TABLE 1.

XbaI-PFGE profiles of wild-type STEC O157:H7 and isolates derived through repeated in vitro passages for a 25-week period at intervals of 3 to 4 days

Strain and PFGE profile	No. of fragment differences from original pattern	No. of colonies showing identity to PFGE profile following no. of subcultures:
		Presubculture	1	10	20	30	40	50
RIMD0509952 (Sakai strain)
I-a	0a	9	14	14	13	13	14	14
I-b	2	5	0	0	0	1	0	0
I-c	1	0	0	0	1	0	0	0
EC1015
II-a	0a	6b	13	7	0	0	0	0
II-b	2	5c	1	0	0	0	0	0
II-c	1	3	0	0	0	0	0	0
II-d	1	0	0	6	14	14	12	0
II-e	3	0	0	1	0	0	0	0
II-f	8	0	0	0	0	0	2	6
II-g	6	0	0	0	0	0	0	8
83-1386
III-a	0a	10	14	12	14	14	14	14
III-b	2	2	0	0	0	0	0	0
III-c	3	1	0	0	0	0	0	0
III-d	3	1	0	1	0	0	0	0
III-e	2	0	0	1	0	0	0	0

^aOriginal pattern.

^bOne of the 6 strains did not contain the stx2 gene.

^cOne of the 5 strains did not contain the stx2 gene.