Whole Genome Sequence Analysis of Salmonella Enteritidis PT4 Outbreaks from a National Reference Laboratory’s Viewpoint

Discussion S. Enteritidis remains linked to egg-related outbreaks, albeit in the described outbreaks to non-commercial eggs from privately owned laying hens. In response to two geographically separated outbreaks occurring in the same time period in Belgium, the NRL-FBO received food samples from which Salmonella was isolated and the NRCSS received Salmonella isolates from human cases of these outbreaks. With the traditional epidemiological and microbiological investigations, i.e. phage typing and MLVA, the isolates of both outbreaks were classified as PT4 and variant PT4a, and as profile 3-10-5-4-1. Phage type PT4 and MLVA profile 3-10-5-4-1 are frequently observed for human isolates in Belgium. Therefore, the gold standard subtyping methods might not have been sufficiently discriminative to establish or exclude a common source of contamination for both outbreaks, which now could only be distinguished by their separate geographical location. However, there could still be a common origin, e.g. a common breeding flock of the laying hens bought by the private persons. As WGS has been postulated as a universal subtyping method with ultimate resolution, the two outbreaks were retrospectively examined with WGS. Moreover, they were a good case study to investigate the feasibility of using WGS for outbreak investigation by a National Reference Laboratory, as both human and food isolates were available. An additional aspect that was evaluated in this study concerns the WGS data an...
Source: PLOS Currents Outbreaks - Category: Epidemiology Authors: Source Type: research