Table 5.

Changes in carriage of stx1 and consistent detection of stx2 in twelve isolates of O121:H19 from PCR analysis by two labs.

#Isolates Sharing PCR Profile	PCR	Year of PCR	LAB	PCR stx1	Detection 2 stx2	Comments
6	First 1	2013	A	+	+	LAB A PCRs are the same over years, LAB C negative for stx1
	Second	2015	C	-	+
	Third	2017	A	+	+
2	First	2013	A	-	+	All three PCRs are the same never stx1
	Second	2015	C	-	+
	Third	2017	A	-	+
2	First	2013	A	-	-	LAB A and LAB C initially the same, stx1 positive in second LAB A analysis
	Second	2015	C	-	-
	Third	2017	A	+	-
2	First	2013	A	+	+	Second LAB A analysis negative for stx1 and now agrees with LAB C
	Second	2016	C	-	+
	Third	2017	A	-	+

¹ PCR first = initial isolation. ² PCR detection + = positive, - = negative.