The Effects of a Concentrated Surfactant Gel on Biofilm EPS

The aim of this study was to evaluate if a poloxamer-based concentrated surfactant gel (CSG), containing antibacterial preservative agents, had the ability to reduce the levels of biofilm extracellular polymeric substances (EPS), specifically proteins and extracellular DNA (eDNA), as these are found to be the most immunogenic, within an in vitro biofilm.

A 24-hour biofilm of P. aeruginosa ATCC 15442 was grown in a 12-well plate and treated for 24 hours with a CSG coated onto Multisorb® (BSN Medical Limited, Hull, United Kingdom). EPS were extracted from each sample using 1M sodium chloride. Protein and DNA in EPS extractions was determined quantitatively using the Pierce™ Coomassie (Bradford) protein assay kit and a microplate SYTO 9™ (ThermoFisher Scientific, Paisley, United Kingdom) fluorescent assay, respectively. Protein and DNA was also determined qualitatively using confocal laser scanning microscopy (CLSM).

Following 24-hour growth of P. aeruginosa ATCC 15442 biofilm, 7.38mg/mL protein was isolated from the extracted EPS in the untreated control. In comparison, the protein concentration found in the extracted EPS from biofilms treated with a CSG was 6.39mg/mL, showing a 13.4% reduction. Following 24-hour growth of P. aeruginosa ATCC 15442 biofilm, 11.71mg/mL eDNA was isolated from the extracted EPS in the untreated control. In comparison, the eDNA concentration found in the extracted EPS from biofilms treated with a CSG was 0.65mg/mL, showing a 94.5% reduction. Following statistical analysis of the data, the decrease in protein isolated following CSG treatment was within error; however, the decrease in eDNA isolated was statistically significant, showing the ability of the CSG to break up biofilm EPS in vitro. Using confocal laser microscopy and staining techniques, a large quantity of protein and eDNA could be observed in samples from the untreated control. In comparison, a reduction in EPS protein and eDNA was observed in samples that had been treated with a CSG.

The data presented here potentially shows the ability of a CSG to reduce components of the P. aeruginosa biofilm EPS. The reduction in eDNA following CSG treatment may contribute to the dispersal of the biofilm, potentially increasing the susceptibility of it to antimicrobials, and should be explored further.