Bacteriophage P100 application to control Listeria monocytogenes on smeared cheese

The antimicrobial activity of bacteriophage P100 against Listeria monocytogenes was studied under laboratory conditions, closely mimicking actual cheese making procedures. The laboratory cheese manufacture followed a normal protocol Munster cheese, including multiple smear treatments with selected yeast and Brevibacterium linens, as well as standard conditions for storage and maintenance. Various treatment strategies with the P100 phage were compared in their ability to suppress artificial L. monocytogenes contaminations. Depending on timing, frequency and dosage of the treatment, a significant reduction (of at least 3.5 logs) of Listeria viable counts was achieved compared to the non-treated controls. Phage P100 did not appear to interfere with the functional lactic acid bacteria in the cheese or to change the characteristics of the product. In conclusion, these results demonstrate a natural and effective treatment against L. monocytogenes contamination on surface-ripened cheeses. The model used in this study is representative for a broad range of applications in the cheese and food manufacture.