In the EU, food is considered safe with regard to Listeria monocytogenes if its numbers do not exceed 100 CFU/g throughout the shelf-life of the food. Therefore, it is important to determine if a food supports growth of L. monocytogenes. Challenge studies to determine the ability of a food to support growth of L. monocytogenes are essential as predictive modelling often overestimates the growth ability of L. monocytogenes. The aim of this study was to determine if growth of L. monocytogenes was supported during the production and distribution of mushrooms. A three-strain mixture of L. monocytogenes was inoculated onto three independent batches of whole mushrooms, sliced mushrooms, mushroom casing and mushroom substrate at a concentration of about 100–1000 CFU/g. The batches were incubated at potential abuse temperatures, as a worst case scenario, and at intervals during storage L. monocytogenes numbers, % moisture and pH were determined. The results showed that the sliced and whole mushrooms had the ability to support growth, while mushroom casing allowed survival but did not support growth. Mushroom substrate showed a rich background microflora that grew on Listeria selective media and this hindered enumeration of L. monocytogenes. In the case of this study, Combase predictions were not always accurate, indicating that challenge studies may be a necessary part of growth determination of L. monocytogenes.
References
[1]
Gerner-Smidt, P.; Ethelberg, S.; Schiellerup, P.; Christensen, J.J.; Engberg, J.; Fussing, V.; Jensen, A.; Jensen, C.; Petersen, A.M.; Bruun, B.G. Invasive listeriosis in Denmark 1994–2003: A review of 299 cases with special emphasis on risk factors for mortality. Clin. Microbiol. Infect. 2005, 11, 618–624.
Wang, X.-M.; Lü, X.-F.; Yin, L.; Liu, H.-F.; Zhang, W.-J.; Si, W.; Yu, S.-Y.; Shao, M.-L.; Liu, S.-G. Occurrence and antimicrobial susceptibility of Listeria monocytogenes isolates from retail raw foods. Food Control 2013, 32, 153–158.
[4]
Cartwright, E.J.; Jackson, K.A.; Johnson, S.D.; Graves, L.M.; Silk, B.J.; Mahon, B.E. Listeriosis outbreaks and associated food vehicles, united states, 1998–2008. Emerg. Infect. Dis. 2013, 19, 1–9.
[5]
European Food Safety Authority; European Centre for Disease Prevention and Control. The European Union Summary Report on Trends and Sources of Zoonoses, Zoonotic Agents and Food-Borne Outbreaks in 2011. TEFSA J. 2013, 11, 3129.
[6]
Guidance Document on Listeria monocytogenes Shelf-Life Studies for Ready-To-Eat Foods, under Regulation (EC) No 2073/2005 of 15 November 2005 on Microbiological Criteria for foodstuffs. Available online: http://ec.europa.eu/food/food/biosafety/salmonella/docs/guidoc_listeria_monocytogenes_en.pdf (accessed on 22 November 2013).
[7]
Rosshaug, P.S.; Detmer, A.; Ingmer, H.; Larsen, M.H. Modeling the growth of Listeria monocytogenes in soft blue-white cheese. Appl. Environ. Microbiol. 2012, 78, 8508–8514.
[8]
Powell, M.R. Analyzing the power and error of Listeria monocytogenes growth challenge studies. Int. J. Food Microbiol. 2009, 136, 10–17.
[9]
Schvartzman, M.S.; Belessi, C.; Butler, F.; Skandamis, P.N.; Jordan, K.N. Effect of pH and water activity on the growth limits of Listeria monocytogenes in a cheese matrix at two contamination levels. J. Food Prot. 2011, 74, 1805–1813.
[10]
Viswanath, P.; Murugesan, L.; Knabel, S.J.; Verghese, B.; Chikthimmah, N.; Laborde, L.F. Incidence of Listeria monocytogenes and Listeria spp. in a small-scale mushroom production facility. J. Food Prot. 2013, 76, 608–615, doi:10.4315/0362-028X.JFP-12-292.
[11]
Venturini, M.E.; Reyes, J.E.; Rivera, C.S.; Oria, R.; Blanco, D. Microbiological quality and safety of fresh cultivated and wild mushrooms commercialized in Spain. Food Microbiol. 2011, 28, 1492–1498.
[12]
Agency, C.F.I. Health Hazard Alert—Certain SLICED WHITE MUSHROOMS May Contain Listeria monocytogenes. Available online: http://www.inspection.gc.ca/about-the-cfia/newsroom/food-recall-warnings/complete-listing/2012–08–13/eng/1355956870790/1355956870806 (accessed on 22 November 2013).
[13]
González-Fandos, E.; Olarte, C.; Giménez, M.; Sanz, S.; Simón, A. Behaviour of Listeria monocytogenes in packaged fresh mushrooms (Agaricus bisporus). J. Appl. Microbiol. 2001, 91, 795–805, doi:10.1046/j.1365-2672.2001.01452.x.
[14]
Everis, L.; Betts, G. Evaluation of listeria challenge testing protocols: A practical study using cooked sliced ham. Food Control 2013, 29, 61–65, doi:10.1016/j.foodcont.2012.06.010.
[15]
ComBase. Available online: http://modelling.Combase.Cc/membership/combaselogin.Aspx?Returnurl=%2fdmfit.Aspx (accessed on 9 September 2013).
[16]
Baranyi, J.; Roberts, T.A. A dynamic approach to predicting bacterial growth in food. Int. J. Food Microbiol. 1994, 23, 277–294, doi:10.1016/0168-1605(94)90157-0.
[17]
Xi, Y.; Sullivan, G.A.; Jackson, A.L.; Zhou, G.H.; Sebranek, J.G. Effects of natural antimicrobials on inhibition of Listeria monocytogenes and on chemical, physical and sensory attributes of naturally-cured frankfurters. Meat Sci. 2012, 90, 130–138.
[18]
Liserre, A.M.; Landgraf, M.; Destro, M.T.; Franco, B.D.G.M. Inhibition of Listeria monocytogenes by a bacteriocinogenic Lactobacillus sake strain in modified atmosphere-packaged brazilian sausage. Meat Sci. 2002, 61, 449–455.
[19]
Hoelzer, K.; Pouillot, R.; Dennis, S. Listeria monocytogenes growth dynamics on produce: A review of the available data for predictive modeling. Foodborne Pathog. Dis. 2012, 9, 661–673, doi:10.1089/fpd.2011.1087.
