Genotypes Associated withListeria monocytogenesIsolates Displaying Impaired or Enhanced Tolerances to Cold, Salt, Acid, or Desiccation Stress.
The human pathogenListeria monocytogenesis a large concern in the food industry where its continuous detection in food products has caused a string of recalls in North America and Europe. Most recognized for its ability to grow in foods during refrigerated storage,L. monocytogenescan also tolerate several other food-related stresses with some strains possessing higher levels of tolerances than others. The objective of this study was to use a combination of phenotypic analyses and whole genome sequencing to elucidate potential relationships betweenL. monocytogenesgenotypes and food-related stress tolerance phenotypes. To accomplish this, 166L. monocytogenesisolates were sequenced and evaluated for their ability to grow in cold (4°C), salt (6% NaCl, 25°C), and acid (pH 5, 25°C) stress conditions as well as survive desiccation (33% RH, 20°C). The results revealed that the stress tolerance ofL. monocytogenesis associated with serotype, clonal complex (CC), full lengthinlAprofiles, and the presence of a plasmid which was identified in 55% of isolates. Isolates with full lengthinlAexhibited significantly (p< 0.001) enhanced cold tolerance relative to those harboring a premature stop codon (PMSC) in this gene. Similarly, isolates possessing a plasmid demonstrated significantly (p= 0.013) enhanced acid tolerance. We also identified nine newL. monocytogenessequence types, a newinlAPMSC, and several connections between CCs and the presence/absence or variations of specific genetic elements. A whole genome single-nucleotide-variants phylogeny revealed sporadic distribution of tolerant isolates and closely related sensitive and tolerant isolates, highlighting that minor genetic differences can influence the stress tolerance ofL. monocytogenes. Specifically, a number of cold and desiccation sensitive isolates contained PMSCs in σBregulator genes (rsbS, rsbU, rsbV). Collectively, the results suggest that knowing the sequence type of an isolate in addition to screening for the presence of full-lengthinlAand a plasmid, could help food processors and food agency investigators determine why certain isolates might be persisting in a food processing environment. Additionally, increased sequencing ofL. monocytogenesisolates in combination with stress tolerance profiling, will enhance the ability to identify genetic elements associated with higher risk strains.
Department of Food, Nutrition, and Health, University of British Columbia Vancouver, BC, Canada.
Patricia
P
Hingston
Department of Food, Nutrition, and Health, University of British Columbia Vancouver, BC, Canada.
Jessica
J
Chen
Department of Molecular Biology and Biochemistry, Simon Fraser University Burnaby, BC, Canada.
Bhavjinder K
BK
Dhillon
Laboratory for Foodborne Zoonoses, Public Health Agency of Canada Lethbridge, AB, Canada.
Chad
C
Laing
Department of Molecular Biology and Biochemistry, Simon Fraser University Burnaby, BC, Canada.
Claire
C
Bertelli
Laboratory for Foodborne Zoonoses, Public Health Agency of Canada Lethbridge, AB, Canada.
Victor
V
Gannon
Institute for Food Safety and Hygiene, University of Zurich Zurich, Switzerland.
Taurai
T
Tasara
Department of Food, Nutrition, and Health, University of British Columbia Vancouver, BC, Canada.
Kevin
K
Allen
Department of Molecular Biology and Biochemistry, Simon Fraser University Burnaby, BC, Canada.
Fiona S L
FS
Brinkman
Division for Microbiology and Production, National Food Institute, Technical University of Denmark Kongens Lyngby, Denmark.
Lisbeth
L
Truelstrup Hansen
Department of Food, Nutrition, and Health, University of British Columbia Vancouver, BC, Canada.
Siyun
S
Wang
Listeria monocytogenes; food safety; internalin A; plasmids; sequence typing; stress tolerance; whole genome sequencing