Effect of silver nanoparticles conjugated to thiosemicarbazide on biofilm formation and expression of intercellular adhesion molecule genes, icaAD, in Staphylococcus aureus.

Biofilm formation is regarded as an important factor in the establishment of infections caused by Staphylococcus aureus. In the present study, phenotypic and molecular assays were used to evaluate antibiofilm potential of thiosemicarbazide (Tsc) conjugated with silver nanoparticles (Ag NPs) and functionalized by glutamic acid (Ag@Glu/Tsc NPs) against methicillin-resistant S. aureus (MRSA). Ag NPs were synthesized using precipitation method and conjugated to Tsc using glutamic acid. The NPs were characterized using SEM and FTIR spectroscopy analyses. Then, antibiofilm potential of the prepared NPs against MRSA strains was evaluated using phenotypic method and their effects on the expression of biofilm-associated genes icaA and icaD. Finally, the genes involved with the synthesis of intercellular adhesion molecules were determined. According to the results, Ag@Glu/Tsc NPs inhibited biofilm formation of MRSA strains up to 76.7% compared with the control. In addition, expression of the biofilm-associated genes icaA and icaD reduced by 66.7% and 60.3%, respectively in the presence of sub-inhibitory concentration of Ag@Glu/Tsc NPs. In conclusion, Ag@Glu/Tsc NPs could be considered as a potent antibacterial agent to inhibit bacterial biofilms.