title: Intraspecific phylogeny and lineage group identification based on the prfA virulence gene cluster of Listeria monocytogenes.
abstract: Listeria monocytogenes is a serious food-borne pathogen that can cause invasive disease in humans and other animals and has been the leading cause of food recalls due to microbiological concerns in recent years. In order to test hypotheses regarding L. monocytogenes lineage composition, evolution, ecology, and taxonomy, a robust intraspecific phylogeny was developed based on prfA virulence gene cluster sequences from 113 L. monocytogenes isolates. The results of the multigene phylogenetic analyses confirm that L. monocytogenes comprises at least three evolutionary lineages, demonstrate that lineages most frequently (lineage 1) and least frequently (lineage 3) associated with human listeriosis are sister-groups, and reveal for the first time that the human epidemic associated serotype 4b is prevalent among strains from lineage 1 and lineage 3. In addition, a PCR-based test for lineage identification was developed and used in a survey of food products demonstrating that the low frequency of association between lineage 3 isolates and human listeriosis cases likely reflects rarity of exposure and not reduced virulence for humans as has been previously suggested. However, prevalence data do suggest lineage 3 isolates may be better adapted to the animal production environment than the food-processing environment. Finally, analyses of haplotype diversity indicate that lineage 1 has experienced a purge of genetic variation that was not observed in the other lineages, suggesting that the three L. monocytogenes lineages may represent distinct species within the framework of the cohesion species concept.
authors.affiliation: Microbial Genomics and Bioprocessing Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University St., Peoria, IL 61604, USA. wardtj@ncaur.usda.gov
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Ward
authors.forename: Lisa
authors.initials: L
authors.lastname: Gorski
authors.forename: Monica K
authors.initials: MK
authors.lastname: Borucki
authors.forename: Robert E
authors.initials: RE
authors.lastname: Mandrell
authors.forename: Jan
authors.initials: J
authors.lastname: Hutchins
authors.forename: Kitty
authors.initials: K
authors.lastname: Pupedis
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D019143:Evolution, Molecular; D005516:Food Microbiology; D006801:Humans; D008089:Listeria monocytogenes / Q000145:classification* / Q000235:genetics / Q000472:pathogenicity*; D008088:Listeriosis / Q000382:microbiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D010454:Peptide Termination Factors; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA; D012703:Serotyping; D015534:Trans-Activators / Q000235:genetics*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D010454:Peptide Termination Factors; D015534:Trans-Activators