Characterization and In Vitro Efficacy against Listeria monocytogenes of a Newly Isolated Bacteriophage, φIZSAM-1

Listeria monocytogenes is a bacterial pathogen responsible of listeriosis, a disease that in humans is often related to the contamination of ready-to-eat foods. Phages are candidate biodecontaminants of pathogenic bacteria thanks to their ability to lyse prokaryotes while being safe for eukaryotic cells. In this study, phi IZSAM-1 was isolated from the drain-waters of an Italian blue cheese plant and showed lytic activity against antimicrobial resistant Listeria monocytogenes strains. This phage was subjected to purification and in vitro efficacy tests. The results showed that at multiplicities of infection (MOIs) <= 1, phages were able to keep Listeria monocytogenes at low optical density values up to 8 h, with bacterial counts ranging from 1.02 to 3.96 log(10) units lower than the control. Besides, phi IZSAM-1 was further characterized, showing 25 principal proteins (sodium dodecyl sulfate polyacrylamide gel electrophoresis profile) and a genome of approximately 50 kilo base pairs. Moreover, this study describes a new approach to phage isolation for applications in Listeria monocytogenes biocontrol in food production. In particular, the authors believe that the selection of phages from the same environments where pathogens live could represent a new approach to successfully integrating the control measures in an innovative, cost effective, safe and environmentally friendly way.

Automated summary

Listeria monocytogenes is a pathogenic bacterium responsible for listeriosis, which can be transmitted through contaminated ready-to-eat foods. Phages like phi IZSAM-1 have shown potential as biodecontaminants for drug-resistant Listeria monocytogenes strains, demonstrating effective control in vitro experiments. This study highlights the importance of phage isolation from the same environments as the target pathogens for successful biocontrol applications in food production.