title: Examination of food chain-derived Listeria monocytogenes strains of different serotypes reveals considerable diversity in inlA genotypes, mutability, and adaptation to cold temperatures.
abstract: Listeria monocytogenes strains belonging to serotypes 1/2a and 4b are frequently linked to listeriosis. While inlA mutations leading to premature stop codons (PMSCs) and attenuated virulence are common in 1/2a, they are rare in serotype 4b. We observed PMSCs in 35% of L. monocytogenes isolates (n = 54) recovered from the British Columbia food supply, including serotypes 1/2a (30%), 1/2c (100%), and 3a (100%), and a 3-codon deletion (amino acid positions 738 to 740) seen in 57% of 4b isolates from fish-processing facilities. Caco-2 invasion assays showed that two isolates with the deletion were significantly more invasive than EGD-SmR (P < 0.0001) and were either as (FF19-1) or more (FE13-1) invasive than a clinical control strain (08-5578) (P = 0.006). To examine whether serotype 1/2a was more likely to acquire mutations than other serotypes, strains were plated on agar with rifampin, revealing 4b isolates to be significantly more mutable than 1/2a, 1/2c, and 3a serotypes (P = 0.0002). We also examined the ability of 33 strains to adapt to cold temperature following a downshift from 37°C to 4°C. Overall, three distinct cold-adapting groups (CAG) were observed: 46% were fast (<70 h), 39% were intermediate (70 to 200 h), and 15% were slow (>200 h) adaptors. Intermediate CAG strains (70%) more frequently possessed inlA PMSCs than did fast (20%) and slow (10%) CAGs; in contrast, 87% of fast adaptors lacked inlA PMSCs. In conclusion, we report food chain-derived 1/2a and 4b serotypes with a 3-codon deletion possessing invasive behavior and the novel association of inlA genotypes encoding a full-length InlA with fast cold-adaptation phenotypes.
authors: Food, Nutrition and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada.
authors: Jovana
authors: J
authors: Kovacevic
authors: Carolina
authors: C
authors: Arguedas-Villa
authors: Anna
authors: A
authors: Wozniak
authors: Taurai
authors: T
authors: Tasara
authors: Kevin J
authors: KJ
authors: Allen
mesh_terms: D000220:Adaptation, Biological; D001426:Bacterial Proteins / Q000235:genetics*; D001955:British Columbia; D018938:Caco-2 Cells; D003080:Cold Temperature; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004847:Epithelial Cells / Q000382:microbiology; D005516:Food Microbiology; D014644:Genetic Variation; D006801:Humans; D008089:Listeria monocytogenes / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C069761:internalin protein, Bacteria