Effectiveness of a phage cocktail as a biocontrol agent against L. monocytogenes biofilms

•Biofilm is a serious problem in food industry.•L. monocytogenes can develop biofilm.•ListShieldTM can reduce L. monocytogenes in biofilms.

Listeria monocytogenes can persist and form biofilms in a food environment which are difficult to eradicate because biofilms are inherently resistant to a variety of antimicrobial treatments. Therefore, alternative approaches such as bacteriophages have been suggested as a promising biocontrol agent against biofilms. The aim of this study was to evaluate the efficacy of a cocktail bacteriophage product (ListShield™) against L. monocytogenes biofilms. These biofilms were established on lettuce, stainless steel, rubber, and a MBEC biofilm device and exposed to the ListShield™ phage preparation (1 × 108 PFU/mL) for 2 h. ListShield™ had sufficient potency to significantly reduce the biofilm (P < 0.05) in all cases. Biofilm reduction achieved after ListShield™ treatment on the stainless steel coupon was 1.9-2.4 log CFU/cm2 and on the rubber surface approximately 1.0 log CFU/cm2. Phage application on lettuce inactivated biofilm bacteria up to 0.7 log CFU/cm2. These results suggest that bacteriophage preparation ListShield™ is an effective tool for the inactivation of L. monocytogenes biofilms in the food industry.