The researchers found that plastic composition and the presence of other microorganisms had the greatest influence on L. monocytogenes persistence. Among the materials tested, PP consistently supported greater L. monocytogenes accumulation in multispecies biofilms, while line-patterned surfaces generally promoted higher pathogen persistence than smooth surfaces under mixed-species conditions.

The study also showed that interactions with background microorganisms could either enhance or suppress L. monocytogenes survival, depending on the surface material. Pseudomonas fluorescens consistently promoted L. monocytogenes biofilm formation across nearly all plastic types and topographies, whereas Escherichia coli O157:H7 and Ralstonia insidiosa produced either synergistic or antagonistic effects depending on the specific surface.

Notably, the researchers found that conventional indicators such as surface roughness and wettability alone did not reliably predict L. monocytogenes biofilm formation. In some cases, smoother plastics supported greater biofilm accumulation than rougher surfaces, suggesting that material chemistry and microbial interactions play a larger role than previously recognized.

The authors said their findings demonstrate that pathogen persistence on plastic food contact surfaces is governed by the combined effects of material composition, engineered surface topography, and microbial ecology rather than any single factor. They suggested that P. fluorescens, PP surfaces, and line-patterned topographies could serve as practical indicators of elevated L. monocytogenes persistence risk in food processing environments.

The researchers noted that the study was conducted under controlled laboratory conditions using simulated produce processing environments. They said further research is needed to better understand how these surface-dependent microbial interactions occur in commercial food processing facilities and to inform future sanitation strategies and food contact surface design.