Comparison of threeListeria monocytogenesstrains in a guinea-pig model simulating food-borne exposure

Abstract

Three different Listeria monocytogenes strains, LO28 (a laboratory strain with truncated InlA), 4446 (a clinical isolate) and 7291 (a food isolate), were compared in a guinea-pig model designed to mimic food-borne exposure. The objectives were (1) to verify the applicability of the animal model for distinguishing between Listeria with different virulence properties and (2) to explore whether it was possible to reduce the required number of animals by dosing with mixed cultures instead of monocultures. Consistent with in vitro observations of infectivity in Caco-2 cells, faecal densities and presence in selected organs were considerably lower for LO28 than for the other two strains. Additionally, the animal study revealed a difference in prevalence in faeces as well as in internal organs between the clinical isolate and the food isolate, which was not reproduced in vitro. Dosage with monocultures of Listeria strains gave similar results as dosage with a mixture of the three strains; thus, the mixed infection approach was a feasible way to reduce the number of animals needed for determination of listerial virulence.

Survival ofListeria monocytogenesin Simulated Gastrointestinal System and Transcriptional Profiling of Stress- and Adhesion-Related Genes

“…Lineage classification on the basis of partial actA sequence indicated that the five strains fell into lineages I and II (Table 1), which is consistent with the aforementioned serogroup result and previous reports (Ragon et al, 2008;Roldgaard et al, 2009).…”

Revelation by Single-Nucleotide Polymorphism Genotyping That Mutations Leading to a Premature Stop Codon in inlA Are Common among Listeria monocytogenes Isolates from Ready-To-Eat Foods but Not Human Listeriosis Cases

“…Eighteen naturally occurring mutations leading to a PMSC in inlA have been identified worldwide to date (5, 10, 11, 12, 22-25, 27, 29, 34, 35), and PMSC mutations in inlA have been shown to be causally associated with attenuated mammalian virulence (20,28). Mutations leading to a PMSC in inlA therefore represent a molecular marker for L. monocytogenes virulence attenuation, which can be used to predict the human health risk associated with consumption of foods contaminated by L. monocytogenes.…”

Genotypes Associated with Listeria monocytogenes Isolates Displaying Impaired or Enhanced Tolerances to Cold, Salt, Acid, or Desiccation Stress

“…Currently, one common molecular biomarker used for L. monocytogenes' virulence is the internalin A encoding gene ( inlA ) which can contain one of several different premature stop codons producing truncated and secreted proteins associated with attenuated virulence (Jonquieres et al, 1998; Jacquet et al, 2004; Rousseaux et al, 2004; Nightingale et al, 2005; Felicio et al, 2007; Handa-Miya et al, 2007; Roldgaard et al, 2009; Van Stelten et al, 2011). Recently, Kovacevic et al (2013) discovered that full-length variants of inlA were more prevalent among fast cold-adapting L. monocytogenes strains than intermediate and slow cold-adapting strains, suggesting that inlA profiling may also be suitable for predicting the cold tolerance of strains.…”