Utility of Whole Genome Sequencing To Describe the Persistence and Evolution of Listeria monocytogenes Strains within Crabmeat Processing Environments Linked to Two Outbreaks of Listeriosis

Abstract

This article describes the identification and investigation of two extended outbreaks of listeriosis in which crabmeat was identified as the vehicle of infection. Comparing contemporary and retrospective typing data of Listeria monocytogenes isolates from clinical cases and from food and food processing environments allowed the detection of cases going back several years. This information, combined with the analysis of routinely collected enhanced surveillance data, helped to direct the investigation and identify the vehicle of infection. Retrospective whole genome sequencing (WGS) analysis of isolates provided robust microbiological evidence of links between cases, foods, and the environments in which they were produced and demonstrated that for some cases and foods, identified by fluorescent amplified fragment length polymorphism, the molecular typing method in routine use at the time, were not part of the outbreak. WGS analysis also showed that the strains causing illness had persisted in two food production environments for many years and in one producer had evolved into two strains over a period of around 8 years. This article demonstrates the value of reviewing L. monocytogenes typing data from clinical cases together with that from foods as a means of identifying potential vehicles and sources of infection in outbreaks of listeriosis. It illustrates the importance of reviewing retrospective L. monocytogenes typing alongside enhanced surveillance data to characterize extended outbreaks and inform control measures. Also, this article highlights the advantages of WGS analysis for strain discrimination and clarification of evolutionary relationships that refine outbreak investigations and improve our understanding of L. monocytogenes in the food chain.

The use of next generation sequencing for improving food safety: Translation into practice

“…For example, isolates in a food processing plant may cluster separately from all other isolates in a database but still be 30 SNPs/alleles from each other. This indicates that the isolates share a common ancestor and may have evolved from a resident strain in the premises and potentially persistent (Elson et al, in publication). This can happen when microbial populations experience frequent reduction in numbers (i.e.…”

Interpretation of Whole-Genome Sequencing for Enteric Disease Surveillance and Outbreak Investigation

“…Therefore, “matches” between isolates strongly suggest some relationship, whether separated in time. For example, WGS is making it possible to recognize persistence problems due to contaminated food production or preparation environments (Elson et al , 2019).…”

Human foodborne listeriosis in England and Wales, 1981 to 2015

“…Amongst all eight outbreaks (designated O1–O8), five of these have been previously described [11, 14, 19, 20]. For all the outbreaks, the implicated food types were all ready-to-eat products of animal origin (Table 4).…”

“…In England and Wales, human listeriosis has been investigated since the 1980s and both foodborne outbreaks and single sporadic cases associated with the consumption of a range of foods were identified [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. However, less than half of the foodborne incidents identified have been described in the peer reviewed literature.…”