A severe gastroenteritis outbreak of Salmonella enterica serovar Enteritidis PT8, with PFGE profile XbaI.0024 and MLVA profile 2-9-7-3-2 following a christening reception, Greece, 2016

In June 2016, a Salmonella enterica serovar Enteritidis outbreak (n = 56) occurred after a christening reception in Central Greece, mainly affecting previously healthy adults; one related death caused media attention. Patients suffered from profuse diarrhoea, fever and frequent vomiting episodes requiring prolonged hospitalisation and sick leave from work, with a 54% hospital admission rate. The majority of cases experienced serious illness within <12 h of attending the party. We investigated the outbreak to identify the source(s) of infection and contributing factors to the disease severity. From the retrospective cohort study, the cheesy penne pasta was the most likely vehicle of infection (relative risk 7·8; 95% confidence interval 3·6-16·8), explaining 79% of the cases. S. enterica ser. Enteritidis isolates were typed as phage-type PT8, pulsed-field gel electrophoresis type XbaI.0024, multiple locus variable-number tandem repeat analysis-type 2-9-7-3-2. The strain did not share the single-nucleotide polymorphism address of the concurrent European S. enterica ser. Enteritidis PT8 outbreak clusters. Following five consecutive years with no documented S. enterica ser. Enteritidis outbreaks in Greece, this outbreak, likely associated with a virulent strain, prompted actions towards the enhancement of the national Salmonella molecular surveillance and control programmes including the intensification of training of food handlers for preventing similar outbreaks in the future. Advanced molecular techniques were useful in distinguishing unrelated outbreak strains.