title: A molecular marker for evaluating the pathogenic potential of foodborne Listeria monocytogenes.
abstract: BACKGROUND
  Internalin mediates entry of Listeria monocytogenes into some human cultured cell lines and crossing of the intestinal barrier in transgenic mice expressing its receptor, human E-cadherin, in enterocytes. The relevance of these findings for humans is challenged by the observation that some L. monocytogenes isolates express a truncated nonfunctional form of internalin.
  
  
  METHODS
  We investigated expression of internalin by use of immunoblot assay in 300 clinical strains obtained in France in a single year and a representative set of 150 strains obtained from food products during the same period.
  
  
  RESULTS
  Clinical strains expressed full-length internalin far more frequently (288/300 strains [96%]) than did strains recovered from food products (98/150 strains [65%]; odds ratio, 12.73; 95% confidence interval, 6.27-26.34; P<1 x 10(-7)). All 61 strains (100%) from pregnancy-related cases, 55 (98%) of 56 strains from patients with central nervous system infections, and 151 (93%) of 162 strains from patients with bacteremia expressed full-length internalin. All 110 strains belonging to serovar 4b, the most frequently implicated serovar in human listeriosis, expressed full-length internalin.
  
  
  CONCLUSIONS
  This study demonstrates the critical role of internalin in the pathogenesis of human listeriosis. It provides a molecular explanation for the predominance of serovar 4b among clinical strains and supports the usefulness of studying the expression of internalin as a marker of virulence in humans.
authors.affiliation: Laboratoire des Listeria, Centre National de Référence des Listeria, World Health Organization Collaborating Center for Foodborne Listeriosis, Institut Pasteur, Paris, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Jacquet
authors.forename: Michel
authors.initials: M
authors.lastname: Doumith
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Gordon
authors.forename: Paul M V
authors.initials: PM
authors.lastname: Martin
authors.forename: Pascale
authors.initials: P
authors.lastname: Cossart
authors.forename: Marc
authors.initials: M
authors.lastname: Lecuit
mesh_terms: D016470:Bacteremia / Q000382:microbiology; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000378:metabolism; D015415:Biomarkers; D002494:Central Nervous System Infections / Q000382:microbiology; D005260:Female; D005516:Food Microbiology; D006801:Humans; D015151:Immunoblotting; D008089:Listeria monocytogenes / Q000378:metabolism* / Q000472:pathogenicity*; D008088:Listeriosis / Q000382:microbiology*; D011247:Pregnancy; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D015415:Biomarkers; C116311:internalin H protein, Listeria monocytogenes