Research Projects
Current Projects
Cleaning and sanitizing surfaces on produce farms: optimizing what, how, and when
First year of inspections on produce farms covered by the Produce Safety Rule (PSR) highlighted that farms fall short of regulators’ expectations for postharvest and harvest sanitation practices. The expectation is that farms will have the knowledge and resources to implement appropriate cleaning and sanitizing practices (CSPs) for various surface types encountered in produce settings. However, there is a lack of training on how to correctly implement appropriate CSPs and document them as part of validation and verification activities, exacerbated by a lack of methods for evaluating the performance of CSPs on diverse food contact surfaces (FCSs) in produce farm settings. To provide produce industry with data on best CSPs to meet PSR requirements, this project will: (i) engage with produce industry to collect information on the diversity of FCSs in their operations and characterize CSPs; (ii) quantify the “real-world” organic and microbial loads of FCSs before and after cleaning and sanitizing on produce farms; (iii) evaluate the efficacy of CSPs for challenging surfaces (e.g., foam, brushes), and optimize these procedures for each surface type; and (iv) train produce growers to implement effective CSPs and verify the effectiveness of these procedures through environmental monitoring programs. Through coordinated research and extension efforts, planned activities will utilize applied science and extension activities to help produce industry better implement cleaning and sanitizing programs to mitigate microbial risks and achieve compliance with PSR.
Exploration of the genetic diversity of Listeria monocytogenes recovered from British Columbia dairy facilities over a 10-year sampling initiative
In response to two listeriosis outbreaks in British Columbia (Canada) linked to soft cheeses, a voluntary monthly testing of soft/mould-ripened cheeses and inspector-collected testing of environmental swabs for Listeria monocytogenes were introduced in 2003. These activities have helped assess prevalence of L. monocytogenes; however, there is a need to better understand strain characteristics, particularly those associated with persistent strains. The goal of this research is to understand contamination patterns and assess genomic diversity of L. monocytogenes isolates from BC dairy facilities collected though provincial dairy inspection system.
Analysis of Food Safety Modernization Act Produce Safety and Preventive Controls for Human Food trainings in the Western Region of the United States
The Western Regional Center to Enhance Food Safety (WRCEFS) is one of four U.S. regional centers that coordinates Food Safety Modernization Act (FSMA) food safety training programs in 13 states and two territories. Two types of trainings that are currently offered include grower trainings, available through the PSA, and Preventive Controls for Human Food trainings for preventive controls qualified individuals, available through the Food Safety Preventive Controls Alliance (FSPCA). The purpose of this work is to evaluate the knowledge gained by participants in both the PSA and FSPCA trainings in the western region.
Using Google Analytics to track WRCEFS website and resource activities
WRCEFS coordinates Food Safety Modernization Act food safety training programs and supports food safety trainers in 13 western states and 2 territories. Although WRCEFS has had an online presence through a website (https://agsci.oregonstate.edu/wrcefs) for several years, no data were available prior to 2020 to understand the Center’s regional and global reach and online engagement.
When the COVID-19 pandemic and Western U.S. wildfire and winter storm disasters occurred, food safety resources specific for these events were needed in the region. We created three webpages (https://agsci.oregonstate.edu/wrcefs/covid-19-resources, https://agsci.oregonstate.edu/wrcefs/article/food-safety-and-wildfires, and https://agsci.oregonstate.edu/wrcefs/article/food-safety-during-power-outages) addressing these topics. Webpages were promoted on social media and through university extension networks. The purpose of these two research projects is to identify the main audience of the WRCEFS website and resource pages and their interaction with the WRCEFS web-based platforms
As of April 9, 2021, there have been 5,094 COVID-19, 553 wildfire, and 62 power outage pageviews. Analytics data from these websites will help us improve messaging and dissemination of food safety information in future crisis situations.
Previous Projects
Enhancement of Produce Safety Alliance grower training curriculum through activities that increase participant engagement
The Produce Safety Rule requires that one individual from each produce farm subject to the rule attend a grower food safety training. Currently the Produce Safety Alliance (PSA) curriculum is the only FDA approved training to satisfy this rule requirement. The original, in-person PSA training is intended to be delivered as an 8-hour lecture-based course with limited opportunities for participant engagement. Trainers have the option to expand these trainings, as long as every slide is presented to course participants. Our team created and delivered a 1.5-day PSA workshop that incorporated additional learning activities in each module to increase participant engagement and learning. Pre- and post-tests and course evaluations from traditional and modified PSA courses were compared to determine if differences in knowledge gain between these two course styles exist.
The evaluation data from these modified courses and course details are detailed in an article recently published in Food Protection Trends.
Read more about this work here.
Alvarado, S., R. Bland, S. Brown, J. Waite-Cusic, J. Kovacevic*. 2022. Enhancement of Produce Safety Alliance grower training curriculum through activities that increase participant engagement. Food Protection Trends. 42(2):124-138 https://doi.org/10.4315/FPT-21-019
Investigation of cross-resistance development between commercial sanitizer and antibiotics in Listeria monocytogenes isolated from fresh produce environments
It has been previously observed that Listeria monocytogenes adapted to sanitizers such as quaternary ammonium compounds (QAC), result in reduced sensitivity towards some clinically relevant antibiotics. With the growing concern of L. monocytogenes contamination within the fresh produce industry and reliance on effective cleaning and sanitation to mitigate this risk, it is of upmost importance that this phenomenon, also known as cross-resistance, be further examined and environment isolates continuously monitored for changes in susceptibility. The goal of this work was to determine the potential for cross-resistance between a QAC based commercial sanitizer and antibiotics in 6 hypervirulent L. monocytogenes isolates obtained from environmental samples of produce handling and processing facilities in the Pacific Northwest. Data obtained in this study highlights the potential for cross-resistance between QAC and antibiotics; however, no cross-resistance between antibiotics typically used to treat listeriosis (e.g., amikacin, gentamicin) and QAC were observed, providing confidence in the continued use of these antibiotics as listeriosis treatment options.
Bland, R., Waite-Cusic, A. J. Weisberg, E. R. Riutta, J. H. Chang, and J. Kovacevic. 2022. Adaptation to a commercial quaternary ammonium compound sanitizer leads to cross-resistance to select antibiotics in Listeria monocytogenes isolated from fresh produce environments. Frontiers in Microbiology. 12(4059). https://doi.org/10.3389/fmicb.2021.782920
Read more about this work here.
Assessing the prevalence of antimicrobial resistance genes within Listeria monocytogenes isolates originating from produce handling and processing facilities
Listeria monocytogenes control within the fresh produce supply chain is reliant on effective cleaning and sanitation procedures to mitigate the potential risk of product contamination. Genetic elements such as efflux pumps are known to contribute to this risk by improving the tolerance of L. monocytogenes against antimicrobials such as quaternary ammonium compounds (QAC). Our lab is using whole genome sequencing to 1) assess genetic diversity through classifying clonal complexes (by Multi-Locus Sequence Typing; MLST) of 48 L. monocytogenes isolates obtained from produce handling and processing environments in the Pacific Northwest, and 2) identifying genetic elements such as efflux pumps that will provide insight into tolerance towards sanitizers used widely throughout the industry. As L. monocytogenes are common contaminants within produce handling and processing operations, it is critical to understand factors contributing to their survival or persistence within these environments.
Read more about this work here.
Bland, Rebecca N., J. D. Johnson, J. G. Waite-Cusic, A. J. Weisberg, E. R. Riutta, J. H. Chang, and J. Kovacevic. 2021. Application of Whole Genome Sequencing to Understand Diversity and Presence of Genes Associated with Sanitizer Tolerance in Listeria monocytogenes from Produce Handling Sources. Foods 10, no. 10: 2454.
Relative performance of commercial citric acid and quaternary ammonium sanitizers against Listeria monocytogenes under conditions relevant to
food industry
Growth of Listeria monocytogenes in cold temperatures coupled with its tolerance of antimicrobials can promote its survival and persistence in food processing environments. The food industry relies heavily on cleaning and sanitation to control L. monocytogenes.
The minimum bactericidal concentrations (MBCs) of an “eco-friendly” citric acid-based (CAB) sanitizer and a conventional quaternary ammonium compound (CQAC) sanitizer were determined against 14 L. monocytogenes isolates at 4–30 ◦C. A subset of isolates (n = 3) was also exposed to sub-lethal concentrations of sanitizers to assess differences in growth behavior. CAB and CQAC were effective at manufacturer recommended concentrations in liquid assays. The MBC of CAB was significantly lower at 4 ◦ C compared to 23 ◦ C (p < 0.05), whereas the MBC of CQAC was unchanged between 4 ◦ C and 23 ◦ C. Manufacturers’ recommendations for dose and duration of CAB and CQAC were unable to consistently achieve a >5-log reduction of L. monocytogenes attached to surfaces. Findings from this study demonstrate the importance of sanitizer evaluation under conditions representative of their use in the food industry.
Read more about this work here.
Boucher, C., J. Waite-Cusic, D. Stone, J. Kovacevic. (2021) Relative performance of commercial citric acid and quaternary ammonium sanitizers against Listeria monocytogenes under conditions relevant to
food industry. Food Microbiology, 97: 103752
Prevalence of Listeria spp. in produce handling and processing facilities in the Pacific Northwest
Listeria monocytogenes is a significant concern for the produce industry; however, there is limited information to support the practical decision-making to mitigate this risk.
This study investigated the prevalence of Listeria spp. and L. monocytogenes in seven produce handling and processing (PHP) facilities in the Pacific Northwest. PHP facilities were defined as facilities that receive raw agricultural commodities and further handle, pack, wash, or process prior to distribution into the retail sector. Environmental swabs (n = 50/facility) were collected in high- risk areas (e.g., near raw product entry points) from seven PHP facilities over two visits. Listeria spp., including L. monocytogenes, were found in 5/7 PHP. Prevalence of Listeria spp. ranged from 2% to 26% in these five facilities.
Drains, entry areas, and portable equipment consistently tested positive for Listeria spp. during active produc- tion. Two additional sampling rounds (n = 50/round) were conducted in the highest prevalence facility (Facility #1). Overall, Listeria spp. were detected in 44/150 (29.3%) swabs collected from Facility #1. This study demonstrated the high prevalence of Listeria spp. near raw product entry points across PHP facilities.
Read more about this work here.
Jorgensen, J., J. Waite-Cusic, J. Kovacevic. (2020) Prevalence of Listeria spp. in produce handling and processing facilities in the Pacific Northwest. Food Microbiology, 90: 103468 https://doi.org/10.1016/j.fm.2020.103468
Diversity and antimicrobial resistance of Listeria spp. and L. monocytogenes clones from produce handling and processing facilities in the
Pacific Northwest
The widespread nature of Listeria monocytogenes and its presence in soil and agricultural environments, make it a challenging pathogen to control in the produce industry. The objective of this study was to assess diversity of Listeria spp. isolates (n = 113) previously recovered from five produce handling and processing facilities in the Pacific Northwest, using molecular and antibiogram typing.
Most individual facilities contained a single serogroup of L. monocytogenes; two facilities were positive for serogroup 1 only and two facilities were positive for serogroup 4 only. The facility with the highest prevalence of Listeria spp. was positive for both serogroups. MLST identified 10 unique sequence types (STs) within 10 clonal complexes (CCs), with hypervirulent clones of CC2 and CC4 being overrepresented.
All Listeria spp. isolates were sensitive to ampicillin, erythromycin, gentamicin, imipenem, co- trimoxazole, tetracycline and vancomycin and resistant to cefoxitin and nalidixic acid. A high proportion (66%) of Listeria spp. isolates was resistant to clindamycin, whereas resistance to penicillin, ciprofloxacin, rifampin, and novobiocin was less common. Three L. monocytogenes isolates and one L. innocua isolate were multi-drug resistant (MDR; resistant to ≥3 antibiotics). While the majority of Listeria spp. remain sensitive to clinically relevant antibiotics, the presence of MDR in strains recovered from produce handling and processing environments is concerning and prompts further studies to understand the pressures driving the AMR changes in these microorganisms.
Read more about this work here.
Jorgensen, J., R. Bland, J. Waite-Cusic, J. Kovacevic. (2021) Diversity and antimicrobial resistance of Listeria spp. and L. monocytogenes clones from produce handling and processing facilities in the Pacific Northwest. Food Control, 123: 107665 https://doi.org/10.1016/j.foodcont.2020.107665
Recent Publications
| Bland, R., S. R. B. Brown, J. G. Waite-Cusic, J. Kovacevic#. 2022. Probing antimicrobial resistance and sanitizer tolerance themes and their implications for the food industry through the Listeria monocytogenes lens. Compr. Rev. Food Sci. Food Saf. 2022:1-26. https://doi.org/10.1111/1541-4337.12910 |
| Bland, R., Waite-Cusic, A. J. Weisberg, E. R. Riutta, J. H. Chang, and J. Kovacevic#. 2022. Adaptation to a commercial quaternary ammonium compound sanitizer leads to cross-resistance to select antibiotics in Listeria monocytogenes isolated from fresh produce environments. Front. Microbiol. 12(4059). https://doi.org/10.3389/fmicb.2021.782920 |
| Alvarado, S., R. Bland, S. Brown, J. Waite-Cusic, J. Kovacevic#. 2022. Enhancement of Produce Safety Alliance grower training curriculum through activities that increase participant engagement. Food Prot. Trends. 42(2):124-138 https://doi.org/10.4315/FPT-21-019 |
| Kovacevic, J. 2022. Development of add-on materials to supplement Food Safety Modernization Act trainings in the Western U.S. J. Extension. 60(1), Article 10. https://doi.org/10.34068/joe.60.01.11 |
| Bland, R., J. D. Johnson, J. G. Waite-Cusic, A. J. Weisberg, E. R. Riutta, J. H. Chang, and J. Kovacevic#. 2021. Application of whole genome sequencing to understand diversity and presence of genes associated with sanitizer tolerance in Listeria monocytogenes from produce handling sources. Foods. 10, no. 10: 2454. https://doi.org/10.3390/foods10102454 |
| Boucher, C., J. Waite-Cusic, D. Stone, J. Kovacevic#. 2021. Relative performance of commercial citric acid and quaternary ammonium sanitizers against Listeria monocytogenes under conditions relevant to food industry. Food Microbiol. 97(2021):103752. https://doi.org/10.1016/j.fm.2021.103752 |
| Jorgensen, J., R. Bland, J. Waite-Cusic, J. Kovacevic#. 2021. Diversity and antimicrobial resistance of Listeria spp. and L. monocytogenes clones from produce handling and processing facilities in the Pacific Northwest. Food Control 123(2021):107665. https://doi.org/10.1016/j.foodcont.2020.107665 |
| Jorgensen, J., J. Waite-Cusic, J. Kovacevic#. 2020. Prevalence of Listeria spp. in produce handling and processing facilities in the Pacific Northwest. Food Microbiol. 90(2020):103468. https://doi.org/10.1016/j.fm.2020.103468 |
| Stone, D., J. Kovacevic, S. Brown. 2020. Sanitizer basics for the food industry. PNW Pacific Northwest Extension Publishing. PNW 752. https://catalog.extension.oregonstate.edu/pnw752 |
