Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro Short communication Listeria monocytogenes colonization in a newly established dairy processing facility Beatriz Melero a , Beatrix Stessl b , Beatriz Manso a , Martin Wagner b , Óscar J. Esteban-Carbonero a , Marta Hernández a,c , Jordi Rovira a , David Rodriguez-Lázaro a, ⁎ a Department of Biotechnology and Food Science, University of Burgos, Burgos, Spain b Institute of Milk Hygiene, Milk Technology and Food Science, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Vienna, Austria c Laboratory of Molecular Biology and Microbiology, Instituto Tecnológico Agrario de Castilla y León, Valladolid, Spain ARTICLE INFO Keywords: Listeria monocytogenes Cheese Colonization Persistence ABSTRACT The presence and colonization of Listeria monocytogenes were investigated in a newly established dairy proces- sing plant during a one-year period. A total of 250 non-food contact surfaces, 163 food contact surfaces, 46 personnel and 77 food samples were analyzed in two different buildings according to the cheese production chain. Initial steps, including salting, are performed in building I (old facility), while the final steps, including ripening, cutting and packaging, are performed in building II (new facility). Overall, 218 samples were collected from building I and 318 from building II. L. monocytogenes isolates were subtyped by PFGE and MLST, and a questionnaire about quality measures was completed. The overall prevalence of L. monocytogenes was 8.40%, and while the presence of the pathogen was observed just during the first sampling in building I, L. mono- cytogenes was found in building II at the third sampling event. The salting area in building I had the highest proportion of positive samples with the highest diversity of PFGE types. Moreover, L. monocytogenes PFGE type 3 (sequence type -ST- 204) was first detected in building II in the third visit, and spread through this building until the end of the study. The answers to the questionnaire implied that lack of hygienic barriers in specific parts of the facilities and uncontrolled personnel flow were the critical factors for the spread of L. monocytogenes within and between buildings. Knowledge of the patterns of L. monocytogenes colonization can help a more rational design of new cheesemaking facilities, and improve the food safety within current facilities. 1. Introduction Listeria monocytogenes is a ubiquitous bacterium that can be isolated from a wide variety of environmental sources, including food-proces- sing environments and a large variety of foods where it can grow over a pH range of 4.39–9.40, even at refrigeration temperatures (Gandhi and Chikindas, 2007; Sauders and Wiedmann, 2007; Swaminathan and Gerner-Smidt, 2007). In 2016, 2536 human cases were reported in 28 EU member states, causing by far the highest number of food-borne diseases-related deaths (EFSA, 2017). Food safety regulations in many countries such as the USA, have tended to adopt a zero tolerance policy for L. monocytogenes in ready-to-eat (RTE) food products, as human listeriosis outbreaks have been most often associated with RTE products that are consumed without prior cooking (Painter and Slutsker, 2007; Swaminathan and Gerner-Smidt, 2007). Cheese and other dairy products are within this type of food category. Unlike many other bacterial foodborne pathogens, L. monocytogenes can grow in milk at refrigeration temperatures (Kozak et al., 2018; Thamnopoulos et al., 2018) and reach potentially infectious levels in high-moisture and surface-ripened cheeses (Bernini et al., 2013; Cogan, 2011). The sur- vival and growth of L. monocytogenes in dairy environments depends on the manufacturing, ripening and storage conditions (Almeida et al., 2013; Pintado et al., 2005). Similarly, the strain-to-strain variability of survival in different storage conditions is associated to the different L. monocytogenes genetic lineages (De Jesus and Whiting, 2003; Mataragas et al., 2008). Although L. monocytogenes can decrease in different types of cheeses during ripening and storage (Valero et al., 2014; Wemmenhove et al., 2013), the risk of cross-contamination during processing is still high due to the possible presence of this organism in the dairy environment https://doi.org/10.1016/j.ijfoodmicro.2018.09.003 Received 30 April 2018; Received in revised form 30 August 2018; Accepted 3 September 2018 ⁎ Corresponding author at: Microbiology Division, Department of Biotechnology and Food Science, University of Burgos, Plaza Misael Bañuelos, 09001 Burgos, Spain. E-mail address: drlazaro@ubu.es (D. Rodriguez-Lázaro). International Journal of Food Microbiology 289 (2019) 64–71 Available online 05 September 2018 0168-1605/ © 2018 Elsevier B.V. All rights reserved. T