Phenotypic and Genotypic Characterization of AtypicalListeria monocytogenesandListeria innocuaIsolated from Swine Slaughterhouses and Meat Markets

In the last decade, atypicalListeria monocytogenesandL. innocuastrains have been detected in food and the environment. Because of mutations in the major virulence genes, these strains have different virulence intensities in eukaryotic cells. In this study, we performed phenotypic and genotypic characterization of atypicalL. monocytogenesandL. innocuaisolates obtained from swine slaughterhouses and meat markets. Forty strains were studied, including isolates ofL. monocytogenesandL. innocuawith low-hemolytic activity. The isolates were characterized using conventional phenotypicListeriaidentification tests and by the detection and analysis ofL. monocytogenes-specific genes. Analysis of 16S rRNA was used for the molecular identification of theListeriaspecies. TheL. monocytogenesisolates were positive for all of the virulence genes studied. The atypicalL. innocuastrains were positive forhly, plcA,andinlC. Mutations in the InlC, InlB, InlA, PI-PLC, PC-PLC, and PrfA proteins were detected in the atypical isolates. Furtherin vitroand transcriptomic studies are being developed to confirm the role of these mutations inListeriavirulence.