Purpose: The purpose of this study was to determine if Lmo0753 contributes to persistence- and virulence-related mechanisms of motility, biofilm formation, hemolytic activity, and intracellular survival and growth.
Methods: Motility assays of strains 10403S and EGD-e, along with their respective Δlmo0753mutants, were conducted for 48 h at 37, 25, and 4ºC on BHI soft-agar plates. Crystal violet biofilm assays were conducted at 37ºC and 25ºC on glass and plastic surfaces for 48 h in BHI and 1% peptone water. For listeriolysin O-associated hemolytic assays, serial dilutions of supernatants of each strain and mutant were made followed by addition of sheep red blood cells, incubation for 30 min at 37ºC and subsequent OD quantification. For intracellular assays, monolayers of mammalian cell cultures J774 and Caco-2 were grown to confluency, infected, and every 2 h bacterial growth was enumerated.
Results: Lmo0753 plays a significant role in flagellar motility (P < 0.05) in 10403S at 37°C and 25ºC and EGDe at 4ºC. Significant decreases (P < 0.0001) in biofilm production and hemolytic activity (P < 0.05) were also observed for Δlmo0753in 10403S and EGDe. Lmo0753 appeared to contribute to the intracellular growth of both 10403S and EGDe in J774 cells but not in Caco-2 cells.
Significance: Findings from this study may help to elucidate the specific role of Lmo0753 in L. monocytogenes toward a better understanding of the persistence and virulence mechanisms of this pathogen.