Purpose: To determine the effect of pre-and post-exposure of delmopinol hydrochloride on the prevention and removal of Listeria monocytogenes 1/2a and S. enterica Agona biofilms on stainless steel.
Methods: Biofilm formation - Stainless steel blanks (2cm x 2cm) were spot-inoculated on the finished surface with 20µl of a 109 CFU/ml liquid culture, placed inoculated side down onto TSA, and incubated for 24h at 25°C. Following biofilm formation, blanks were rinsed with phosphate buffered saline (PBS), vortexed for 90s in PBS, and surface-plated onto TSA for enumeration. In pre-exposure studies, the blanks were submerged in delmopinol hydrochloride solution (0.2% and 0.5%) for 1, 5, and 10 min prior to biofilm formation. In post-exposure studies, the blanks received no pretreatment with delmopinol but were exposed to the solution as above after biofilm formation.
Results: Pre-exposure of the blanks to 0.2% delmopinol resulted in a significant decrease in L. monocytogenes concentration at 1, 5 and 10 min exposures (P < 0.05). However, pre-exposures with the 0.5% solution had no significant effect on L. monocytogenes biofilm populations (P > 0.05). All post-exposures lead to a significant decline in biofilm concentrations (P < 0.05). Post-exposures of 10 minutes exhibited a mean log reduction of 5.59 and 6.40 for 0.2% and 0.5% delmopinol solutions, respectively. For S. Agona, pre-exposure resulted in minimal reductions in bacterial recovery (P < 0.05). Whereas, post-exposures of 10 min exhibited a mean log reductions of 7.65 and 7.75 for 0.2% and 0.5% delmopinol solutions, respectively.
Significance: Delmopinol hydrochloride was significantly better for removing L. monocytogenes and S. Agona biofilms on stainless steel than preventing them.