Epidemic Clone I-Specific Genetic Markers in Strains of <i>Listeria monocytogenes</i> Serotype 4b from Foods

DOI Web Site 2 Citations
  • Suleyman Yildirim
    Department of Food Science, North Carolina State University, Raleigh, North Carolina
  • Wen Lin
    Food and Drug Administration, Irvine, California
  • Anthony D. Hitchins
    Food and Drug Administration, Washington, D.C.
  • Lee-Ann Jaykus
    Department of Food Science, North Carolina State University, Raleigh, North Carolina
  • Eric Altermann
    Department of Food Science, North Carolina State University, Raleigh, North Carolina
  • Todd R. Klaenhammer
    Department of Food Science, North Carolina State University, Raleigh, North Carolina
  • Sophia Kathariou
    Department of Food Science, North Carolina State University, Raleigh, North Carolina

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p> <jats:italic>Listeria monocytogenes</jats:italic> contamination of ready-to-eat foods has been implicated in numerous outbreaks of food-borne listeriosis. However, the health hazards posed by <jats:italic>L. monocytogenes</jats:italic> detected in foods may vary, and speculations exist that strains actually implicated in illness may constitute only a fraction of those that contaminate foods. In this study, examination of 34 serogroup 4 (putative or confirmed serotype 4b) isolates of <jats:italic>L. monocytogenes</jats:italic> obtained from various foods and food-processing environments, without known implication in illness, revealed that many of these strains had methylation of cytosines at GATC sites in the genome, rendering their DNA resistant to digestion by the restriction endonuclease Sau3AI. These strains also harbored a gene cassette with putative restriction-modification system genes as well as other, genomically unlinked genetic markers characteristic of the major epidemic-associated lineage of <jats:italic>L. monocytogenes</jats:italic> (epidemic clone I), implicated in numerous outbreaks in Europe and North America. This may reflect a relatively high fitness of strains with these genetic markers in foods and food-related environments relative to other serotype 4b strains and may partially account for the repeated involvement of such strains in human food-borne listeriosis. </jats:p>

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