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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT AND USE OF PHYLOGENETIC SYSTEMS TO ENHANCE FOOD SAFETY AND FOOD SECURITY

Location: Bacterial Foodborne Pathogens & Mycology Research Unit

Title: Utilization of a multiplex single nucleotide polymorphism (SNP) genotyping assay to determine the prevalence of virulence-attenuating mutations in inlA among human clinical and food isolates

Authors
item Van Stelten, A - COLORADO STATE UNIV
item Ward, Todd
item Wiedmann, M - CORNELL UNIV, ITHACA NY
item Nightingale, K - COLORADO STATE UNIV

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 21, 2009
Publication Date: May 21, 2009
Citation: Van Stelten, A., Ward, T.J., Wiedmann, M., Nightingale, K.K. 2009. Utilization of a multiplex single nucleotide polymorphism (SNP) genotyping assay to determine the prevalence of virulence-attenuating mutations in inlA among human clinical and food isolates. Meeting Abstract.

Technical Abstract: Listeria monocytogenes is a human foodborne pathogen that may cause severe invasive disease in susceptible individuals. L. monocytogenes utilizes the virulence factor Internalin A (inlA) to cross host cell barriers during the establishment of a systemic infection. At least 18 naturally occurring point mutations leading to a premature stop codon (PMSC) in inlA have been described worldwide and our previous work demonstrated that these mutations appear to be fully responsible for attenuated mammalian virulence. While previous studies investigated the distribution of select inlA PMSC mutations among subtypes known to include isolates with these mutations, there is a clear need to determine the prevalence of virulence-attenuating mutations in inlA among a large representative collection of L. monocytogenes isolates from ready-to-eat (RTE) foods and human clinical cases, to ultimately predict the public health risk associated with specific L. monocytogenes subtypes for future risk assessments. We thus assembled a large well-characterized set of L. monocytogenes isolates from human clinical cases (n=508) and RTE foods (n=501) isolated in the United States over the same time frame. We developed a multiplex single nucleotide polymorphism (SNP) genotyping assay to detect virulence-attenuating mutations in inlA and employed this assay to screen for the presence or absence of PMSC mutations in inlA among the set of human clinical and food isolates described above. SNP genotyping results showed that 3.7% of human clinical isolates carry a PMSC mutation in inlA, while 43.3% of isolates from RTE foods contain a virulence-attenuating mutation in inlA. A chi-square test of independence showed that inlA PMSCs were significantly more common among RTE food isolates than human clinical isolates (P < 0.0001), supporting that a significant proportion of L. monocytogenes found in RTE foods have limited human virulence. Results provided here will facilitate development of an accurate dose response model for L. monocytogenes with and without PMSCs in inlA and provide critical data for future L. monocytogenes risk assessments and regulatory initiatives.

Last Modified: 7/28/2014
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