title: Prevalence and distribution of Listeria monocytogenes inlA alleles prone to phase variation and inlA alleles with premature stop codon mutations among human, food, animal, and environmental isolates.
abstract: In Listeria monocytogenes, 18 mutations leading to premature stop codons (PMSCs) in the virulence gene inlA have been identified to date. While most of these mutations represent nucleotide substitutions, a frameshift deletion in a 5' seven-adenine homopolymeric tract (HT) in inlA has also been reported. This HT may play a role in phase variation and was first identified among L. monocytogenes lineage II ribotype DUP-1039C isolates. In order to better understand the distribution of different inlA mutations in this ribotype, a newly developed multiplex real-time PCR assay was used to screen 368 DUP-1039C isolates from human, animal, and food-associated sources for three known 5' inlA HT alleles: (i) wild-type (WT) (A7), (ii) frameshift (FS) (A6), and (iii) guanine interruption (A2GA4) alleles. Additionally, 228 DUP-1039C isolates were screened for all inlA PMSCs; data on the presence of all inlA PMSCs for the other 140 isolates were obtained from previous studies. The statistical analysis based on 191 epidemiologically unrelated strains showed that strains with inlA PMSC mutations (n = 41) were overrepresented among food-associated isolates, while strains encoding full-length InlA (n = 150) were overrepresented among isolates from farm animals and their environments. Furthermore, the A6 allele was overrepresented and the A7 allele was underrepresented among food isolates, while the A6 allele was underrepresented among farm and animal isolates. Our results indicate that genetic variation in inlA contributes to niche adaptation within the lineage II subtype DUP-1039C.
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Clyde S
authors.initials: CS
authors.lastname: Manuel
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins, Colorado, USA Department of Animal and Food Sciences, Texas Tech University, Lubbock, Texas, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Van Stelten
authors.affiliation: Department of Food Science, Cornell University, Ithaca, New York, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Wiedmann
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins, Colorado, USA Department of Animal and Food Sciences, Texas Tech University, Lubbock, Texas, USA.
authors.forename: Kendra K
authors.initials: KK
authors.lastname: Nightingale
authors.affiliation: Department of Food Science, Cornell University, Ithaca, New York, USA rho2@cornell.edu.
authors.forename: Renato H
authors.identifier: http://orcid.org/0000-0003-4933-9817
authors.initials: RH
authors.lastname: Orsi
mesh_terms: D000483:Alleles; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D018389:Codon, Nonsense / Q000235:genetics; D005516:Food Microbiology; D005787:Gene Frequency / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008089:Listeria monocytogenes / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D008088:Listeriosis / Q000382:microbiology; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D018389:Codon, Nonsense; C069761:internalin protein, Bacteria