Antimicrobial resistance of Salmonella enterica serovar Heidelberg isolated from poultry in Alberta

Figures & data

Table 1.  Annual antimicrobial susceptibilities of S. Heidelberg isolates from poultry obtained by the Food Safety and Animal Health Division of AARD from 1996 to 2010.

		AMX		TET		TIO				GEN				STR		SXT
Year	Number of isolates	No. R	% R	No. R	% R	No. R	% R	No. I	% I	No. R	% R	No. I	% I	No. R	% R	No. R	% R
1996	2	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0
1997	15	3	20.0	1	6.7	0	0.0	0	0.0	5	33.3	0	0.0	3	20.0	0	0.0
1998	61	26	42.6	2	3.3	0	0.0	0	0.0	18	29.5	0	0.0	11	18.0	0	0.0
1999	90	31	34.4	11	12.2	5	5.6	0	0.0	16	17.8	5	5.6	21	23.3	5	5.6
2000	86	28	32.6	18	20.9	8	9.3	0	0.0	7	8.1	2	2.3	25	29.1	5	5.8
2001	100	9	9.0	33	33.0	1	1.0	0	0.0	10	10.0	1	1.0	24	24.0	0	0.0
2002	48	5	10.4	19	39.6	1	2.1	0	0.0	0	0.0	0	0.0	18	37.5	1	2.1
2003	52	2	3.8	3	5.8	0	0.0	0	0.0	1	1.9	1	1.9	1	1.9	0	0.0
2004	62	16	25.8	13	21.0	3	4.8	0	0.0	5	8.1	1	1.6	9	14.5	2	3.2
2005	87	13	14.9	14	16.1	1	1.1	0	0.0	5	5.7	0	0.0	8	9.2	1	1.2
2006	79	16	20.3	21	26.6	4	5.1	0	0.0	1	1.3	0	0.0	16	20.3	0	0.0
2007	74	9	12.2	6	8.1	3	4.1	0	0.0	0	0.0	0	0.0	7	9.4	0	0.0
2008	75	6	8.0	1	1.3	0	0.0	1	1.3	0	0.0	0	0.0	5	6.7	0	0.0
2009	95	24	25.3	0	0.0	10	10.5	0	0.0	0	0.0	0	0.0	12	12.6	0	0.0
2010	25	10	40.0	1	4.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0
Overall	951	198	20.8	143	15.0	36	3.8	1	0.1	68	7.2	10	1.1	160	16.8	14	1.5
No. I, number of intermediate susceptibility; % I, percentage of intermediate susceptibility; No. R, number resistant; % R, percentage resistant.

Table 2.  Descriptive statistics for the sources of S. Heidelberg isolates from poultry.

Variable	Number	Proportion (%)
Commodity type
Broiler chicken	113	11.9
Broiler breeder chicken	395	41.5
Layer chicken^a	392	41.2
Layer breeder chicken^a	2	0.2
Meat turkey	14	1.5
Turkey breeder	12	1.3
Missing commodity type	23	2.5
Isolate source
Environment	401	42.2
Fluff	114	12.0
Litter	279	29.3
Other	157	16.5
^aCombined for analysis.

Figure 1.  Predicted probabilities of AMX resistance from the final logistic regression model of S. Heidelberg isolates from poultry in Alberta.

Table 3.  Odds ratios and 95% confidence intervals for the logistic regression model for AMX resistance in S. Heidelberg isolates from poultry.

Variable	OR (95% confidence interval)	Wald P value	LRT P value
Year	0.94 (0.84 to 1.06)	0.32	<0.01
Year^2	1.08 (1.03 to 1.13)	<0.01
Commodity			<0.01
Layers + layer breeders	Referent	–
Broilers	19.51 (5.48 to 69.41)	<0.01
Broiler breeders	15.23 (4.82 to 48.11)	<0.01
Meat turkeys	115.22 (15.04 to 882.64)	<0.01
Turkey breeders	24.01 (1.95 to 295.21)	0.01
Year*commodity			<0.01
Year*broilers	1.23 (0.88 to 1.73)	0.22
Year*broiler breeders	1.32 (1.15 to 1.53)	<0.01
Year*meat turkeys	0.97 (0.49 to 1.92)	0.92
Year*turkey breeders	Omitted	–
Year^2*broilers	0.96 (0.87 to 1.05)	0.33
Year^2*broiler breeders	1.02 (0.96 to 1.07)	0.56
Year^2*meat turkeys	0.86 (0.72 to 1.03)	0.11
Year^2*turkey breeders	0.77 (0.36 to 1.67)	0.51
LRT, likelihood ratio test. Omitted, left out due to model collinearity.

Table 4.  Odds ratios and 95% confidence intervals for the logistic regression model for TIO resistance in S. Heidelberg isolates from poultry.

Variable	OR (95% confidence interval)	Wald P value	LRT P value
Year			<0.01
1996	Omitted	–
1997	Omitted	–
1998	Omitted	–
1999	4.71 (0.52 to 42.73)	0.17
2000	12.75 (1.52 to 106.70)	0.02
2001	Referent	–
2002	2.06 (0.12 to 35.44)	0.62
2003	Omitted	–
2004	5.27 (0.52 to 53.70)	0.16
2005	0.99 (0.06 to 16.73)	1.00
2006	4.55 (0.47 to 43.83)	0.19
2007	6.74 (0.65 to 70.38)	0.11
2008	Omitted	–
2009	24.84 (2.80 to 220.21)	<0.01
2010	Omitted	–
Commodity (all possible contrasts)			0.02
Broiler vs. layer + layer breeder	3.89 (0.90 to 16.76)	0.07
Broiler breeder vs. layer + layer breeder	2.49 (0.98 to 6.33)	0.06
Meat turkey vs. layer + layer breeder	22.63 (4.27 to 119.77)	<0.01
Turkey breeder vs. layer + layer breeder	4.85 (0.45 to 52.62)	0.19
Broiler breeder vs. broiler	0.64 (0.18 to 2.27)	0.49
Meat turkey vs. broiler	5.81 (0.98 to 34.29)	0.052
Turkey breeder vs. broiler	1.24 (0.12 to 13.10)	0.85
Meat turkey vs. broiler breeder	9.09 (2.02 to 40.90)	<0.01
Turkey breeder vs. broiler breeder	1.95 (0.20 to 18.95)	0.56
Turkey breeder vs. meat turkey	0.21 (0.02 to 2.91)	0.25
LRT, likelihood ratio test. Omitted, left out due to insufficient data (all isolates susceptible).

Table 5.  Odds ratios and 95% confidence intervals for the logistic regression model for GEN resistance in S. Heidelberg isolates from poultry.

Variable	OR (95% confidence interval)	Wald P value	LRT P value
Year (units = 1 year)	0.72 (0.64 to 0.81)	<0.01	<0.01
Commodity (all possible contrasts)			<0.01
Broiler vs. layer + layer breeder	27.33 (3.46 to 215.94)	<0.01
Broiler breeder vs. layer + layer breeder	22.92 (3.10 to 169.29)	<0.01
Meat turkey vs. layer + layer breeder	26.57 (2.15 to 328.64)	0.01
Turkey breeder vs. layer + layer breeder	62.40 (3.52 to 1106.55)	<0.01
Broiler breeder vs. broiler	0.84 (0.41 to 1.70)	0.63
Meat turkey vs. broiler	0.97 (0.18 to 5.22)	0.97
Turkey breeder vs. broiler	2.28 (0.25 to 20.78)	0.46
Meat turkey vs. broiler breeder	1.16 (0.24 to 5.67)	0.86
Turkey breeder vs. broiler breeder	2.72 (0.31 to 23.68)	0.36
Turkey breeder vs. meat turkey	2.35 (0.16 to 33.20)	0.53
LRT, likelihood ratio test.

Figure 2.  Predicted probabilities of TET resistance from the final logistic regression model of S. Heidelberg isolates from poultry in Alberta. All turkey breeder isolates were resistant to TET.

Table 6.  Odds ratios and 95% confidence intervals for the logistic regression model for TET resistance in S. Heidelberg isolates from poultry.

Variable	OR (95% confidence interval)	Wald P value	LRT P value
Year	0.45 (0.22 to 0.90)	0.03	<0.01
Year^2	0.83 (0.71 to 0.98)	0.03
Commodity			<0.01
Layers + layer breeders	Referent	–
Broilers	6.14 (1.89 to 19.90)	<0.01
Broiler breeders	7.47 (2.67 to 20.90)	<0.01
Meat turkeys	115.22 (15.04 to 882.64)	<0.01
Turkey breeders	Omitted	–
Year*commodity			<0.01
Year*broilers	1.16 (0.96 to 1.40)	0.14
Year*broiler breeders	1.12 (0.95 to 1.33)	0.18
Year*meat turkeys	1.34 (0.96 to 1.87)	0.09
Year*turkey breeders	Omitted	–
Year^2*broilers	2.37 (1.09 to 5.14)	0.03
Year^2*broiler breeders	1.84 (0.90 to 3.77)	0.09
Year^2*meat turkeys	6.17 (1.24 to 30.74)	0.03
Year^2*turkey	Omitted	–
LRT, likelihood ratio test. Omitted, left out due to insufficient data (all isolates resistant).