Multi-country outbreak of S. Enteritidis, MLVA type 2-9-7-3-2 and 2-9-6-3-2 infections

First published in EFSA Supporting Publications
28 October 2016
27 October 2016
Technical Report
A multi-country outbreak of Salmonella Enteritidis phage type (PT) 8 with multiple locus variablenumber tandem repeat analysis (MLVA) profiles 2-9-7-3-2 and 2-9-6-3-2, linked to eggs, is ongoing in the EU/EEA. Based on Whole Genome Sequencing (WGS), isolates are part of two distinct but related genetic clusters. ECDC and EFSA are liaising with relevant authorities in the Member States and at the EU level to facilitate the coordination of investigation and response measures. From 1 May 2016 to 12 October 2016, seven EU/EEA countries have reported 112 confirmed cases belonging to two distinct WGS clusters, and 148 probable cases sharing the S. Enteritidis MLVA profiles 2-9-7-3-2 or 2-9-6-3-2. Outbreak cases, both confirmed and probable, have been reported by Belgium, Denmark, Luxembourg, the Netherlands, Norway, Sweden and the United Kingdom. Nine of the confirmed cases are associated with a travel history to Hungary or Poland, both of which countries are also considered to be affected by this outbreak. In addition, Croatia reported a cluster of S. Enteritidis cases, including a fatal case, with an epidemiological link to the outbreak. The characterisation of the Croatian isolates is currently ongoing. The food safety authorities in Belgium, Croatia, the Netherlands and Scotland have carried out extensive environmental and food investigations to identify the source of this outbreak. Since S. Enteritidis is mostly associated with chickens, the investigations focused, among other food items, on the tracing of eggs and chicken meat supply chains into food establishments where outbreak cases had reported eating. As of 25 October 2016, these investigations showed that a number of food establishments and at least a retail chain in Croatia received eggs supplies from packing centre B in Poland. Additionally, the cases in the Croatian cluster had consumed eggs originating from packing centre B in Poland. Additional sampling of eggs intended for direct human consumption originating from the implicated Polish packing centre B was performed in the Netherlands in October 2016 yielding positive results for S. Enteritidis contamination. Eight nonhuman S. Enteritidis isolates from the abovementioned eggs were found to have MLVA type 2-9-7-3-2 and to belong to the two WGS clusters associated with this outbreak. S. Enteritidis isolates from food testing in Norway, sampled in May and November 2015 and identified through a company’s own check controls, were also demonstrated to be part of one of the WGS clusters defining the outbreak. The isolates originated from unpasteurised (before processing) liquid eggs, which were made from fresh eggs imported to Norway from the Polish packing centre B. The available evidence from WGS, food and environmental investigations, as well as from tracing-back investigation of eggs, establishes a link between this multi-country foodborne outbreak and the packing centre B in Poland, pointing at eggs as the most likely vehicle of infection for at least part of the outbreak cases. Additional information from epidemiological, food and WGS investigations might bring further evidence on the possible vehicles and sources of infection associated with this outbreak. The molecular typing of isolates deriving from other countries, not yet confirmed to be affected by this outbreak, could help in understanding the actual geographical distribution of the outbreak. Competent authorities in Poland and in the Member States where eggs from the packing centre B were distributed, have already introduced restrictive measures to withdraw and stop placing implicated eggs on the market and investigations are ongoing to eliminate the source. Due to the large outbreak that is currently ongoing, national authorities, particularly in affected countries, could also consider reminding food establishments and food providers of good practices for safely preparing and handling food at risk of Salmonella contamination. In order to monitor the circulation of the outbreak strains and keep track of the number of affected countries, all EU/EEA countries should consider enhancing their surveillance for S. Enteritidis infections acquired within the EU/EEA. It would be of particular value to perform MLVA typing and/or WGS. To support the investigations in countries, ECDC and the European reference laboratory for Salmonella continue offering WGS services for isolates suspected to be linked to the outbreak, particularly if the isolates originate from countries not yet confirmed to be affected by this outbreak. New cases and critical developments should be reported to EPIS-FWD (Epidemic Intelligence Information System for Food- and Waterborne Diseases and Zoonoses). The competent authorities in the food safety and the public health sectors in affected Member States and at the European level are encouraged to continue sharing information on the epidemiological, microbiological and environmental investigations, including issuing relevant notifications using the Rapid Alert System for Food and Feed (RASFF) and the Early Warning and Response System (EWRS), the latter representing the official channel to notify cross-border threats. 
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