P3-137 Genetic Diversity of Listeria monocytogenes Strains Recovered from the Food Sector in British Columbia, Canada

Wednesday, July 25, 2012
Exhibit Hall (Rhode Island Convention Center)
Jovana Kovacevic, University of British Columbia, Vancouver, Canada
Lorraine McIntyre, BC Centre for Disease Control, Vancouver, Canada
Ana Paccagnella, BC Centre for Disease Control, Vancouver, Canada
Linda Hoang, BC Centre for Disease Control, Vancouver, Canada
Judy Isaac-Renton, BC Centre for Disease Control, Vancouver, Canada
Kevin Allen, University of British Columbia, Vancouver, Canada
Introduction: Listeria monocytogenes (Lm) is an environmentally ubiquitous pathogen and a frequent contaminant of ready-to-eat foods. Studies examining the prevalence of Listeria spp. in British Columbia (BC), Canada, found problems with Lm contamination in fish, and to a lesser degree in dairy and meat sectors. However, little is known about strain relatedness, and potential virulence risk of Lm in the BC food continuum.

Purpose: To assess diversity and virulence potential of Lm isolates recovered from BC’s food chain.

Methods: Culture methods were used to recover Lm from food and environmental samples. Isolates were serotyped and subjected to pulsed-field gel electrophoresis (PFGE). Based on PFGE, premature stop codons (PMSC) within inlA were screened by DNA sequencing in 56 unique isolates.

Results: In total, 111 Lm isolates were recovered from three dairy, seven fish and five meat facilities. Isolates serotyped as 1/2a (42%), 4b (37%), 1/2c (12%), 1/2b (5%), and 3a (4%). PMSCs in inlA were observed in 36% of isolates, including eight 1/2b, six 1/2a, four 3a, and one 1/2b and 4b Lm serotype. Conversely, no PMSCs were seen in 64% of isolates (20 4b, 15 1/2a and one 1/2b), though 23% possessed a previously unreported three-codon deletion in positions 738-740. PFGE revealed 36 unique pulsotypes; closely related patterns were observed in dairy and meat, fish and meat, but not dairy and fish facilities. More than one Lm serotype and pulsotype were seen in 54% and 69% of the facilities, respectively. 

Significance: Genetically diverse Lm strains were observed across different food facilities. Most strains belonged to listeriosis-causing serotypes encoding a full-length InlA protein required for disease. Accordingly, Lm recovered along the BC food continuum, and specifically fish, may pose high risk to the consuming public.