Genetic diversity and antimicrobial resistance among isolates of Escherichia coliO157: H7 from feces and hides of super-shedders and low-shedding pen-mates in two commercial beef feedlots

Table 1 Pens of cattle sampled in Alberta Canada in 2007 with 1 fecal grab sample and 1 hide swab collected per steer at each sampling and PFGE performed on samples positive for E. coli O157:H7

Feedlot	A							B				Total
Pen	1	2	3	4	5	6	7	1	2	3	4
cattle (n)	153	152	153	253	258	155	233	151	235	138	106	1987
Sample 1 date	May 22	Jun 4	Jul 20	Jul 27	Sep 26	Oct 9	Oct 23	Jul 6	Jul 12	Aug 10	Aug 30
SS fecal isolates (n)	2	36	12	19	7	3	0	19^x	44	10	1	153
SS perineal swabs (n)	2	30	11	17	3	3	0	17	40	7	1	131
LS fecal isolates (n)	13	37	100	54	24	2	1	36	107	20	31	425
Sample 2 date	Sep 24	Sep 6	Oct 3	Oct 17	Dec 10	Nov 29	Dec 6	Sep 28	Sep 28	Nov 14	Nov 27
SS fecal isolates (n)	1	0	0	0	0	0	0	8^x	0	0	0	9
SS perineal swabs (n)	0	0	0	0	0	0	0	6	0	0	0	6
LS fecal isolates (n)	3	10	0	2	3	0	1	40	9	3	0	71
LS fecal isolates from former SS (n)	0	1	0	2	2	0	0	7	9	0	0	21
Total isolates tested by PFGE (n)	21	113	123	92	37	8	2	126	200	40	33	795
Total REPC (n)	1	12	14	14	6	1	1	20	13	6	6	85^y
Total unique isolates (n)	8	33	11	14	12	6	0	13	17	8	11	86^y
SS fecal & SS perineal swab in same REPC (n)	1	1	0	0	0	0	NA^z	0	0	0	0	2

Numbers of super–shedders (SS)^v and low- shedders (LS)^w within pens. Numbers of, restriction endonuclease digestion clusters (REPC, 90% or greater similarity) and unique isolates (< 90% similarity) within and across pens.
^vSuper-shedder, shedding at least 10⁴ CFU E. coli O157:H7/g feces.
^wLow-shedder, shedding < 10⁴ CFU E. coli O157:H7/g feces.
^xOne steer was a super-shedder at both samplings.
^yTotal comparing all isolates across pens.
^zNA, not applicable, no super-shedders in pen.

ISSN: 1746-6148