Table 1. Proportion of fecal samples positive for presumptive STEC.

Method1	Source	Number of positive samples/Number of fecal samples tested per sampling site2
		Site A	Site B	Site C	Site D	Site E	Total
Direct plating	Cattle	0/12	1/12	0/12	1/12	0/12	2/60
	Chicken	0/12	0/12	NA3	NA	NA	0/24
	Sheep	0/12	NA	2/12	NA	2/12	4/36
	Total	0/36	1/24	2/24	1/12	2/24	6/120
IMS	Cattle	0/12	0/12	4/12	3/12	2/12	9/60
	Chicken	0/12	1/12	NA	NA	NA	1/24
	Sheep	2/12	NA	5/12	NA	2/12	9/36
	Total	2/36	1/24	9/24	3/12	4/24	19/120

¹Enrichment broths were subjected to direct plating from July to December 2008 or to immunomagnetic separation (IMS) from January to June 2009.

²Sampling sites correspond to regions in the Culiacan Valley, Sinaloa, Mexico, as shown in Figure 1.

³NA, None available.