156 EUROSURVEILLANCE Vol. 12 · Issues 3–6 · Apr–Jun 2007 · www.eurosurveillance.org Outbreak report J Mossong (Joel.Mossong@lns.etat.lu) 1 , P Marques 2 , C Ragimbeau 1 , P Huberty-Krau 3 , S Losch 4 , G Meyer 4 , G Moris 5 , C Strottner 6 , W Rabsch 7 , F Schneider 1 1. Microbiology Unit, Laboratoire National de Santé (National Health Laboratory, LNS) Luxembourg 2. Centre de Recherche Public – Santé (Research Centre for Health, CRP- Santé), Luxembourg 3. Health Inspection Unit, Direction de la Santé (Health Directorate), Luxembourg 4. Administration des Services Vétérinaires (Veterinary Services Administration), Luxembourg 5. Food Control Unit, Laboratoire National de Santé (National Health Laboratory, LNS), Luxembourg 6. Administration des Services Techniques de l’Agriculture (Technical Services for Agriculture Administration), Luxembourg Salmonella enterica serovar 4,[5],12:i:- phage type DT193 emerged as the dominant serovar in Luxembourg in 2006, elderly and in day-care centers. Strains identical to the outbreak strain were recovered from two control meals, a nappy changing table, retail sausages and caecal porcine samples at an abattoir. Locally produced pork meat is strongly suspected to have been the vehicle for the outbreaks, although the precise mechanisms remain unclear. Salmonella enterica is one of the most common causes of whole, most human cases in Luxembourg have recently been due to serovars S. or S. Salmonella isolates were referred to the National Health Laboratory in Luxembourg. Of those, 66% were S. Enteritidis and 20% were S. Typhimurium. In recent years, the emergence of a Salmonella enterica monophasic serovar 4,[5],12:i:- has been described that was [4], Thailand [5] and Taiwan [6]. The strains are called monophasic by the ‘-’ after the second colon in the antigenic formula 4,[5],12: i:-. Genotypic, biochemical and phenotypic characterisations indicate that such strains usually represent monophasic variants of the serovar S. human cases with this monophasic serovar 4,[5],12:i:- were rare in Luxembourg, with on average two to three cases reported annually. However, Salmonella serovar 4,[5],12:i:- was responsible for the two large outbreaks in 2006 that are described in this report and is now the dominant human serovar in Luxembourg. The microbiology unit of the National Health Laboratory in Luxembourg is the reference laboratory for human salmonellosis and member of the European Enter-net surveillance network [8]. Human Salmonella isolates from all private and hospital laboratories as well as veterinary isolates from food safety, animal feed control and animal pathology laboratories in Luxembourg are characterised by EPIFOOD was initiated between all public institutions involved in food safety in Luxembourg. It systematically conducts enhanced sampling of different levels of the food chain and compares bacterial pathogens in the food chain with human isolates using molecular typing methods. In particular, routine sampling of bovine and porcine caecal contents was started in all three abattoirs in Luxembourg with the aim of isolating Salmonella. On those farms where the routine programme detected Salmonella, additional samples were taken. During the investigation of the 2006 outbreaks, the patients were and food consumption prior to illness. In supermarkets and catering facilities of institutions in which patients were staying, samples were taken from food items that were considered at risk. in the Salmonella reference laboratory during a three-week period Figure 1 Weekly number of human monophasic Salmonella cases in Luxembourg in 2006, based on date of stool sample collection 0 10 20 30 40 1 Jan 06 1 Apr 06 1 Jul 06 1 Oct 06 1 Jan 07 Date Number of cases