Table 4.

Multivariable Cox proportional hazard regression model of susceptibility of Escherichia coli isolates from non-urinary origin to different antimicrobials in this study, in canine clinical infections at the Cornell University Animal Health Diagnostic Center (AHDC), 2007–2020.

	Hazard ratio	Probability of lower MIC¶	P-value	adj. P-value§	95% CI
Ticarcillin! (N = 1965 isolates)
Intestinal a
Invasive	1.40	0.58	0.004	0.011	1.11–1.76
Unspecified site	1.15		0.329	0.469	0.87–1.51
Reproductive system	1.83	0.65	< 0.001	< 0.001	1.49–2.24
Skin and soft tissues	1.32	0.57	0.007	0.016	1.08–1.62
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.28	0.56	< 0.001	0.001	1.13–1.45
Isolation date (2015–2017)	1.12		0.130	0.219	0.97–1.31
Ticarcillin-clavulanate! (N = 1830 isolates)
Intestinal a
Invasive	1.13		0.222	0.327	0.93–1.37
Unspecified site	1.06		0.601	0.747	0.85–1.32
Reproductive system	1.46	0.59	< 0.001	< 0.001	1.24–1.72
Skin and soft tissues	1.10		0.250	0.362	0.93–1.30
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.19	0.54	0.005	0.013	1.05–1.33
Isolation date (2015–2017)	1.01		0.903	0.947	0.88–1.15
Cefazolin (N = 2981 isolates)
Intestinal a
Invasive	1.28	0.56	0.004	0.011	1.08–1.51
Unspecified site	1.14		0.192	0.288	0.94–1.39
Reproductive system	1.80	0.64	< 0.001	< 0.001	1.60–2.03
Skin and soft tissues	1.29	0.56	< 0.001	< 0.001	1.14–1.46
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.27	0.56	< 0.001	0.001	1.12–1.45
Isolation date (2015–2017)	0.94		0.390	0.539	0.82–1.08
Isolation date (2018–2020)	0.77	0.44	< 0.001	< 0.001	0.68–0.87
Cephalothin! (N = 1534 isolates)
Intestinal a
Invasive	1.20		0.143	0.235	0.94–1.52
Unspecified site	0.90		0.509	0.681	0.65–1.24
Reproductive system	1.44	0.59	< 0.001	0.002	1.18–1.77
Skin and soft tissues	1.04		0.739	0.857	0.83–1.29
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.29	0.56	0.002	0.006	1.10–1.50
Isolation date (2015–2017)	1.02		0.780	0.881	0.87–1.21
Cefoxitin! (N = 1831 isolates)
Intestinal a
Invasive	1.01		0.938	0.961	0.82–1.25
Unspecified site	0.96		0.728	0.856	0.76–1.22
Reproductive system	1.27	0.56	0.006	0.015	1.07–1.50
Skin and soft tissues	0.93		0.406	0.551	0.78–1.11
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.10		0.148	0.239	0.97–1.24
Isolation date (2015–2017)	0.79	0.44	< 0.001	0.003	0.69–0.91
Cefovecin (N = 2600 isolates)
Intestinal a
Invasive	1.30	0.57	0.004	0.011	1.09–1.56
Unspecified site	1.15		0.187	0.288	0.94–1.41
Reproductive system	1.51	0.60	< 0.001	< 0.001	1.33–1.73
Skin and soft tissues	1.20	0.55	0.009	0.020	1.05–1.38
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.05		0.538	0.703	0.89–1.25
Isolation date (2015–2017)	0.82		0.028	0.057	0.69–0.98
Isolation date (2018–2020)	0.75	0.43	0.001	0.004	0.63–0.89
Cefpodoxime (N = 2983 isolates)
Intestinal a
Invasive	1.20		0.033	0.063	1.01–1.43
Unspecified site	1.15		0.173	0.274	0.94–1.41
Reproductive system	1.79	0.64	< 0.001	< 0.001	1.56–2.06
Skin and soft tissues	1.23	0.55	0.002	0.007	1.08–1.40
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.12		0.101	0.176	0.98–1.27
Isolation date (2015–2017)	0.89		0.089	0.158	0.77–1.02
Isolation date (2018–2020)	0.83	0.45	0.004	0.011	0.73–0.94
Imipenem (N = 2984 isolates)
Intestinal a
Invasive	1.19		0.794	0.886	0.32–4.45
Unspecified site	1.03		0.964	0.964	0.24–4.49
Reproductive system	4.04	0.80	< 0.001	< 0.001	2.48–6.58
Skin and soft tissues	1.06		0.776	0.881	0.70–1.61
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.04		0.950	0.961	0.32–3.36
Isolation date (2015–2017)	0.79		0.600	0.747	0.33–1.90
Isolation date (2018–2020)	1.08		0.886	0.947	0.36–3.26
Gentamicin (N = 3018 isolates)
Intestinal a
Invasive	1.18		0.031	0.061	1.02–1.38
Unspecified site	1.26		0.032	0.062	1.02–1.55
Reproductive system	1.74	0.64	< 0.001	< 0.001	1.54–1.96
Skin and soft tissues	1.32	0.57	< 0.001	< 0.001	1.17–1.49
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.18	0.54	0.017	0.036	1.03–1.35
Isolation date (2015–2017)	1.20	0.55	0.008	0.019	1.05–1.36
Isolation date (2018–2020)	1.30	0.57	< 0.001	< 0.001	1.14–1.48
Amikacin (N = 3015 isolates)
Intestinal a
Invasive	0.99		0.944	0.961	0.80–1.22
Unspecified site	0.96		0.804	0.886	0.67–1.37
Reproductive system	1.05		0.541	0.703	0.90–1.23
Skin and soft tissues	0.93		0.344	0.483	0.80–1.08
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.15		0.084	0.153	0.98–1.35
Isolation date (2015–2017)	1.04		0.648	0.794	0.89–1.22
Isolation date (2018–2020)	1.13		0.131	0.219	0.96–1.33
Doxycycline (N = 2615 isolates)
Intestinal a
Invasive	1.33	0.57	0.001	0.003	1.12–1.58
Unspecified site	1.34	0.57	0.004	0.012	1.10–1.65
Reproductive system	1.90	0.66	< 0.001	< 0.001	1.67–2.18
Skin and soft tissues	1.40	0.58	< 0.001	< 0.001	1.22–1.61
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.02		0.819	0.891	0.85–1.23
Isolation date (2015–2017)	0.88		0.190	0.288	0.73–1.06
Isolation date (2018–2020)	0.10		0.685	0.828	0.81–1.15
Chloramphenicol (N = 3013 isolates)
Intestinal a
Invasive	1.54	0.61	< 0.001	< 0.001	1.31–1.81
Unspecified site	1.32	0.57	0.006	0.015	1.08–1.61
Reproductive system	1.49	0.60	< 0.001	< 0.001	1.32–1.68
Skin and soft tissues	1.45	0.59	< 0.001	< 0.001	1.28–1.65
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.02		0.720	0.856	0.90–1.16
Isolation date (2015–2017)	0.86	0.46	0.011	0.023	0.76–0.97
Isolation date (2018–2020)	0.90		0.074	0.136	0.80–1.01
Marbofloxacin (N = 2983 isolates)
Intestinal a
Invasive	1.50	0.60	< 0.001	< 0.001	1.27–1.76
Unspecified site	1.64	0.62	< 0.001	< 0.001	1.34–2.00
Reproductive system	2.38	0.70	< 0.001	< 0.001	2.09–2.72
Skin and soft tissues	1.47	0.60	< 0.001	< 0.001	1.28–1.68
Isolation date (2007–2010) a
Isolation date (2011–2014)	1.17	0.54	0.019	0.039	1.03–1.34
Isolation date (2015–2017)	0.96		0.554	0.709	0.84–1.10
Isolation date (2018–2020)	0.99		0.903	0.947	0.88–1.13

^aReference group

^¶Probability = HR/(1 + HR) − calculated if P-value< 0.05 (e.g., a hazard ratio of 2 corresponds to a 0.67 chance of an isolate at this condition to have a lower MIC value compared to an isolate in the reference group)

^!Not tested from 2018 to 2020.

^§P-values were adjusted according to (Benjamini and Hochberg, 1995).