Biofilm Removal and Antimicrobial Activities of Agar Hydrogel Containing Colloid Nano-Silver against Staphylococcus aureus and Salmonella typhimurium

Antibacterial and biofilm removal effects of agar hydrogel incorporating silver nanoparticles (SNP) at various concentrations were studied against Staphylococcus aureus and Salmonella typhimurium in vitro.
The minimum inhibitory concentrations (MIC) of SNP was determined by agar dilution method. Then, hydrogels were prepared by mixing of 0.5% w/v agar and SNP (1/2 MIC, MIC, and 2 MIC) and their inhibitory efficacies against planktonic and biofilm forms of bacteria were measured using agar spot and microtiter test, respectively.
The MIC value was 125 µg/ mL for both bacteria. All SNP hydrogels represented antibacterial activity against Staphylococcus aureus and S. typhimurium on agar culture, which was significant compared to control group (silver sulfadiazine cream). The developed biofilm of S. aureus and S. typhimurium were strongly (85% reduction) and modernly affected (60% reduction) by SNP hydrogels during 15 min contact time, respectively. A dose-dependent biofilm reduction was not demonstrated when different SNP concentrations were tested. Moreover, the results from this study confirmed the moderate sanitizing ability of SNP loaded hydrogel against planktonic forms of both bacteria, which SNP (2MIC) hydrogel decreased only 2.3 log10 CFU/ mL in a primary population of S. typhimurium during 15 min exposure time.
We recommended SNP incorporated agar hydrogel as an effective biofilm removal sanitizer.