ONGOING SALMONELLA ENTERITIDIS OUTBREAK LINKED TO A COMMON EGG DISTRIBUTOR

Salmonella Enteritidis, a major cause of foodborne outbreaks, is associated with invasive infections. It is mainly linked to eggs and thus tightly regulated in the poultry industry in Europe and Israel. S.Enteritidis has emerged as the predominant serotype in Israel since 2015. Furthermore, it was isolated from at least 2,540 patients during May 2017 - April 2018, in comparison to 902 cases in the previous year (2.8-fold increase). During this period S.Enteritidis accounted for 51 percent of salmonellosis cases in Israel which marks a major increase. Salmonellosis investigations were conducted nationwide for case clusters implicating family households, kindergartens, hostels, and restaurants. Epidemiology traceback, and laboratory data have linked several of the outbreak clusters to eggs; several table egg layers farms and egg distributors were identified as possible sources. Pulsed-Field Gel Electrophoresis (PFGE) analysis of isolates from major clusters revealed a common pulsotype. Further analysis by whole genome sequencing (WGS) and whole genome multi locus sequence typing (wgMLST) identified several sub-clones. Of particular interest is the identification of a clone from geographically distinct salmonellosis clusters that were temporally linked with a common egg distributor. Detection of these clones in egg-laying flocks resulted in several recalls of fresh eggs for this distributor (September 2017, October 2017 and February 2018), which led to an initial decrease in morbidity. A previous nationwide outbreak reported during 2015-2016 appears to have been caused by an unrelated genotype indicative of multiple contamination sources. Coordinated laboratory and epidemiological investigations of case clusters, as well as intensified inspection of table egg layers farms and food are ongoing in order to trace and eliminate sources and underpin public health.