged biofilm structures and complete bacterial clearance with the phage–
nanoparticle combination. The combination of BacPhage-SAU27 with zinc oxide and
iron oxide nanoparticles offers a promising strategy to combat S. aureus biofilms and
may provide an alternative to antibiotic therapies.
Keywords: Staphylococcus aureus; Antibiotic-resistant bacteria; Phage; Iron and zinc
nanoparticles.