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Lisbeth Truelstrup Hansen
National Food Institute, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark

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Journal article
Published: 30 January 2021 in Science of The Total Environment
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Residuals of antimicrobial products from anthropogenic uses can create a selective environment in domestic wastewater treatment systems and receiving environments and contribute to the spread of antimicrobial resistance (AMR). On-site wastewater treatment systems are widely used for domestic wastewater management in rural and remote regions, but the fate of determinants of AMR in these types of environments has received little attention. In this study, the mechanisms responsible for the attenuation of determinants of AMR in lateral flow sand filters were explored using a combination of lab, field and modeling investigations. The degradation kinetics and adsorption potential in the sand filter medium of three antibiotic resistance genes (ARGs; sul1, tetO, and ermB) and culturable bacteria resistant to sulfamethoxazole, tetracycline, and erythromycin were measured using lab experiments. The spatial distribution of ARGs and antibiotic resistant bacteria were also assessed in field scale sand filters, and mechanistic modeling was conducted to characterize filtration processes. The results indicated that the primary mechanisms responsible for AMR attenuation within the sand filters were degradation and filtration. The spatial distribution of AMR determinants illustrated that attenuation was occurring along the entire length of each filter. This study provides new insights on primary mechanisms of AMR attenuation in on-site wastewater treatment systems and supports the use of conservative design guidelines and separation distances for reducing AMR transmission.

ACS Style

Jennifer L. Hayward; Yannan Huang; Lisbeth Truelstrup Hansen; Christopher K. Yost; Craig Lake; Rob C. Jamieson. Fate and distribution of determinants of antimicrobial resistance in lateral flow sand filters used for treatment of domestic wastewater. Science of The Total Environment 2021, 767, 145481 .

AMA Style

Jennifer L. Hayward, Yannan Huang, Lisbeth Truelstrup Hansen, Christopher K. Yost, Craig Lake, Rob C. Jamieson. Fate and distribution of determinants of antimicrobial resistance in lateral flow sand filters used for treatment of domestic wastewater. Science of The Total Environment. 2021; 767 ():145481.

Chicago/Turabian Style

Jennifer L. Hayward; Yannan Huang; Lisbeth Truelstrup Hansen; Christopher K. Yost; Craig Lake; Rob C. Jamieson. 2021. "Fate and distribution of determinants of antimicrobial resistance in lateral flow sand filters used for treatment of domestic wastewater." Science of The Total Environment 767, no. : 145481.

Preprint content
Published: 27 November 2020
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Several Greenland seaweed species have potential as foods or food ingredients, both for local consumption and export. However, knowledge regarding their content of beneficial and deleterious elements on a species specific and geographical basis is lacking. This study investigated the content of 17 elements (As, Ca, Cd, Cr, Cu, Fe, Hg, I, K, Mg, Mn, Na, Ni, P, Pb, Se and Zn) in 77 samples of ten species (Agarum clathratum, Alaria esculenta, Ascophyllum nodosum, Fucus distichus, Fucus vesiculosus, Hedophyllum nigripes, Laminaria solidungula, Palmaria palmata, Saccharina latissima and Saccharina longicruris). Element profiles differed between species but showed similar patterns within the same family. For five species, different thallus parts were investigated separately, and showed different element profiles. A geographic origin comparison of Fucus species indicated regional differences. The seaweeds investigated were especially good sources of macrominerals (K > Na > Ca > Mg) and trace minerals, such as Fe. Iodine contents were high, especially in macroalgae of the family Laminariaceae. None of the samples exceeded the EU maximum levels for Cd, Hg or Pb, but some exceeded the stricter French regulations, especially for Cd and I. In conclusion, these ten species are promising food items.

ACS Style

Katharina Johanna Kreissig; Lisbeth Truelstrup Hansen; Pernille Erland Jensen; Susse Wegeberg; Ole Geertz-Hansen; Jens J Sloth. Characterisation and chemometric evaluation of 17 elements in ten seaweed species from Greenland. 2020, 1 .

AMA Style

Katharina Johanna Kreissig, Lisbeth Truelstrup Hansen, Pernille Erland Jensen, Susse Wegeberg, Ole Geertz-Hansen, Jens J Sloth. Characterisation and chemometric evaluation of 17 elements in ten seaweed species from Greenland. . 2020; ():1.

Chicago/Turabian Style

Katharina Johanna Kreissig; Lisbeth Truelstrup Hansen; Pernille Erland Jensen; Susse Wegeberg; Ole Geertz-Hansen; Jens J Sloth. 2020. "Characterisation and chemometric evaluation of 17 elements in ten seaweed species from Greenland." , no. : 1.

Journal article
Published: 11 November 2020 in Microorganisms
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The application of high-throughput DNA sequencing technologies (WGS) data remain an increasingly discussed but vastly unexplored resource in the public health domain of quantitative microbial risk assessment (QMRA). This is due to challenges including high dimensionality of WGS data and heterogeneity of microbial growth phenotype data. This study provides an innovative approach for modeling the impact of population heterogeneity in microbial phenotypic stress response and integrates this into predictive models inputting a high-dimensional WGS data for increased precision exposure assessment using an example of Listeria monocytogenes. Finite mixture models were used to distinguish the number of sub-populations for each of the stress phenotypes, acid, cold, salt and desiccation. Machine learning predictive models were selected from six algorithms by inputting WGS data to predict the sub-population membership of new strains with unknown stress response data. An example QMRA was conducted for cultured milk products using the strains of unknown stress phenotype to illustrate the significance of the findings of this study. Increased resistance to stress conditions leads to increased growth, the likelihood of higher exposure and probability of illness. Neglecting within-species genetic and phenotypic heterogeneity in microbial stress response may over or underestimate microbial exposure and eventual risk during QMRA.

ACS Style

Patrick Murigu Kamau Njage; Pimlapas Leekitcharoenphon; Lisbeth Truelstrup Hansen; Rene S. Hendriksen; Christel Faes; Marc Aerts; Tine Hald. Quantitative Microbial Risk Assessment Based on Whole Genome Sequencing Data: Case of Listeria monocytogenes. Microorganisms 2020, 8, 1772 .

AMA Style

Patrick Murigu Kamau Njage, Pimlapas Leekitcharoenphon, Lisbeth Truelstrup Hansen, Rene S. Hendriksen, Christel Faes, Marc Aerts, Tine Hald. Quantitative Microbial Risk Assessment Based on Whole Genome Sequencing Data: Case of Listeria monocytogenes. Microorganisms. 2020; 8 (11):1772.

Chicago/Turabian Style

Patrick Murigu Kamau Njage; Pimlapas Leekitcharoenphon; Lisbeth Truelstrup Hansen; Rene S. Hendriksen; Christel Faes; Marc Aerts; Tine Hald. 2020. "Quantitative Microbial Risk Assessment Based on Whole Genome Sequencing Data: Case of Listeria monocytogenes." Microorganisms 8, no. 11: 1772.

Journal article
Published: 18 September 2020 in International Journal of Hygiene and Environmental Health
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Reliable safe water supply is a pillar of society and a key to public health. The Nordic countries have an abundance of clean fresh water as a source for drinking water supplies. They have followed developments in safeguarding water, both the recommendations of the World Health Organization framework for safe drinking water and European legislation. Worldwide, including the Nordic countries, small water supplies are less compliant with water safety regulation. The forthcoming EU directive on drinking water require risk-based approaches and improved transparency on water quality. This research looks at the Nordic frameworks for safe water supply, with emphasis on risk-based approaches and smaller systems. We analyzed the legal frameworks for safe water, the structure of the water sector across the Nordic countries and explored how prepared these countries are to meet these requirements. Our findings show that, while legal requirements are mostly in place, delivery of information to the public needs to be improved. Most Nordic countries are in the process of implementing risk-based management in large and medium size water supplies, whereas small supplies are lagging. We conclude that a key to success is increased training and support for small supplies. We suggest wider adoption of the Nordic model of cooperation with benchmarking of safe water for all to transfer knowledge between the countries. This work provides insights into challenges and opportunities for the Nordic countries and provides insights relevant to countries worldwide in their effort towards realization of SDG Target 6.1.

ACS Style

Maria J. Gunnarsdottir; Sigurdur M. Gardarsson; Anna Charlotte Schultz; Hans-Jørgen Albrechtsen; Lisbeth Truelstrup Hansen; Kim Steve Gerlach Bergkvist; Pekka M. Rossi; Björn Klöve; Mette Myrmel; Kenneth M. Persson; Magnus Eriksson; Jamie Bartram. Status of risk-based approach and national framework for safe drinking water in small water supplies of the Nordic water sector. International Journal of Hygiene and Environmental Health 2020, 230, 113627 -113627.

AMA Style

Maria J. Gunnarsdottir, Sigurdur M. Gardarsson, Anna Charlotte Schultz, Hans-Jørgen Albrechtsen, Lisbeth Truelstrup Hansen, Kim Steve Gerlach Bergkvist, Pekka M. Rossi, Björn Klöve, Mette Myrmel, Kenneth M. Persson, Magnus Eriksson, Jamie Bartram. Status of risk-based approach and national framework for safe drinking water in small water supplies of the Nordic water sector. International Journal of Hygiene and Environmental Health. 2020; 230 ():113627-113627.

Chicago/Turabian Style

Maria J. Gunnarsdottir; Sigurdur M. Gardarsson; Anna Charlotte Schultz; Hans-Jørgen Albrechtsen; Lisbeth Truelstrup Hansen; Kim Steve Gerlach Bergkvist; Pekka M. Rossi; Björn Klöve; Mette Myrmel; Kenneth M. Persson; Magnus Eriksson; Jamie Bartram. 2020. "Status of risk-based approach and national framework for safe drinking water in small water supplies of the Nordic water sector." International Journal of Hygiene and Environmental Health 230, no. : 113627-113627.

Journal article
Published: 16 May 2020 in International Journal of Food Microbiology
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Listeria monocytogenes is a foodborne pathogen whose biofilm formation and desiccation tolerance may contribute to its survival in the food industry. L. monocytogenes possesses three cold-shock domain family proteins (CspA, CspB and CspD) known to be essential for adaptation against various food-relevant stress conditions including cold growth. The role of Csps in desiccation tolerance and biofilm formation was investigated in csp mutants as well as twenty-one other wild-type (WT) strains. Mutants with a single (ΔcspA) or multiple (ΔcspAB, ΔcspAD and ΔcspABD) deletions of csp genes, in a desiccation sensitive WT background (L. monocytogenes EGD-e) were immotile and exhibited an elevated desiccation tolerance compared to the parent strain. However, deletion of cspA in the more desiccation resistant food and outbreak related L. monocytogenes strains 568 and 08-5578 had no impact on desiccation tolerance although compared to the parent strains the mutants were also immotile. A correlation between lower motility and higher desiccation tolerance was observed among the 20 WT strains (Spearman rank correlation, rs = −0.56, p = 0.01), although exceptions occurred indicating that multiple factors influence the diverse desiccation tolerance among L. monocytogenes strains. Expression of cspA was upregulated in WT EGD-e, 568 and 08-5578 strains after desiccation for seven days, while the 568 and 08-5578 ΔcspA mutants expressed elevated levels of cspD and cspB (>30 fold higher) compared to their WTs. This indicates that upregulation of the other csps compensates for the deleted cspA gene. Although biofilm formation was improved in all EGDe csp mutants relative to the WT strain, the opposite was observed for 568 and 08-5578 WT strains and their cspA deletion mutants. Only motile strains formed biofilm in the peg lid assay but a significant negative correlation (rs = −0.60, p = 0.01) was seen between higher motility and higher biofilm formation of WT strains. In conclusion, the survival of L. monocytogenes strains in the food processing environment may depend on the control of motility, which is a necessity for biofilm formation but disadvantageous for desiccation survival.

ACS Style

Martin Laage Kragh; Francis Muchaamba; Taurai Tasara; Lisbeth Truelstrup Hansen. Cold-shock proteins affect desiccation tolerance, biofilm formation and motility in Listeria monocytogenes. International Journal of Food Microbiology 2020, 329, 108662 .

AMA Style

Martin Laage Kragh, Francis Muchaamba, Taurai Tasara, Lisbeth Truelstrup Hansen. Cold-shock proteins affect desiccation tolerance, biofilm formation and motility in Listeria monocytogenes. International Journal of Food Microbiology. 2020; 329 ():108662.

Chicago/Turabian Style

Martin Laage Kragh; Francis Muchaamba; Taurai Tasara; Lisbeth Truelstrup Hansen. 2020. "Cold-shock proteins affect desiccation tolerance, biofilm formation and motility in Listeria monocytogenes." International Journal of Food Microbiology 329, no. : 108662.

Original article
Published: 25 February 2020 in Journal of the American Oil Chemists' Society
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A ferrous oxidation‐xylenol orange (FOX) method was modified to measure the levels of hydroperoxides in highly pigmented sea cucumber (Cucumaria frondosa) viscera lipid. With the FOX method, oil hydroperoxides oxidize Fe(II) to Fe(III) ions, which in turn bind to xylenol orange (XO) to form a complex that has a maximum absorbance at 560 nm. When applied to lipid extracts containing high levels of carotenoid pigments, the carotenoids interfere in the absorbance measurement because the XO‐complex and carotenoids absorb at the same wavelength. To avoid this, an approach was developed where carotenoids were removed from the solution containing the XO‐complex before absorbance measurements were made. This was accomplished by aqueous extraction of the reaction solution, leaving an organic layer containing the carotenoid pigment. The absorbance of the aqueous layer was subsequently measured at 560 nm allowing for determination of the lipid hydroperoxide content (mmol kg−1) using a cumene hydroperoxide calibration curve. The method was validated using oxidized, unpigmented fish oils. The modified FOX method described herein was linear, accurate, and precise, and was validated over a hydroperoxide concentration range of 5–35 meq kg−1 lipid. This modified FOX method for hydroperoxide determination of highly pigmented lipids is a valuable alternative to the methods presently available for determination of peroxide values.

ACS Style

Reem Abuzaytoun; Suzanne Budge; Lisbeth Truelstrup Hansen; Shawna MacKinnon. Modification of the Ferrous Oxidation‐Xylenol Orange Method for Determination of Peroxide Value in Highly Pigmented Sea Cucumber Viscera Lipid. Journal of the American Oil Chemists' Society 2020, 97, 509 -516.

AMA Style

Reem Abuzaytoun, Suzanne Budge, Lisbeth Truelstrup Hansen, Shawna MacKinnon. Modification of the Ferrous Oxidation‐Xylenol Orange Method for Determination of Peroxide Value in Highly Pigmented Sea Cucumber Viscera Lipid. Journal of the American Oil Chemists' Society. 2020; 97 (5):509-516.

Chicago/Turabian Style

Reem Abuzaytoun; Suzanne Budge; Lisbeth Truelstrup Hansen; Shawna MacKinnon. 2020. "Modification of the Ferrous Oxidation‐Xylenol Orange Method for Determination of Peroxide Value in Highly Pigmented Sea Cucumber Viscera Lipid." Journal of the American Oil Chemists' Society 97, no. 5: 509-516.

Original research article
Published: 22 January 2020 in Frontiers in Microbiology
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The foodborne pathogen Listeria monocytogenes survives exposure to a variety of stresses including desiccation in the food industry. Strand-specific RNA sequencing was applied to analyze changes in the transcriptomes of two strains of L. monocytogenes (Lm 568 and Lm 08-5578) during desiccation [15°C, 43% relative humidity (RH)] on food grade stainless steel surfaces over 48 h to simulate a weekend with no food production. Both strains showed similar survival during desiccation with a 1.8–2 Log CFU/cm2 reduction after 48 h. Analysis of differentially expressed (DE) genes (>twofold, adjusted p-value <0.05) revealed that the initial response to desiccation was established after 6 h and remained constant with few new genes being DE after 12, 24, and 48 h. A core of 81 up- and 73 down-regulated DE genes were identified as a shared, strain independent response to desiccation. Among common upregulated genes were energy and oxidative stress related genes e.g., qoxABCD (cytochrome aa3) pdhABC (pyruvate dehydrogenase complex) and mntABCH (manganese transporter). Common downregulated genes related to anaerobic growth, proteolysis and the two component systems lmo1172/lmo1173 and cheA/cheY, which are involved in cold growth and flagellin production, respectively. Both strains upregulated additional genes involved in combatting oxidative stress and reactive oxygen species (ROS), including sod (superoxide dismutase), kat (catalase), tpx (thiol peroxidase) and several thioredoxins including trxAB, lmo2390 and lmo2830. Osmotic stress related genes were also upregulated in both strains, including gbuABC (glycine betaine transporter) and several chaperones clpC, cspA, and groE. Significant strain differences were also detected with the food outbreak strain Lm 08-5578 differentially expressing 1.9 × more genes (726) compared to Lm 568 (410). Unique to Lm 08-5578 was a significant upregulation of the expression of the alternative transcription factor σB and its regulon. A number of long antisense transcripts (lasRNA) were upregulated during desiccation including anti0605, anti0936, anti1846, and anti0777, with the latter controlling flagellum biosynthesis and possibly the downregulation of motility genes observed in both strains. This exploration of the transcriptomes of desiccated L. monocytogenes provides further understanding of how this bacterium encounters and survives the stress faced when exposed to dry conditions in the food industry.

ACS Style

Martin Laage Kragh; Lisbeth Truelstrup Hansen. Initial Transcriptomic Response and Adaption of Listeria monocytogenes to Desiccation on Food Grade Stainless Steel. Frontiers in Microbiology 2020, 10, 3132 .

AMA Style

Martin Laage Kragh, Lisbeth Truelstrup Hansen. Initial Transcriptomic Response and Adaption of Listeria monocytogenes to Desiccation on Food Grade Stainless Steel. Frontiers in Microbiology. 2020; 10 ():3132.

Chicago/Turabian Style

Martin Laage Kragh; Lisbeth Truelstrup Hansen. 2020. "Initial Transcriptomic Response and Adaption of Listeria monocytogenes to Desiccation on Food Grade Stainless Steel." Frontiers in Microbiology 10, no. : 3132.

Journal article
Published: 01 October 2019 in International Journal of Food Microbiology
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In this study, we show that growth and prolonged storage of Listeria monocytogenes at 4 °C can promote the selection of variants with enhanced cold and heat tolerance. Enhanced cold-tolerance (ECT) variants (n = 12) were successfully isolated from a strain with impaired cold growth abilities following 84 days of storage at 4 °C in brain heart infusion broth (BHIB). Whole genome sequencing, membrane fatty acid analysis, and stress tolerance profiling were performed on the parent strain and two ECT variants: one displaying regular-sized colonies and the other displaying small colonies when grown at 37 °C on BHI agar. Under cold stress conditions, the parent strain exhibited an impaired ability to produce branched-chain fatty acids which are known to be important for cold adaptation in L.monocytogenes. The ECT variants were able to overcome this limitation, a finding which is hypothesized to be associated with the identification of two independent single-nucleotide polymorphisms in genes encoding subunits of acetyl-coA carboxylase, an enzyme critical for fatty acid biosynthesis. While the ECT phenotype was not found to be associated with improved salt (BHIB + 6% NaCl, 25 °C), acid (BHIB pH 5, 25 °C) or desiccation (33% RH, 20 °C) tolerance, the small-colony variant exhibited significantly (p < 0.05) enhanced heat tolerance at 52 °C in buffered peptone water compared to the parent strain and the other variant. The results from this study demonstrate that the continuous use of refrigeration along the food-supply chain has the potential to select for L.monocytogenes variants with enhanced cold and heat tolerance, highlighting the impact that microbial intervention strategies can have on the evolution of bacterial strains and likewise, food safety.

ACS Style

Patricia A. Hingston; Lisbeth Truelstrup Hansen; Jean-François Pombert; Siyun Wang. Characterization of Listeria monocytogenes enhanced cold-tolerance variants isolated during prolonged cold storage. International Journal of Food Microbiology 2019, 306, 108262 .

AMA Style

Patricia A. Hingston, Lisbeth Truelstrup Hansen, Jean-François Pombert, Siyun Wang. Characterization of Listeria monocytogenes enhanced cold-tolerance variants isolated during prolonged cold storage. International Journal of Food Microbiology. 2019; 306 ():108262.

Chicago/Turabian Style

Patricia A. Hingston; Lisbeth Truelstrup Hansen; Jean-François Pombert; Siyun Wang. 2019. "Characterization of Listeria monocytogenes enhanced cold-tolerance variants isolated during prolonged cold storage." International Journal of Food Microbiology 306, no. : 108262.

Evaluation study
Published: 23 August 2019 in Food Microbiology
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The objective of this study was to develop a qPCR method for specific enumeration of viable Listeria monocytogenes in food processing facilities and heat treated products. Primers specific for L. monocytogenes were designed to amplify a short (199 bp) or long (1561 bp) fragment of the listeriolysin (hly) gene. The short- and long-amplicon qPCR methods with and without propidium monoazide (PMA) treatment of the cells were tested for their ability to discriminate between viable (no heat) and heat-killed cells (90 °C, 10 min). The PMA-qPCR methods were subsequently used to assess the survival of L. monocytogenes during desiccation (33% RH, 15 °C) on stainless steel surfaces for ten days with and without prior biofilm formation. The long-amplicon qPCR method had a limit of quantification (LOQ) of 1.32 log CFU/reaction (efficiency 92%, R2 = 0.991), while the LOQ for the short-amplicon qPCR method was 1.44 log CFU/reaction (efficiency 102%, R2 = 0.991). PMA was essential for detection of viable cells, and the long-amplicon PMA-qPCR significantly (p < 0.05) reduced the signal from heat-killed cells compared to the short-amplicon method. L. monocytogenes survival during desiccation without biofilm formation was accurately enumerated with the long-amplicon PMA-qPCR method. However, when L. monocytogenes had formed biofilm prior to desiccation, the long-amplicon PMA-qPCR accurately measured the log fold inactivation but underestimated the number of viable cells even with use of an optimized DNA extraction method. This long-amplicon PMA-qPCR method can aid in the detection and enumeration of viable L. monocytogenes cells to further the understanding of its survival and persistence in food processing facilities. The developed method was demonstrated to work on both heat and desiccation treated cells and highlights the importance of amplicon size in viability-qPCR.

ACS Style

Martin Laage Kragh; Mikala Thykier; Lisbeth Truelstrup Hansen. A long-amplicon quantitative PCR assay with propidium monoazide to enumerate viable Listeria monocytogenes after heat and desiccation treatments. Food Microbiology 2019, 86, 103310 .

AMA Style

Martin Laage Kragh, Mikala Thykier, Lisbeth Truelstrup Hansen. A long-amplicon quantitative PCR assay with propidium monoazide to enumerate viable Listeria monocytogenes after heat and desiccation treatments. Food Microbiology. 2019; 86 ():103310.

Chicago/Turabian Style

Martin Laage Kragh; Mikala Thykier; Lisbeth Truelstrup Hansen. 2019. "A long-amplicon quantitative PCR assay with propidium monoazide to enumerate viable Listeria monocytogenes after heat and desiccation treatments." Food Microbiology 86, no. : 103310.

Journal article
Published: 20 July 2019 in Toxins
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Listeria monocytogenes strains are known to harbour plasmids that confer resistance to sanitizers, heavy metals, and antibiotics; however, very little research has been conducted into how plasmids may influence L. monocytogenes’ ability to tolerate food-related stresses. To investigate this, a library (n = 93) of L. monocytogenes plasmid sequences were compared. Plasmid sequences were divided into two groups (G1 and G2) based on a repA phylogeny. Twenty-six unique plasmid types were observed, with 13 belonging to each of the two repA-based groups. G1 plasmids were significantly (p < 0.05) smaller than G2 plasmids but contained a larger diversity of genes. The most prevalent G1 plasmid (57,083 bp) was observed in 26 strains from both Switzerland and Canada and a variety of serotypes. Quantitative PCR (qPCR) revealed a >2-fold induction of plasmid-contained genes encoding an NADH peroxidase, cadmium ATPase, multicopper oxidase, and a ClpL chaperone protein during growth under salt (6% NaCl) and acid conditions (pH 5) and ProW, an osmolyte transporter, under salt stress conditions. No differences in salt and acid tolerance were observed between plasmid-cured and wildtype strains. This work highlights the abundance of specific plasmid types among food-related L. monocytogenes strains, the unique characteristics of G1 and G2 plasmids, and the possible contributions of plasmids to L. monocytogenes tolerance to food-related stresses.

ACS Style

Patricia Hingston; Thomas Brenner; Lisbeth Truelstrup Hansen; Siyun Wang. Comparative Analysis of Listeria monocytogenes Plasmids and Expression Levels of Plasmid-Encoded Genes during Growth under Salt and Acid Stress Conditions. Toxins 2019, 11, 426 .

AMA Style

Patricia Hingston, Thomas Brenner, Lisbeth Truelstrup Hansen, Siyun Wang. Comparative Analysis of Listeria monocytogenes Plasmids and Expression Levels of Plasmid-Encoded Genes during Growth under Salt and Acid Stress Conditions. Toxins. 2019; 11 (7):426.

Chicago/Turabian Style

Patricia Hingston; Thomas Brenner; Lisbeth Truelstrup Hansen; Siyun Wang. 2019. "Comparative Analysis of Listeria monocytogenes Plasmids and Expression Levels of Plasmid-Encoded Genes during Growth under Salt and Acid Stress Conditions." Toxins 11, no. 7: 426.

Journal article
Published: 03 July 2019 in Water Research
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The ability of lateral flow sand filters, used as on-site wastewater treatment systems (OWTS), to remove antibiotic resistance genes (ARGs), antibiotic resistant bacteria (ARB), and other relevant genetic markers (HF183, 16S rRNA, and int1) was assessed. Municipal wastewater was settled in a septic tank prior to loading into six pilot-scale lateral flow sand filters comprised of three different sand media types, at 5 and 30% slopes. The sand filters were sampled bi-weekly for: 9 ARGs and 3 other complimentary gene markers (sul1, sul2, qnrS, tetO, ermB, blaTEM, blaCTX-M, mecA, vanA, int1, HF183, 16S rRNA), and conventional microbial and water quality indicators, from July to November in 2017, and four times in the summer of 2018. The sand filters were observed to attenuate 7 of the ARGs to mostly below 2 log gene copies per mL. Log reductions ranging from 2.9 to 5.4 log were observed for the removal of absolute abundances of ARGs from septic tank effluent in 5 of the 6 sand filters. The fine-grained filter on the 5% slope did not perform as well for ARG attenuation due to hydraulic failure. The apportionment of cell-associated versus cell-free DNA was determined for the gene markers and this indicated that the genes were primarily carried intracellularly. Average log reductions of ARB with resistance to either sulfamethoxazole, erythromycin, or tetracycline were approximately 2.3 log CFU per mL within the filters compared to the septic tank effluent. This field study provides in-depth insights into the attenuation of ARB, ARGs, and their genetic compartmentalization in variably saturated sand OWTS. Overall, this type of OWTS was found to pose little risk of antimicrobial resistance contamination spread into surrounding environments when proper hydraulic function was maintained.

ACS Style

Jennifer L. Hayward; Yannan Huang; Christopher K. Yost; Lisbeth Truelstrup Hansen; Craig Lake; Anthony Tong; Rob C. Jamieson. Lateral flow sand filters are effective for removal of antibiotic resistance genes from domestic wastewater. Water Research 2019, 162, 482 -491.

AMA Style

Jennifer L. Hayward, Yannan Huang, Christopher K. Yost, Lisbeth Truelstrup Hansen, Craig Lake, Anthony Tong, Rob C. Jamieson. Lateral flow sand filters are effective for removal of antibiotic resistance genes from domestic wastewater. Water Research. 2019; 162 ():482-491.

Chicago/Turabian Style

Jennifer L. Hayward; Yannan Huang; Christopher K. Yost; Lisbeth Truelstrup Hansen; Craig Lake; Anthony Tong; Rob C. Jamieson. 2019. "Lateral flow sand filters are effective for removal of antibiotic resistance genes from domestic wastewater." Water Research 162, no. : 482-491.

Journal article
Published: 01 December 2018 in Science of The Total Environment
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Raw wastewater can contain high levels of antibiotic resistance genes (ARGs), making municipal wastewater treatment plants (WWTPs) critical for the control of the release of ARGs into the environment. The objective of this study was to investigate how individual treatment steps in two tertiary WWTPs affected the removal (copies/mL) and relative abundance of ARGs (copies/copies 16S rRNA genes). Nine ARG markers, representing resistance to commonly used antibiotics, as well as one integron gene (intl1) to assess ARG mobility potential, were quantified using quantitative real-time PCR (qPCR). Both WWTPs met provincial effluent regulations for removal of carbonaceous oxygen demand (CBOD5) and total suspended solids. Eight of the ten ARG markers (intl1, sul1, sul2, tet(O), ermB, blaCTX-M, blaTEM, qnrS) were detected in all samples. In contrast, mecA was detected intermittently and vanA remained below the detection limit in all samples. The total ARG marker abundances decreased by log 1.77 (p < 0.05) in the plant using an aerated lagoon (AL), and by 2.69 logs (p < 0.05) through treatment in the plant employing a biological nutrient removal (BNR) system. The BNR and secondary clarifier steps in both plants afforded the most removal of ARGs. The relative abundance of ARGs remained unchanged at the AL plant and showed a decreasing trend at the BNR plant. Levels of CBOD5, nitrate and the human Bacteroides fecal marker correlated with ARG concentrations, suggesting these variables may be useful in predicting ARG removal. In conclusion, the effluent coming from the WWTPs contained eight of the studied ARG markers in concentrations ranging from 0.01 to 3.6 log copies/mL, indicating their release into the environment, however, the relative abundance of ARGs was not enriched during treatment in the two WWTPs.

ACS Style

Mandy M. McConnell; Lisbeth Truelstrup Hansen; Rob C. Jamieson; Kara D. Neudorf; Christopher K. Yost; Anthony Tong. Removal of antibiotic resistance genes in two tertiary level municipal wastewater treatment plants. Science of The Total Environment 2018, 643, 292 -300.

AMA Style

Mandy M. McConnell, Lisbeth Truelstrup Hansen, Rob C. Jamieson, Kara D. Neudorf, Christopher K. Yost, Anthony Tong. Removal of antibiotic resistance genes in two tertiary level municipal wastewater treatment plants. Science of The Total Environment. 2018; 643 ():292-300.

Chicago/Turabian Style

Mandy M. McConnell; Lisbeth Truelstrup Hansen; Rob C. Jamieson; Kara D. Neudorf; Christopher K. Yost; Anthony Tong. 2018. "Removal of antibiotic resistance genes in two tertiary level municipal wastewater treatment plants." Science of The Total Environment 643, no. : 292-300.

Journal article
Published: 30 November 2018 in Science of The Total Environment
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Most arctic communities use primary wastewater treatment systems that are capable of only low levels of pathogen removal. Effluent potentially containing fecally derived microorganisms is released into wetlands and marine waters that may simultaneously serve as recreation or food harvesting locations for local populations. The purpose of this study is to provide the first estimates of acute gastrointestinal illness (AGI) attributable to wastewater treatment systems in Arctic Canada. A screening-level, point estimate quantitative microbial risk assessment model was developed to evaluate worst-case scenarios across an array of exposure pathways in five case study locations. A high annual AGI incidence rate of 5.0 cases per person is estimated in Pangnirtung, where a mechanical treatment plant discharges directly to marine waters, with all cases occurring during low tide conditions. The probability of AGI per person per single exposure during this period ranges between 1.0 × 10−1 (shore recreation) and 6.0 × 10−1 (shellfish consumption). A moderate incidence rate of 1.2 episodes of AGI per person is estimated in Naujaat, where a treatment system consisting of a pond and tundra wetland is used, with the majority of cases occurring during spring. The pathway with the highest individual probability of AGI per single exposure event is wetland travel at 6.0 × 10−1. All other risk probabilities per single exposure are <1.0 × 10−1. The AGI incidence rates estimated for the other three case study locations are <0.1. These findings suggest that wastewater treatment sites may be contributing to elevated rates of AGI in some arctic Canadian communities. Absolute risk values, however, should be weighed with caution based on the exploratory nature of this study design. These results can be used to inform future risk assessment and epidemiological research as well as support public health and sanitation decisions in the region.

ACS Style

Kiley Daley; Rob Jamieson; Daniel Rainham; Lisbeth Truelstrup Hansen; Sherilee L. Harper. Screening-level microbial risk assessment of acute gastrointestinal illness attributable to wastewater treatment systems in Nunavut, Canada. Science of The Total Environment 2018, 657, 1253 -1264.

AMA Style

Kiley Daley, Rob Jamieson, Daniel Rainham, Lisbeth Truelstrup Hansen, Sherilee L. Harper. Screening-level microbial risk assessment of acute gastrointestinal illness attributable to wastewater treatment systems in Nunavut, Canada. Science of The Total Environment. 2018; 657 ():1253-1264.

Chicago/Turabian Style

Kiley Daley; Rob Jamieson; Daniel Rainham; Lisbeth Truelstrup Hansen; Sherilee L. Harper. 2018. "Screening-level microbial risk assessment of acute gastrointestinal illness attributable to wastewater treatment systems in Nunavut, Canada." Science of The Total Environment 657, no. : 1253-1264.

Journal article
Published: 01 November 2018 in Science of The Total Environment
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In the Canadian Arctic, it is common practice to discharge municipal wastewater into tundra wetlands. Antibiotic resistant bacteria and the antibiotic resistance genes (ARGs) they contain can be present in municipal wastewater and there is a scarcity of knowledge on ARGs in wastewater in Arctic environments. This study was initiated on the fate of ARGs in tundra wetland ecosystems impacted by anthropogenic wastewater sources in Arctic communities. In the summer season of 2016, two wetlands were studied in the Inuit communities of Sanikiluaq and Naujaat in Nunavut, Canada. Genomic DNA was extracted from both soil and water during the spring freshet and late summer in the wetlands, and a suite of nine clinically relevant ARGs (sul1, sul2, mecA, vanA, qnrS, ermB, tetO, blaTEM, blaCTX-M), and an integron gene (int1) were analyzed using quantitative polymerase chain reaction (qPCR). Hydrological and water quality measurements were conducted in conjunction with the microbiological sampling. Gene targets were consistently present in the wastewater, and throughout both wetlands, except for vanA and mecA. Concentrations of ARGs were greater during the spring freshet, due to short hydraulic retention times (<2 days), which coincided with decreased treatment performance. The environmental resistome in un-impacted wetlands had above detection limit concentrations of int1, sul1, sul2, blaCTX-M in water in Naujaat, and sul1, qnrS and tetO in soil in Sanikiluaq. First-order rate constants were widely variable and specific to the gene target. ARGs were present in concentrations elevated above baseline reference sites in tundra wetlands influenced by municipal wastewater, and hydrological conditions had a large impact on their spatial distribution and levels.

ACS Style

Jennifer L. Hayward; Amy J. Jackson; Christopher K. Yost; Lisbeth Truelstrup Hansen; Rob C. Jamieson. Fate of antibiotic resistance genes in two Arctic tundra wetlands impacted by municipal wastewater. Science of The Total Environment 2018, 642, 1415 -1428.

AMA Style

Jennifer L. Hayward, Amy J. Jackson, Christopher K. Yost, Lisbeth Truelstrup Hansen, Rob C. Jamieson. Fate of antibiotic resistance genes in two Arctic tundra wetlands impacted by municipal wastewater. Science of The Total Environment. 2018; 642 ():1415-1428.

Chicago/Turabian Style

Jennifer L. Hayward; Amy J. Jackson; Christopher K. Yost; Lisbeth Truelstrup Hansen; Rob C. Jamieson. 2018. "Fate of antibiotic resistance genes in two Arctic tundra wetlands impacted by municipal wastewater." Science of The Total Environment 642, no. : 1415-1428.

Journal article
Published: 01 October 2018 in FACETS
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Wastewater treatment plants (WWTPs) have been identified as hotspots for antimicrobial resistance genes (ARGs) and thus represent a critical point where patterns in ARG abundances can be monitored prior to their release into the environment. The aim of the current study was to measure the impact of the release of the final treated effluent (FE) on the abundance of ARGs in the receiving water of a recently upgraded WWTP in the Canadian prairies. Sample nutrient content (phosphorous and nitrogen species) was measured as a proxy for WWTP functional performance, and quantitative PCR (qPCR) was used to measure the abundance of eight ARGs, the intI1 gene associated with class I integrons, and the 16S rRNA gene. The genes ermB, sul1, intI1, blaCTX-M, qnrS, and tetO all had higher abundances downstream of the WWTP, consistent with the genes with highest abundance in the FE. These findings are consistent with the increasing evidence suggesting that human activity affects the abundances of ARGs in the environment. Although the degree of risk associated with releasing ARGs into the environment is still unclear, understanding the environmental dimension of this threat will help develop informed management policies to reduce the spread of antibiotic resistance and protect public health.

ACS Style

Claire N. Freeman; Lena Scriver; Kara D. Neudorf; Lisbeth Truelstrup Hansen; Rob C. Jamieson; Christopher Yost. Antimicrobial resistance gene surveillance in the receiving waters of an upgraded wastewater treatment plant. FACETS 2018, 3, 128 -138.

AMA Style

Claire N. Freeman, Lena Scriver, Kara D. Neudorf, Lisbeth Truelstrup Hansen, Rob C. Jamieson, Christopher Yost. Antimicrobial resistance gene surveillance in the receiving waters of an upgraded wastewater treatment plant. FACETS. 2018; 3 (1):128-138.

Chicago/Turabian Style

Claire N. Freeman; Lena Scriver; Kara D. Neudorf; Lisbeth Truelstrup Hansen; Rob C. Jamieson; Christopher Yost. 2018. "Antimicrobial resistance gene surveillance in the receiving waters of an upgraded wastewater treatment plant." FACETS 3, no. 1: 128-138.

Journal article
Published: 01 September 2018 in Journal of Environmental Quality
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The increasing prevalence of antibiotic resistance genes (ARGs) in the environment is problematic due to the risk of horizontal gene transfer and development of antibiotic resistant pathogenic bacteria. Using a suite of monitoring tools, this study aimed to investigate the sources of ARGs in a rural river system in Nova Scotia, Canada. The monitoring program specifically focused on the relative contribution of ARGs from a single tertiary-level wastewater treatment plant (WWTP) in comparison to contributions from the upgradient rural, sparsely developed, watershed. The overall gene concentration significantly (p < 0.05) increased downstream from the WWTP, suggesting that tertiary-level treatment still contributes ARGs to the environment. As a general trend, ARG concentrations upstream were found to decrease as proximity to human-impacted areas decreased; however, many ARGs remained above detection limits in headwater river samples, which suggested their ubiquitous presence in this watershed in the absence of obvious pollution sources. Significant correlations with ARGs were found for HF183 human fecal marker, Escherichia coli, and some antibiotics, suggesting that these markers may be useful for prediction and understanding of ARG levels and sources in rural rivers. Copyright © 2018. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

ACS Style

Mandy M. McConnell; Lisbeth Truelstrup Hansen; Kara D. Neudorf; Jenny L. Hayward; Rob C. Jamieson; Christopher Yost; Anthony Tong. Sources of Antibiotic Resistance Genes in a Rural River System. Journal of Environmental Quality 2018, 47, 997 -1005.

AMA Style

Mandy M. McConnell, Lisbeth Truelstrup Hansen, Kara D. Neudorf, Jenny L. Hayward, Rob C. Jamieson, Christopher Yost, Anthony Tong. Sources of Antibiotic Resistance Genes in a Rural River System. Journal of Environmental Quality. 2018; 47 (5):997-1005.

Chicago/Turabian Style

Mandy M. McConnell; Lisbeth Truelstrup Hansen; Kara D. Neudorf; Jenny L. Hayward; Rob C. Jamieson; Christopher Yost; Anthony Tong. 2018. "Sources of Antibiotic Resistance Genes in a Rural River System." Journal of Environmental Quality 47, no. 5: 997-1005.

Journal article
Published: 01 June 2018 in Journal of Environmental Engineering
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Presented here is a mechanistic model of the biological dynamics of the photic zone of a single-cell arctic waste stabilization pond (WSP) for the prediction of oxygen concentration and the removal of oxygen-demanding substances. The model is an exploratory model to assess the limiting environmental factors affecting treatment performance in arctic WSPs. A sensitivity analysis was used to provide a quantification of the relative uncertainties of parameters that exist within the described modeling framework. The model was able to qualitatively reproduce mesocosm experiment trends in phytoplankton growth, dissolved oxygen concentration, and the reduction of carbonaceous biochemical oxygen demand on Day 5 (CBOD5). These results demonstrated that CBOD5 reduction and oxygen state are very sensitive to organic loading regimes at low temperatures (5–15°C). The sensitivity analysis identified that it was the difference in phytoplankton growth rates, and the associated change in photosynthetic oxygen production, that mainly contribute to creating differences in CBOD5 removal rates and the development of aerobic conditions. The model was also sensitive to atmospheric aeration rates at low temperature, providing further evidence that low oxygen availability limits the treatment of CBOD5 in cold-climate WSPs. During the development process, it was discovered that common formulations of depth-integrated phytoplankton growth performed poorly for the arctic system to be modeled, which was a quiescent eutrophic environment. This paper presents a new phytoplankton growth formula within the paradigm of a poorly mixed eutrophic system that may find utilization in other eutrophic, colored, or turbid systems. The novel aspect of the approach is that the depth-integrated phytoplankton growth function was formulated upon the premise that the phytoplankton would be capable of orienting themselves to optimize their growth under poorly mixed conditions, and the average growth rate of the phytoplankton population must decrease as crowding puts pressure on shared resources. The general agreement of the model with the experiments, combined with the simplicity of the depth-integrated box model, suggests there is potential for further development of the model as a tool for assessing proposed arctic WSP designs. The sensitivity analysis highlighted the uncertainty and importance of the parameterization of bacterial and phytoplankton physiology and metabolism in WSP models.

ACS Style

Colin M. Ragush; Wendy C. Gentleman; Lisbeth Truelstrup-Hansen; Rob C. Jamieson. Operational Limitations of Arctic Waste Stabilization Ponds: Insights from Modeling Oxygen Dynamics and Carbon Removal. Journal of Environmental Engineering 2018, 144, 04018038 .

AMA Style

Colin M. Ragush, Wendy C. Gentleman, Lisbeth Truelstrup-Hansen, Rob C. Jamieson. Operational Limitations of Arctic Waste Stabilization Ponds: Insights from Modeling Oxygen Dynamics and Carbon Removal. Journal of Environmental Engineering. 2018; 144 (6):04018038.

Chicago/Turabian Style

Colin M. Ragush; Wendy C. Gentleman; Lisbeth Truelstrup-Hansen; Rob C. Jamieson. 2018. "Operational Limitations of Arctic Waste Stabilization Ponds: Insights from Modeling Oxygen Dynamics and Carbon Removal." Journal of Environmental Engineering 144, no. 6: 04018038.

Journal article
Published: 01 November 2017 in Science of The Total Environment
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Domestic wastewater discharges may adversely impact arctic ecosystems and local indigenous people, who rely on being able to hunt and harvest food from their local environment. Therefore, there is a need to develop efficient wastewater treatment plants (WWTPs), which can be operated in remote communities under extreme climatic conditions. WWTPs have been identified as reservoirs of antibiotic resistance genes (ARGs). The objective of this work was to quantify the presence of nine different ARG markers (int1, sul1, sul2, tet(O), erm(B), mecA, bla, bla, and qnr(S)) in two passive systems (waste stabilization ponds [WSPs]) and one mechanical filtration plant operating in two smaller and one large community, respectively, in Nunavut, Canada. Measurement of water quality parameters (carbonaceous oxygen demand, ammonia, total suspended solids, Escherichia coli and total coliforms) showed that the WWTPs provided only primary treatment. Low levels of the ARGs (2logcopies/mL) were observed in the effluent, demonstrating that bacteria residing in three northern WWTPs harbour ARGs conferring resistance to multiple clinically-relevant classes of antibiotics. Our results indicate that long-term storage in WSPs benefitted removal of organic material and some ARGs. However, one WSP system showed evidence of the enrichment of sul1, sul2, mecA, tet(O) and qnr(S). Further research is needed to fully understand if these ARG releases pose a risk to human health, especially in the context of traditional hunting and fishing activities.

ACS Style

Kara D. Neudorf; Yan Nan Huang; Colin M. Ragush; Christopher Yost; Rob C. Jamieson; Lisbeth Truelstrup Hansen. Antibiotic resistance genes in municipal wastewater treatment systems and receiving waters in Arctic Canada. Science of The Total Environment 2017, 598, 1085 -1094.

AMA Style

Kara D. Neudorf, Yan Nan Huang, Colin M. Ragush, Christopher Yost, Rob C. Jamieson, Lisbeth Truelstrup Hansen. Antibiotic resistance genes in municipal wastewater treatment systems and receiving waters in Arctic Canada. Science of The Total Environment. 2017; 598 ():1085-1094.

Chicago/Turabian Style

Kara D. Neudorf; Yan Nan Huang; Colin M. Ragush; Christopher Yost; Rob C. Jamieson; Lisbeth Truelstrup Hansen. 2017. "Antibiotic resistance genes in municipal wastewater treatment systems and receiving waters in Arctic Canada." Science of The Total Environment 598, no. : 1085-1094.

Comparative study
Published: 01 September 2017 in International Journal of Food Microbiology
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Listeria monocytogenes is a pathogenic foodborne microorganism noted for its ability to survive in the environment and food processing facilities. Survival may be related to the phenotype of individual strains including the ability to form biofilms and resist desiccation and/or sanitizer exposure. The objectives of this research were to compare 14 L. monocytogenes strains isolated from blood (3), food (6) and water (5) with respect to their benzalkonium chloride (BAC) sensitivity, desiccation resistance, and ability to form biofilm. Correlations were tested between those responses, and the presence of the SSI-1 (Stress Survival Islet) and LGI1/CC8 (Listeria Genomic Island 1 in a clonal complex 8 background) genetic markers. Genetic sequences from four strains representing different phenotypes were also probed for predicted amino acid differences in biofilm, desiccation, and membrane related genes. The water isolates were among the most desiccation susceptible strains, while strains exhibiting desiccation resistance harboured SSI-1 or both the SSI-1 and LGI1/CC8 markers. BAC resistance was greatest in planktonic LGI1/CC8 cells (relative to non-LGI1/CC8 cells), and higher BAC concentrations were also needed to inhibit the formation of biofilm by LGI1/CC8 strains during incubation for 48h and 6days compared to other strains. Formation of biofilm on stainless steel was not significantly (p>0.05) different among the strains. Analysis of genetic sequence data from desiccation and BAC sensitive (CP4 5-1, CP5 2-3, both from water), intermediate (Lm568, food) and desiccation and BAC resistant (08 5578, blood, human outbreak) strains led to the finding of amino acid differences in predicted functional protein domains in several biofilm, desiccation and peptidoglycan related genes (e.g., lmo0263, lmo0433, lmo0434, lmo0771, lmo0973, lmo1080, lmo1224, lmo1370, lmo1744, and lmo2558). Notably, the LGI1/CC8 strain 08-5578 had a frameshift mutation in lmo1370, a gene previously associated with desiccation resistance. In conclusion, the more desiccation and BAC resistant LGI1/CC8 isolates may pose a challenge for sanitation efforts.

ACS Style

Marta J. Piercey; Timothy C. Ells; Andrew J. Macintosh; Lisbeth Truelstrup Hansen. Variations in biofilm formation, desiccation resistance and Benzalkonium chloride susceptibility among Listeria monocytogenes strains isolated in Canada. International Journal of Food Microbiology 2017, 257, 254 -261.

AMA Style

Marta J. Piercey, Timothy C. Ells, Andrew J. Macintosh, Lisbeth Truelstrup Hansen. Variations in biofilm formation, desiccation resistance and Benzalkonium chloride susceptibility among Listeria monocytogenes strains isolated in Canada. International Journal of Food Microbiology. 2017; 257 ():254-261.

Chicago/Turabian Style

Marta J. Piercey; Timothy C. Ells; Andrew J. Macintosh; Lisbeth Truelstrup Hansen. 2017. "Variations in biofilm formation, desiccation resistance and Benzalkonium chloride susceptibility among Listeria monocytogenes strains isolated in Canada." International Journal of Food Microbiology 257, no. : 254-261.

Research article
Published: 29 June 2017 in PLOS ONE
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The human pathogen Listeria monocytogenes continues to pose a challenge in the food industry, where it is known to contaminate ready-to-eat foods and grow during refrigerated storage. Increased knowledge of the cold-stress response of this pathogen will enhance the ability to control it in the food-supply-chain. This study utilized strand-specific RNA sequencing and whole cell fatty acid (FA) profiling to characterize the bacterium’s cold stress response. RNA and FAs were extracted from a cold-tolerant strain at five time points between early lag phase and late stationary-phase, both at 4°C and 20°C. Overall, more genes (1.3×) were suppressed than induced at 4°C. Late stationary-phase cells exhibited the greatest number (n = 1,431) and magnitude (>1,000-fold) of differentially expressed genes (>2-fold, p<0.05) in response to cold. A core set of 22 genes was upregulated at all growth phases, including nine genes required for branched-chain fatty acid (BCFA) synthesis, the osmolyte transporter genes opuCBCD, and the internalin A and D genes. Genes suppressed at 4°C were largely associated with cobalamin (B12) biosynthesis or the production/export of cell wall components. Antisense transcription accounted for up to 1.6% of total mapped reads with higher levels (2.5×) observed at 4°C than 20°C. The greatest number of upregulated antisense transcripts at 4°C occurred in early lag phase, however, at both temperatures, antisense expression levels were highest in late stationary-phase cells. Cold-induced FA membrane changes included a 15% increase in the proportion of BCFAs and a 15% transient increase in unsaturated FAs between lag and exponential phase. These increases probably reduced the membrane phase transition temperature until optimal levels of BCFAs could be produced. Collectively, this research provides new information regarding cold-induced membrane composition changes in L. monocytogenes, the growth-phase dependency of its cold-stress regulon, and the active roles of antisense transcripts in regulating its cold stress response.

ACS Style

Patricia Hingston; Jessica Chen; Kevin Allen; Lisbeth Truelstrup Hansen; Siyun Wang. Strand specific RNA-sequencing and membrane lipid profiling reveals growth phase-dependent cold stress response mechanisms in Listeria monocytogenes. PLOS ONE 2017, 12, e0180123 -e0180123.

AMA Style

Patricia Hingston, Jessica Chen, Kevin Allen, Lisbeth Truelstrup Hansen, Siyun Wang. Strand specific RNA-sequencing and membrane lipid profiling reveals growth phase-dependent cold stress response mechanisms in Listeria monocytogenes. PLOS ONE. 2017; 12 (6):e0180123-e0180123.

Chicago/Turabian Style

Patricia Hingston; Jessica Chen; Kevin Allen; Lisbeth Truelstrup Hansen; Siyun Wang. 2017. "Strand specific RNA-sequencing and membrane lipid profiling reveals growth phase-dependent cold stress response mechanisms in Listeria monocytogenes." PLOS ONE 12, no. 6: e0180123-e0180123.