TABLE 2.

Results of bla_CMY-2 and bla_CTX-M PCR of E. coli isolates from cattle feces in the Pacific Northwest

Time period	Isolate selection or ceftiofur concn in MacConkey medium	Total no. of isolates tested	No. of farms	blaCMY-2 positive		blaCTX-M positive
				No.	% (95% CI)a	No.	% (95% CI)a
2002-2003	Reduced susceptibility to ceftiofur per breakpoint agar test (17)	157	14	137	87.3 (80.8–91.9)	0	0 (0–3.0)
2008	Reduced susceptibility to ceftiofur per breakpoint agar test (17)	41	4	40	97.6 (85.6–99.9)	0	0 (0–10.7)
2008	8 μg/ml ceftiofur	24	4	23	95.8 (76.9–99.8)	0	0 (0–17.2)
2008 total		65	4	63	96.9 (88.4–99.5)	0	0 (0–7.0)
2011	0 μg/ml ceftiofur	45	4	14	31.1 (18.6–46.8)	2	4.4 (0.1–16.4)
2011	2 μg/ml ceftiofur	44	4	24	54.5 (39.0–69.3)	5	11.4 (3.0–20.2)
2011 total		89	4	38	42.7 (32.4–53.6)	7	7.9 (3.5–16.1)
2011	Reduced susceptibility to ceftiofur according to disk diffusion results (inhibition zone size of ≤22 mm) (19, 20)	47	4	37	78.7 (63.9–88.8)	7	14.9 (6.7–28.9)

^aCI, confidence interval (23).