Virulence aspects of Listeria monocytogenes LO28 high pressure-resistant variants

High pressure treatment is a novel food processing approach for reducing pathogens in foods and food ingredients. However, relatively little is known about the pathogenic potential of organisms that survive the treatment. Twelve previously isolated and characterized variants of Listeria monocytogenes LO28 obtained after a high pressure treatment were assessed for their virulence potential and antibiotic susceptibility. Ten variants showed attenuated virulence while two variants retained full virulence in a mouse model of infection. Seven of the attenuated variants demonstrated a reduction in virulence factor activity. Compared to the wild type, all variants exhibited similar or increased susceptibility to multiple antibiotics commonly used in listeriosis treatment. •Most variants surviving high pressure treatment displayed reduced virulence.•Nearly all piezotolerant variants were slightly more susceptible to antibiotics.•Mutations in or upstream of ctsR resulted in different virulence phenotypes.•Two of the twelve variants retained full virulence in a mouse model of infection.•Full virulent multiple stress-resistant variants may pose an increased health risk.