A molecular marker for evaluating the pathogenic potential of foodborne Listeria monocytogenes.
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.
Jacquet
Christine
C
Laboratoire des Listeria, Centre National de Référence des Listeria, World Health Organization Collaborating Center for Foodborne Listeriosis, Institut Pasteur, Paris, France.
Doumith
Michel
M
Gordon
Jeffrey I
JI
Martin
Paul M V
PM
Cossart
Pascale
P
Lecuit
Marc
M
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
D001426:Bacterial Proteins; D015415:Biomarkers; C116311:internalin H protein, Listeria monocytogenes