Phenotypic profiling supports that Listeria costaricensis lacks in vitro pathogenicity but exhibits persistence...

Listeria costaricensis was recently isolated from a food-processing facility. However, its pathogenic potential and persistence capacity remain poorly characterized at the phenotypic level, raising concerns about food safety. Therefore, we assessed its pathogenic potential through phenotypic invasion and adhesion assays in HeLa cells, showing that L. costaricensis cannot invade HeLa cells despite displaying a cell adhesion capacity comparable to that of Listeria monocytogenes and Listeria innocua reference strains. Given the industrial origin of the strain, we further evaluated its susceptibility to commonly used disinfectants by broth microdilution, finding susceptibility to a mixture of quaternary ammonium compounds (MIC < 100 µg/mL), and reduced susceptibility to peracetic acid (MIC > 160 µg/mL) and sodium hypochlorite (MIC > 500 µg/mL). Considering its demonstrated adhesion capacity, we assessed its ability to form biofilms on polystyrene surfaces, reporting a weak biofilm-forming phenotype comparable to other L. monocytogenes strains. Finally, using the VFanalyzer platform we identified on the L. costaricensis genome 28 virulence-associated gene sequences related to regulatory and structural functions, adherence, and an incomplete invasion gene group compared to L. monocytogenes strains. Collectively, these findings phenotypically support the previously proposed non-pathogenic nature of L. costaricensis, while also revealing a level of persistence comparable to other L. monocytogenes isolates.