title: Highly Invasive Listeria monocytogenes Strains Have Growth and Invasion Advantages in Strain Competition.
abstract: Multiple Listeria monocytogenes strains can be present in the same food sample; moreover, infection with more than one L. monocytogenes strain can also occur. In this study we investigated the impact of strain competition on the growth and in vitro virulence potential of L. monocytogenes. We identified two strong competitor strains, whose growth was not (or only slightly) influenced by the presence of other strains and two weak competitor strains, which were outcompeted by other strains. Cell contact was essential for growth inhibition. In vitro virulence assays using human intestinal epithelial Caco2 cells showed a correlation between the invasion efficiency and growth inhibition: the strong growth competitor strains showed high invasiveness. Moreover, invasion efficiency of the highly invasive strain was further increased in certain combinations by the presence of a low invasive strain. In all tested combinations, the less invasive strain was outcompeted by the higher invasive strain. Studying the effect of cell contact on in vitro virulence competition revealed a complex pattern in which the observed effects depended only partially on cell-contact suggesting that competition occurs at two different levels: i) during co-cultivation prior to infection, which might influence the expression of virulence factors, and ii) during infection, when bacterial cells compete for the host cell. In conclusion, we show that growth of L. monocytogenes can be inhibited by strains of the same species leading potentially to biased recovery during enrichment procedures. Furthermore, the presence of more than one L. monocytogenes strain in food can lead to increased infection rates due to synergistic effects on the virulence potential.
authors.affiliation: Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece.
authors.forename: Evangelia A
authors.initials: EA
authors.lastname: Zilelidou
authors.affiliation: Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Vienna, Austria.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Rychli
authors.affiliation: Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece.
authors.forename: Evanthia
authors.initials: E
authors.lastname: Manthou
authors.affiliation: Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Vienna, Austria; "Dunarea de Jos" University of Galaţi, Galaţi, Romania.
authors.forename: Luminita
authors.initials: L
authors.lastname: Ciolacu
authors.affiliation: Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Wagner
authors.affiliation: Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece.
authors.forename: Panagiotis N
authors.initials: PN
authors.lastname: Skandamis
mesh_terms: D018938:Caco-2 Cells; D006801:Humans; D008089:Listeria monocytogenes / Q000254:growth & development* / Q000472:pathogenicity*; D008088:Listeriosis / Q000378:metabolism; D013045:Species Specificity; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D037521:Virulence Factors