The differential adherence capabilities of two Listeria monocytogenes strains in monoculture and multispecies biofilms as a function of temperature

Aims: To determine the differential adherence capabilities at three different temperatures of Listeria monocytogenes Scott A, a clinical food pathogen, and L. monocytogenes FM876, a persistent strain from a milk-processing environment, to stainless steel. Methods and Results: Differential adherence was investigated by submerging stainless steel coupons in both 48-h Listeria monocultures and mixed cultures additionally containing Staphylococcus xylosus DP5H and Pseudomonas fragi ATCC 4973. Immunofluorescent microscopy and image analysis techniques were utilized to identify and quantify the L. monocytogenes cells adhering to the steel at 4 degreesC, 18 degreesC and 30 degreesC. The monoculture biofilms consistently contained greater L. monocytogenes numbers than the multispecies biofilms, with the persistent strain FM876 showing significantly greater adherence than strain Scott A. Optimum adherence occurred at 18 degreesC in monoculture biofilms. Conclusions: L. monocytogenes strains exhibit differential, temperature-dependent, adherence to stainless steel. Significance and Impact of the Study: These results demonstrate temperature dependent biofilm adherence and support previous findings that persistent strains exhibit increased adherence capability.