Table 4. Mann-Kendall and Sen estimates for trend statistics of antimicrobial drug resistance among Escherichia coli isolates of human and animal origin, United States, 1950–2002.

Drug	Source	Years of time series	No.*	Mann-Kendall trend test Z value	Sen’s slope estimate
					p value	Q† (95% CI)
Ampicillin	Human	1950–2001	52	4.91	<0.001	0.59 (0.38–0.81)
	Animal	1962–2002	37	3.95	<0.001	0.97 (0.60–1.33)
Cephalothrin	Human	1950–2001	52	−2.38	<0.05	−0.20 (−0.34 to 0)
	Animal	1962–2002	37	2.52	<0.05	0.43 (0.08–0.77)
Sulfonamide	Human	1950–2001	52	3.41	<0.001	0.49 (0.23–0.73)
	Animal	1962–2002	37	3.24	<0.01	1.11 (0.34–1.85)
Streptomycin	Human	1950–2001	52	1.16	>0.1	0.15 (−0.10 to 0.39)
	Animal	1962–2002	37	2.24	<0.05	0.90 (0.14–1.41)
Tetracycline	Human	1950–2001	52	3.84	<0.001	0.45 (0.22–0.70)
	Animal	1962–2002	37	2.78	<0.01	0.70 (0.21–1.21)
Trimethoprim/sulfamethoxazole	Animal	1982–2002	21	2.64	<0.01	1.17 (0.32–2.15)
Chloramphenicol	Animal	1962–2002	37	2.75	<0.01	0.30 (0–0.59)
Cefoxitin	Animal	1982–2002	21	3.72	<0.001	0.88 (0.28–1.38)
Gentamicin	Animal	1978–2002	25	4.53	<0.001	1.28 (0.90–1.69)
Amoxicillin/clavulanic acid	Animal	1962–2002	37	3.09	<0.01	0.14 (0–0.38)
Kanamycin	Animal	1962–2002	7	4.38	<0.001	1.11 (0.59–1.50)

*Number of annual values for calculation of trend analysis.
†Magnitude of annual percentage increase or decrease.