title: Listeria monocytogenes Isolates Carrying Virulence-Attenuating Mutations in Internalin A Are Commonly Isolated from Ready-to-Eat Food Processing Plant and Retail Environments.
abstract: Listeria monocytogenes is a human foodborne pathogen that may cause an invasive disease known as listeriosis in susceptible individuals. Internalin A (InlA; encoded by inlA) is a virulence factor that facilitates crossing of host cell barriers by L. monocytogenes . At least 19 single nucleotide polymorphisms (SNPs) in inlA that result in a premature stop codon (PMSC) have been described worldwide. SNPs leading to a PMSC in inlA have been shown to be causally associated with attenuated virulence. L. monocytogenes pathogens carrying virulence-attenuating (VA) mutations in inlA have been commonly isolated from ready-to-eat (RTE) foods but rarely have been associated with human disease. This study was conducted to determine the prevalence of VA SNPs in inlA among L. monocytogenes from environments associated with RTE food production and handling. More than 700 L. monocytogenes isolates from RTE food processing plant (n = 409) and retail (n = 319) environments were screened for the presence of VA SNPs in inlA. Overall, 26.4% of isolates from RTE food processing plant and 32.6% of isolates from retail environments carried a VA mutation in inlA. Food contact surfaces sampled at retail establishments were significantly (P < 0.0001) more likely to be contaminated by a L. monocytogenes isolate carrying a VA mutation in inlA (56% of 55 isolates) compared with nonfood contact surfaces (28% of 264 isolates). Overall, a significant proportion of L. monocytogenes isolated from RTE food production and handling environments have reduced virulence. These data will be useful in the revision of current and the development of future risk assessments that incorporate strain-specific virulence parameters.
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523.|Department of Animal and Food Sciences, Texas Tech University, Lubbock, Texas 79409.
authors.forename: A
authors.initials: A
authors.lastname: VAN Stelten
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523.|Department of Biological and Physical Sciences, Montana State University, Billings, Montana 59101.
authors.forename: A R
authors.initials: AR
authors.lastname: Roberts
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523.|Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Manuel
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523.
authors.forename: K K
authors.initials: KK
authors.lastname: Nightingale
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D005511:Food Handling; D005516:Food Microbiology; D006801:Humans; D008089:Listeria monocytogenes / Q000235:genetics*; D008088:Listeriosis; D009154:Mutation; D014774:Virulence
chemical_list: D001426:Bacterial Proteins
keywords: Listeria monocytogenes; Mutations; Premature stop codon; Single nucleotide polymorphism; Virulence attenuating; inlA