Investigating the effect of rosmarinic acid loaded magnetic nanoparticles against growth and biofilm formation of Staphylococcus aureus isolated from poultry meat.

Abstract

Background: Staphylococcus aureus, one of the causes of food poisoning, plays an important role in causing gastrointestinal inflammation.

Aims: Given the spread of antibiotic resistance in S. aureus, the present study aimed to investigate the effect of rosmarinic acid (RA) loaded magnetic nanoparticles (Fe₃O₄NPs@RA) on inhibiting the growth and biofilm formation of S. aureus isolated from meat samples.

Methods: Fe₃O₄NPs@RA have been synthesized and their antimicrobial activities were investigated against S. aureus isolated from poultry meat by broth micro-dilution. The anti-biofilm effect of these nanoparticles and their effect on the expression level of biofilm-associated genes were investigated using microplate and real-time PCR methods. The killing properties of Fe₃O₄NPs@RA against test bacteria investigated by time-kill assay.

Results: The minimum inhibitory concentration (MIC) of Fe₃O₄NPs@RA against S. aureus isolates ranged from 31.2-125 µg/ml. Also, the treatment with a sub-MIC concentration of Fe₃O₄NPs@RA prevented the formation of biofilm by 50-82%, in different isolates and downregulated the expression level of icaA and icaD. Also, the treatment with the MIC concentration of Fe₃O₄NPs@RA caused a 2.4-fold decrease in the population of living bacteria after 4 h and the number of living bacteria decreased more than 99% after 8 h. In the cytotoxicity assay, during 48 h, Fe₃O₄NPs@RA had no cytotoxic effect on HEK-293 cells at concentrations lower than of 300 µg/ml.

Conclusion: The results of the present study showed that Fe₃O₄NPs@RA were effective in inhibiting the growth and biofilm formation of S. aureus isolates and could be further investigated as an option for controlling S. aureus in food samples.