Pulsed-Field Gel Electrophoresis characterization of Listeria monocytogenes isolates from cheese manufacturing plants in São Paulo, Brazil

Abstract

This study aimed to evaluate the occurrence of Listeria monocytogenes in cheese and in the environment of three small-scale dairy plants (A, B, C) located in the Northern region state of São Paulo, Brazil, and to characterize the isolates using conventional serotyping and PFGE. A total of 393 samples were collected and analyzed from October 2008 to September 2009. From these, 136 came from dairy plant A, where only L. seeligeri was isolated. In dairy plant B, 136 samples were analyzed, and L. innocua, L. seeligeri and L. welshimeri were isolated together with L. monocytogenes. In dairy plant C, 121 samples were analyzed, and L. monocytogenes and L. innocua were isolated. Cheese from dairy plants B and C were contaminated with Listeria spp, with L. innocua being found in Minas frescal cheese from both dairy plants, and L. innocua and L. monocytogenes in Prato cheese from dairy plant C. A total of 85 L. monocytogenes isolates were classified in 3 serotypes: 1/2b, 1/2c, and 4b, with predominance of serotype 4b in both dairy plants. The 85 isolates found in the dairy plants were characterized by genomic macrorestriction using ApaI and AscI with Pulsed Field Gel Electrophoresis (PFGE). Macrorestriction yielded 30 different pulsotypes. The presence of indistinguishable profiles repeatedly isolated during a 12-month period indicated the persistence of L. monocytogenes in dairy plants B and C, which were more than 100 km away from each other. Brine used in dairy plant C contained more than one L. monocytogenes lineage. The routes of contamination were identified in plants B and C, and highlighted the importance of using molecular techniques and serotyping to track L. monocytogenes sources of contamination, distribution, and routes of contamination in dairy plants, and to develop improved control strategies for L. monocytogenes in dairy plants and dairy products.

Characterization of epidemic clones of Listeria monocytogenes serotype 4b isolated from humans and meat products in Brazil

“…Similar results were observed in a posterior study with human clinical specimens [18]. Recent studies also described the high occurence of 4b serotype in dairy products [17,30], ready-to-eat vegetables [31] and meat products retailed [6] in Brazil. Although the wide distribution of serotype 4b has been described in Brazil, details about the occurrence of ECs and your association with sporadic cases or outbreaks is ignored.…”

Training of Food Handlers in a Hotel: Tool for Promotion of the Food Safety

“…Recent studies reported they are sources of contamination in cheeseprocessing plant environment (Dias et al 2012;Barracelli et al 2014) and small-sized yogurt plant (Cusato et al 2013) as well as restaurants (Ajala et al 2010). In fact, all samples have been purposefully manipulated under inadequate sanitary conditions; consequently, high counts of mesophilic aerobes and coliform bacteria at 35 and 45C were found, with values above 6 log cfu/g and 10 2 MPN/g, respectively.…”

Prevalence and characterization of Staphylococcus aureus isolated from goat milk powder processing plants

“…Previous studies on foodborne pathogens in dairy processing focused on Listeria monocytogenes and Escherichia coli O157:H7 (Almeida et al, 2013;Barancelli et al, 2014;Cagri-Mehmetoglu et al, 2011). However, reports on S. aureus in goat milk powder processing plants are relatively scanty.…”