Evaluation of whole-genome sequencing for outbreak detection of Verotoxigenic Escherichia coli O157:H7 from the Canadian perspective

Table 2 Features of Eight Outbreaks of Verotoxigenic Escherichia coli O157:H7 Characterized by Whole Genome Sequencing in Canada

						Number of Genetic Differences Among Outbreak-Related Isolates
Outbreak	Year	Number of Lab Confirmed Cases	Suspect / Confirmed Source	Number of Implicated PFGE Patterns / MLVA Profiles^d	Number of Isolates Sequenced in the Study	SNVs	wgMLST alleles
1	2011	14	Raw shelled walnuts	1 / 2	14	0–3	0–4
2	2011	2	In-shell hazelnuts	1 / 2	2	0	4
3^a	2012	15	Preformed beef patties	6 / 8	42^b	Group 1^c: 0–1 Group 2^c: 0–1 Group 3^d: 0 Group 4: 0–3 Group 5^c: 0–1 Group 6^d: 0 All Isolates: 0–110	Group 1^c: 1–5 Group 2^c: 0–3 Group 3^d: 1–4 Group 4: 0–9 Group 5^c: 1–3 Group 6^d: 2–4 All Isolates: 0- > 100
4	2012	23	Romaine lettuce	2 / 1	23	0–1	0–7
5	2012	18	Beef products	1 / 1	25^b	0–3	0–4
6^a	2012	9	Frozen beef burgers	7 / 8	36^b	Group 1^d: 0–2 Group 2^d: 0 Group 3^d: 0–1 All Isolates: 0–106	Group 1^d: 0–4 Group 2^d: 0–3 Group 3^d: 0–2 All Isolates: 0- > 90
7	2012	31	Fast Food lettuce	3 / 1	31	0–2	0–8
8	2013	28	Raw milk cheese	4 / 4	44^b	0–5	0–9

PFGE pulsed-field gel electrophoresis, MLVA multilocus variable-number tandem-repeat analysis, SNVs single nucleotide variants, wgMLST whole-genome multilocus sequence typing
^aSuspected multi-strain event; isolates split into multiple groupings and one or more potential outliers
^bOne or more food isolates were sequenced
^cOnly includes food isolates
^dContains clinical and food isolates

ISSN: 1471-2164