Complete genome of the barotolerant Listeria monocytogenes RO15 strain and comparison with other strains isolated from food and food processing environments
Abstract Background Consumption of Listeria monocytogenes contaminated food can cause infection with a high mortality rate in humans and animals. High pressure processing (HPP) is a non-thermal preservation technique adopted by the food industry to inactivate food pathogens, including L. monocytogenes. Strains of L. monocytogenes show different level of resistance to the high pressure. Some strains resist up to 500 MPa pressure. Here, we tested the pressure resistance of 10 different L. monocytogenes strains, including field isolates and widely used type strains, to 400 and 600 MPa pressure treatments. Genome sequencing, and genome comparison of the tested L. monocytogenes strains were performed to investigate the relation between genomic profile and pressure resistance. Results In this study, we showed that none of the tested strains were resistant to 600 MPa, more than 5 log 10 reduction observed for all strains after 1 minute 600 MPa pressure treatment. However, L. monocytogenes strain RO15 showed no significant reduction in viable cell counts after 400 MPa for 1 minute and it was defined as barotolerant. Genome sequencing of so far unsequenced L. monocytogenes strain RO15, 2HF33, MB5, AB199, AB120, C7, and RO4 allowed us to compare their gene content. Genome comparison of 10 tested strains showed that the three most pressure tolerant strains had more than one CRISPR system with self-targeting spacers. Further, several anti-CRISPR genes were detected in these strains. Pan-genome wide analysis showed that 10 prophage genes were significantly associated with the three most barotolerant strains. Conclusions L. monocytogenes strain RO15 was the most pressure tolerant among the selected strains. Genome comparison suggests that there might be a relationship with prophages, CRISPR systems and pressure resistance in L. monocytogenes .