WGS Cluster Assessment Tool

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Considerations for assessing Salmonella, E. coli and Shigella clusters for further follow-up

New or updated multi-jurisdictional1 Salmonella, E.coli or Shigella cluster considered genetically related by WGS2

Assessment and Review

Prioritization based on the following considerations, as relevant:

                          • Serotype frequency
                          • Number of cases in the cluster
                          • Allele range and branching
                          • Demographic profiles
                          • Isolation date ranges (or available dates)
                          • Presence of a nonclinical isolate in the cluster 
                          • NML’s prioritization level
                          • Historical context (what we have previously learned about the cluster)
                          • How the isolates in the cluster relate to each other & all other isolates in PNC database
                          • Other unique or potentially interesting features

Potential follow-up with P/Ts for available exposure information, taking into account purpose of follow-up and number of requests to P/Ts

Further investigation, if warranted based on review of available information

Note: these are intended to be guidelines; if additional information on clusters is available and suggests that further follow-up on clusters not meeting these criteria is warranted, CFEZID may initiate follow-up.

1 Clusters are considered multi-jurisdictional when they contain human isolates from 2 or more P/Ts

2 Guidelines for WGS interpretation are determined by the Public Health Agency of Canada’s National Microbiology Laboratory