Progress 10/27/17 to 09/30/18
Outputs
Target Audience:The target audience for this research is the artisan cheesemaking community in the United States, although research fundings could apply to cheesemakers across the globe. The target audience in the U.S. with whom we work are small scale artisan cheesemakers who have limited access to technical and scientificresources. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project provided training for 4 graduate students, three M.S. and 1 Ph.D. These sudents were able to master environmental sampling techniques and learn microbiological methods for Listeria detection in dairy processing environments. Additionally, 2 graduate students were able to present the results of thier research at a national professional meeting. How have the results been disseminated to communities of interest?Results were presented at the Annual Meeting of the International Associationfor Food Protection in Salt Lake City. An abstract of this work was published, and a manuscript has been prepared for publication. What do you plan to do during the next reporting period to accomplish the goals?The artisan cheese industry in North America presents a multitude of research opportunities in food safety due to increased growth of the industry and the variety of production levels and cheese styles within the industry (Sauders and D'Amico, 2016). While this growth results in greater diversity of products and creates exciting opportunities for cheesemakers and consumers alike, it challenges regulators and food scientists to develop pathogen monitoring and control methods to match changes within the industry (Buchanan et al., 2017). In particular, the increased popularity of washed-rind, or smear-ripened, cheeses by small-scale producers suggests a need for validated cleaning protocols for specialized equipment used in smear-ripened cheese production. Boldyreva et al. (2016) report washed-rind cheeses as belonging to a group considered high risk for Listeria growth and describe multiple points for contamination of Listeria monocytogenes during post-production cheese care. This is illustrated through "old-young smearing," a practice often utilized in traditional washed-rind cheese production, whereby older cheeses are washed before newly made cheeses to carry bacteria and microflora from established cheese rinds to the young rinds to help influence the ripening process (Boldyreva et al., 2016). Although this process encourages rind development on young cheese and inoculates fresh cheese rinds with an established bacterial community, it presents the risk of cross contamination between batches and can result in the contamination of an otherwise safe cheese with pathogenic bacteria sourced from an older cheese (Schvartzman et al., 2014). Additionally, even when a stringent cross-contamination program is in place, tools and equipment used for washing smear-ripened cheese can hold on to bacteria in hard-to-clean places creating the potential for contamination, as seen in recent Listeria monocytogenes recalls in California and New York State where contaminated brushes were implicated as the source of the outbreak strain (D'Amico, D.J., Wiedmann, M., Doughty, 2016; Food and Drug Administration, 2017). Recent Listeria monocytogenes cases in the United States involving washed-rind cheeses are not the first evidence of brushes providing the source of the pathogen, however. The second major outbreak to take place in the last 50 years occurred in Switzerland between 1983 and 1987 resulting in 122 listeriosis cases leading to 34 deaths; the outbreak strains were ultimately linked back to the shelving and brushes used to care for Vacherin Mont d'Or cheese in ageing caves (Donnelly, 2004; Ryser, 2002). Similarly, Almeida et al. (2013) recorded a disproportionately high number of sampling sites positive for Listeria monocytogenes from the cheese washing station at a small-scale cheese production facility in Portugal. The same PFGE pattern was identified on wheels of cheese, brushes used to wash the cheese, and from the surfaces and floor areas at the cheese washing station, and the findings implicated the cheese brushes as playing a key role in the transfer of Listeria monocytogenes across different batches of cheese (Almeida et al., 2013). These findings are consistent with the idea that cross-contamination of Listeria monocytogenes in washed-rind cheeses occurring post-production via shared tools and equipment presents one of the greatest threats to human food safety (Jacquet et al., 1993). The background and significance of Listeria monocytogenes contamination in washed-rind cheeses indicates an opportunity for further research in this area. Brushes used for washing cheese have the potential to transport pathogens across batches of cheese if an appropriate cross-contamination program is lacking from a facility, however without adequate cleaning protocols, brushes also provide small niches and crevices that can accumulate food residues and support the growth of harmful bacteria (In Lee et al., 2017). Further research in the area of brushes used for washed-rind cheese may be essential in understanding current risks posed by washing practices in the artisan industry, while providing the opportunity for establishing specific hygiene methods and training materials to educate cheesemakers on the potential risks cheese-washing brushes pose. A validated cleaning protocol for brushes can assist cheesemakers in eliminating cheese-washing brushes as potential vectors for Listeria monocytogenes transmission in cheese production.
Impacts
What was accomplished under these goals?
Preventing Listeria contamination of artisan cheese requires routine and effective environmental monitoring of product contact surfaces within the production environment. The sensitivity of environmental monitoring methods is essential when testing for the presence of Listeria spp. within the processing environment as a way to control the risk of cheese contamination. Four environmental surfaces (dairy brick, stainless steel, plastic, and wood; n=216 surface type) were inoculated with L. innocua (Green Fluorescent Protein), L.m. ATTC® 19115 and L.m. 1042B, at high (106-107 cfu/cm2) and low (0.01-1 cfu/cm2) target concentrations. Inoculated surfaces were swabbed with World Bioproducts© EZ ReachTM environmental swabs with HiCap (WBHC) and Dey-Engley (WBDE) neutralizing broths, and 3MTM environmental swabs (3MTM) with Dey-Engley neutralizing broth. 3MTM Listeria Environmental Plate and Aerobic Plate Count Petrifilm enumeration methods and FDA, modified FDA, dual MOPS-BLEB enrichment, and modified USDA enrichment methods were used to compare sensitivity of recovery between environmental swabs. When applied at low concentrations, 3MTM, WBDE, and WBHC swabs recovered Listeria spp. from 90.9%, 88.4% and 83.2% of plastic, stainless steel, and dairy brick surfaces, respectively, but only 65.7% of wooden surfaces; recovering 14.8%, 77%, and 96.3% at 0.01, 0.1, and 1 cfu/cm2, respectively (p<0.05). Slight differences in recovery (84.8% for WBDE, 78.1% for WBHC, and 80.9% for 3MTM) for all surfaces were observed. Variable recovery was influenced by strain, where L.m. 1042B was recovered more effectively from wooden surfaces by 3MTM, WBDE, and WBHC swabs, followed by L.m. 19115, and lastly L. innocua. Equivalent performance between swab formats was observed for all tested surfaces except wood, therefore porosity of environmental surfaces should be taken into consideration when implementing environmental sampling plans
Publications
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2018
Citation:
Limoges, M., G. Frontino and C. Donnelly. 2018. Comparative Recovery of Listeria spp. from Dairy Environmental Surfaces Using 3M and World Bioproducts Environmental Sponges and Standard Enrichment and Enumeration Methods. P3-148. IAFP Annual Meeting, Salt Lake City, UT July 7-11.
|