@article{escudero-abarca_rawsthorne_goulter_suh_jaykus_2014, title={Molecular methods used to estimate thermal inactivation of a prototype human norovirus: More heat resistant than previously believed?}, volume={41}, ISSN={["1095-9998"]}, DOI={10.1016/j.fm.2014.01.009}, abstractNote={Two molecular-based methods for estimating capsid integrity as a proxy for virus infectivity were used to produce thermal inactivation profiles of Snow Mountain virus (SMV), a prototype human norovirus (HuNoV). Monodispersed virus suspensions were exposed to 77, 80, 82 and 85 °C for various times, pre-treated with either propidium monoazide (PMA) or RNase, and subjected to RNA isolation followed by RT-qPCR amplification. D-values were 25.6 ± 2.8, 3.1 ± 0.1, 0.7 ± 0.04 and 0.2 ± 0.07 min at 77, 80, 82 and 85 °C, respectively for PMA-treated SMV; and 16.4 ± 0.4, 3.9 ± 0.2 0.9 ± 0.3 and 0.12 ± 0.00 min at 77, 80, 82 and 85 °C, respectively for RNase-treated SMV. Corresponding zD values were 3.80 °C and 3.71 °C for PMA and RNase-treated virus, respectively. Electron microscopy data applied to heat-treated virus-like particles supported this relatively high degree of thermal resistance. The data suggest that SMV is more heat resistant than common cultivable HuNoV surrogates. Standardized thermal inactivation methods (such as milk pasteurization) may not be stringent enough to eliminate this virus and perhaps other HuNoV.}, journal={FOOD MICROBIOLOGY}, author={Escudero-Abarca, B. I. and Rawsthorne, H. and Goulter, R. M. and Suh, S. H. and Jaykus, L. A.}, year={2014}, month={Aug}, pages={91–95} }
 @article{escudero_rawsthorne_gensel_jaykus_2012, title={Persistence and Transferability of Noroviruses on and between Common Surfaces and Foods}, volume={75}, ISSN={["1944-9097"]}, DOI={10.4315/0362-028x.jfp-11-460}, abstractNote={Human noroviruses (HuNoV) are the leading cause of foodborne disease, and poor personal hygiene practices of infected workers are the most common mode of contamination. The purpose of this study was to characterize the persistence and transferability of representative noroviruses Norwalk virus (NV), Snow Mountain virus (SMV), and murine norovirus 1 (MNV-1) on and between solid surfaces and foods. Changes in virus concentration on artificially inoculated solid surfaces (stainless steel, ceramic, and Formica) or lettuce were monitored over a period of 14 to 42 days. Virus transfer was evaluated from donor (solid surface) to recipient (food, e.g., lettuce and sliced turkey deli meat) for up to 2 h postinoculation. Viruses were recovered by elution and titered with reverse transcription quantitative PCR (RT-qPCR) and/or infectivity assay, as appropriate. Based on RTqPCR, the concentration of NV and SMV on surfaces dropped gradually over time, with an average reduction of 1.5 to 2.0 and 1.8 to 2.3 log, respectively, after 42 days, with no statistically significant differences by surface. When inoculated onto lettuce stored for 2 weeks at 4°C and room temperature, the titers of NV and SMV dropped by approximately 1.0 and 1.2 to 1.8 log, respectively. Comparatively, the RT-qPCR signal associated with purified HuNoV RNA placed on the same surfaces was more rapidly lost to degradation. Transfer efficiency ranged from 0 to 26 % for lettuce and from 55 to 95 % for sliced turkey deli meat, with statistically significant differences (P ≤ 0.05) in transferability as a function of contact pressure (100 and 1,000 g/9 cm(2)) and inoculum drying time. When similar experiments were done with MNV-1, infectious virus failed to be detected on solid surfaces after storage day 21, although the virus did persist on lettuce. This study provides much needed quantitative data for use in risk assessment efforts intended to characterize the transmission of HuNoV during food preparation and handling.}, number={5}, journal={JOURNAL OF FOOD PROTECTION}, author={Escudero, B. I. and Rawsthorne, H. and Gensel, C. and Jaykus, L. A.}, year={2012}, month={May}, pages={927–935} }
 @article{gray_rawsthorne_dirks_phister_2011, title={Detection and enumeration of Dekkera anomala in beer, cola, and cider using real-time PCR}, volume={52}, ISSN={["1472-765X"]}, DOI={10.1111/j.1472-765x.2011.03008.x}, abstractNote={Aims:  In this article, a quantitative real‐time PCR assay for detection and enumeration of the spoilage yeast Dekkera anomala in beer, cola, apple cider, and brewing wort is presented as an improvement upon existing detection methods, which are very time‐consuming and not always accurate.}, number={4}, journal={LETTERS IN APPLIED MICROBIOLOGY}, author={Gray, S. R. and Rawsthorne, H. and Dirks, B. and Phister, T. G.}, year={2011}, month={Apr}, pages={352–359} }
 @article{rawsthorne_phister_2009, title={Detection of viable Zygosaccharomyces bailii in fruit juices using ethidium monoazide bromide and real-time PCR}, volume={131}, ISSN={["1879-3460"]}, DOI={10.1016/j.ijfoodmicro.2009.01.031}, abstractNote={In this study, we use ethidium monoazide (EMA) a dye commonly used to differentiate viable and nonviable populations of bacteria in real-time PCR (QPCR) assays to eliminate the nonviable cells from the Z. bailii population. Thus we are able to determine the viable Z. bailii population using QPCR plus EMA. To do this we first, optimized the EMA exposure conditions; EMA concentration of 50 microg/ml with an incubation at 30 degrees C in the dark for 5 min. Followed by light exposure on ice, for 5 min using a 500 W halogen lamp at a distance of 12 cm. Using these optimized conditions, we determined that the assay could detect as few as 12.5 viable Z. bailii cells in the presence of 10(5) CFU/ml of heat killed-cells. The EMA assay was also more consistent at determining viable cell counts when compared to plating than fluorescent microscopy viable cell counts. Finally, we used the assay to determine the viable population in heat-treated (72 degrees C, 2 min), ethanol-treated and raspberry cranberry juice Z. bailii cultures. When examining Z. bailii cells treated with 70% ethanol the QPCR assay with EMA (1.22 x 10(2)) showed a better correlation with plating (4.5 x 10(1) CFU/ml) compared to the QPCR assay without EMA (5.31 x 10(6) CFU/ml) and this was also seen in the other two injured populations. Thus we feel that we have designed an assay which will be useful for the detection of viable spoilage yeasts in various fruit juices.}, number={2-3}, journal={INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY}, author={Rawsthorne, Helen and Phister, Trevor G.}, year={2009}, month={May}, pages={246–250} }
 @article{rawsthorne_phister_jaykus_2009, title={Development of a Fluorescent In Situ Method for Visualization of Enteric Viruses}, volume={75}, ISSN={["1098-5336"]}, DOI={10.1128/AEM.01986-09}, abstractNote={ABSTRACT}, number={24}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, author={Rawsthorne, Helen and Phister, Trevor G. and Jaykus, Lee-Ann}, year={2009}, month={Dec}, pages={7822–7827} }
 @article{rawsthorne_dock_jaykus_2009, title={PCR-Based Method Using Propidium Monoazide To Distinguish Viable from Nonviable Bacillus subtilis Spores}, volume={75}, ISSN={["0099-2240"]}, DOI={10.1128/AEM.02524-08}, abstractNote={ABSTRACT}, number={9}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, author={Rawsthorne, H. and Dock, C. N. and Jaykus, L. A.}, year={2009}, month={May}, pages={2936–2939} }
 @article{rawsthorne_phister_2009, title={The presence of Saccharomyces cerevisiae DNA in various media used to propagate yeasts and its removal by ethidium monoazide}, volume={49}, ISSN={["1472-765X"]}, DOI={10.1111/j.1472-765X.2009.02707.x}, abstractNote={Aims:  In this study we demonstrate the interference of yeast extract in enumeration of Saccharomyces cerevisiae using real‐time PCR and develop a method for its removal from the media using ethidium monoazide (EMA).}, number={5}, journal={LETTERS IN APPLIED MICROBIOLOGY}, author={Rawsthorne, H. and Phister, T. G.}, year={2009}, month={Nov}, pages={652–654} }
 @article{sela_rawsthorne_mills_2007, title={Characterization of the lactococcal group II intron target site in its native host}, volume={58}, ISSN={["1095-9890"]}, DOI={10.1016/j.plasmid.2007.02.003}, abstractNote={The Lactococcus lactis group II intron (Ll.ltrB) retrohomes into the ltrB gene at high efficiency. To date, the critical DNA bases recognized in vivo by the Ll.ltrB ribonucleoprotein (RNP) have been exclusively elucidated in Escherichia coli. However, recent evidence indicates host-dependant differences in Ll.ltrB mobility, raising the possibility of limitations of the current model for RNP-homing site recognition in the native L. lactis host. In this work, intron retargeting experiments in L. lactis have demonstrated that adherence to specific target site critical bases is not sufficient to predict success or failure of chromosomal invasion, as in E. coli. Accordingly, a quantitative real-time PCR (QPCR) assay was developed to test target site nucleotides previously demonstrated as critical for homing in E. coli, for relevance in its native host. This two-plasmid QPCR homing assay is highly sensitive and, unlike previous E. coli-based assays, resolves differential homing efficiencies in the absence of selection. As in E. coli, deviation from wild type at target site positions −23, −21, −20, −19, and +5 resulted in lower homing efficiencies in L. lactis. Furthermore, the same trends are observed when assaying select variants in Enterococcus faecalis. Our results suggest that these target site positions are critical in both E. coli and L. lactis.}, number={2}, journal={PLASMID}, author={Sela, David A. and Rawsthorne, Helen and Mills, David A.}, year={2007}, month={Sep}, pages={127–139} }