Biofilm dynamics of Listeria monocytogenes and Ralstonia insidiosa under cheese processing and aging conditions

We investigated Listeria monocytogenes(Lm)-Ralstonia insidiosa(Ri) biofilm dynamics and sanitizer-tolerance under cheesemaking(22°C) and cheese-aging(11°C) conditions. Strains of Lm(n=3) and Ri(n=2) were paired and simultaneously cultured on stainless steel coupons at 11°C and 22°C. The Biofilms were imaged on Days 1, 3, and 10 using SEM and enumerated after sanitizer treatment. Ri thrived at 11°C (p=0.0003) but was more susceptible to sanitizers at 22°C (p=0.034757) and more resilient with increasing maturity(p=0.000536). Biofilms morphed from sparse cell aggregates with web-like extracellular polymeric substances (EPS) into 3D structures with gel-like EPS by day-10. Findings highlight the need for time-sensitive sanitation regimens for cheese-aging surfaces.