Purpose: To investigate the anti-biofilm activity of trimethylsilane (TMS) and TMS+oxygen (1:8) plasma coating on silicone and high density polyethylene (HDPE) food contact surfaces.
Methods: Silicone and HDPE wafers were coated with TMS and TMS+O2 (1:8) plasma. Two groups of mixed-species biofilms, Listeria monocytogenes (LM) and Salmonella enterica (SE); and Escherichia coli O157:H7 (EC) and SE, were formed on the wafers for 48 h. The pour-plate method was conducted to determine bacterial counts.
Results: No significant reduction in counts of the mixed species biofilm of LM SCOTT A and SE I4-10 was observed on coated silicone. However, the same mixed groups were significantly reduced (>1 log CFU/wafer) on HDPE surfaces by the TMS+O2 (1:8) treatment. Further, when comparing counts of LM in a single species biofilm with those in the mixed biofilm, the results showed a greater reduction in the mix which implied that antagonistic interactions among the LM and SE species were also responsible for its reduction. Counts of the mixed species biofilm of EC 505b with SE I4-10 on TMS+O2 (1:8) coated silicone decreased by more than 1 log CFU/wafer. However, neither strain was affected by either plasma treatment on HDPE surfaces, indicating that the anti-biofilm efficacy of coated HDPE was less than that for silicone.
Significance: This study shows that TMS and TMS+O2 (1:8)-coated silicone and HDPE surfaces could significantly inhibit certain mixed-species biofilms. Further, the interactions between the bacteria in a mixed biofilm also played a role in the reduction of a single species in the biofilm.