P-020. Identification of Epidemiologically Relevant SNPs of Listeria Monocytogenes Epidemic Clones using PFGE Banding Patterns and Ligation-Mediated PCR

Y. Chen, S. Knabel;
Penn State Univ., University Park, PA.

Listeria monocytogenes epidemic clone II has caused two significant listeriosis outbreaks: an outbreak linked to contaminated hot dogs (U.S., 1998-1999) and an outbreak linked to contaminated turkey deli meats (U.S., 2002). The isolates of these two outbreaks are closely related. Previously, AscI-PFGE was the only subtyping method that could distinguish the 1998 outbreak isolates as a group from the 2002 outbreak isolates. The only differences between the two AscI-PFGE patterns are the ~650 Kbp fragment in the 1998 outbreak clone and the ~320 Kbp and ~330 Kbp fragments in the 2002 outbreak clone. One hypothesis regarding the cause of this banding pattern difference is that a point mutation generated an AscI restriction site which split the ~650 Kbp fragment into the ~320 Kbp and ~330 Kbp fragments. In the present study, a fragment-end ligation-mediated PCR strategy was used to analyze the AscI macrorestriction fragments of L. monocytogenes epidemic clone II and identified the single nucleotide polymorphism (SNP) in the prophage region that caused the PFGE banding pattern differences. Multiple epidemiologically relevant SNPs were subsequently identified that allow rapid differentiation of the 1998 outbreak isolates and the 2002 outbreak isolates.

179/P. Foodborne Pathogens - II

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