ARCHIVED - UPDATE - Salmonella Heidelberg Ceftiofur-Related Resistance in Human and Retail Chicken Isolates - 2006 to 2008

The purpose of this web-report is to update our "Salmonella Heidelberg – Ceftiofur-Related Resistance in Human and Retail Chicken Isolates" posted in 2007 (http://www.phac-aspc.gc.ca/cipars-picra/heidelberg/heidelberg-eng.php). The following is a simple description of the data, based on the CIPARS 2006 Annual Report, together with additional data up to and including 2008. Please refer to Section III – Integrated Surveillance of this 2006 Annual Report for an in-depth description of these surveillance findings, limitations to the data, as well as CIPARS activities in this area.

Provincial trends

After 2006, in Québec we saw a statistically significant increase in ceftiofur resistance among retail chicken Escherichia coli, and an apparent re-emergence of ceftiofur resistance in isolates from retail chicken S. Heidelberg, with a similar (though delayed) trend occurring in human cases of S. Heidelberg (Figure 1, Table 1). In Ontario, increases in the proportion of ceftiofur-resistant chicken isolates had already started in early 2006. Since the last quarter of 2006, the prevalence of ceftiofur resistance in retail chicken from Ontario remained steady in E. coli, though the prevalence of ceftiofur-resistant isolates fluctuated in chicken S. Heidelberg, and ceftiofur resistance re-emerged after the second quarter of 2007 in human cases of S. Heidelberg.

Since 2005, CIPARS identified only one ceftiofur-resistant isolate out of 37 S. Heidelberg collected from retail chicken from Saskatchewan. In British Columbia, 56% of the nine S. Heidelberg detected in chicken through pilot retail surveillance conducted in 2005, 2007, and 2008¹ were resistant to ceftiofur (Table 1).

Between 2007 and 2008, ceftiofur resistance in retail chicken E. coli went from 29% (12/42) to 46% (29/63) in British Columbia, 22% (35/157) to 26% (31/121) in Ontario, 13% (17/128) to 18% (20/110) in Québec, and 13% (10/75) to 18% (14/76) in Saskatchewan (Table 1).

The decreasing prevalence of S. Heidelberg in both retail chicken and humans highlighted in the previous S. Heidelberg report was confirmed after 2006 in the provinces of Ontario and Québec. This decrease appears to be independent of the susceptibility profile.

Figure 1: Proportion (moving average of previous three quarters) of isolates resistant to ceftiofur among retail chicken E. coli, and retail chicken and human clinical S. Heidelberg isolates from 2003 to 2008 (preliminary) in Québec and Ontario.*

* The yearly averages of the quarterly values presented in Figure 1 do not necessarily match annual proportions presented in Table 1, because in Figure 1 each of these data points represents the average of the previous three quarters.

Table 1. Annual proportion of human and retail chicken S. Heidelberg isolates and chicken E. coli isolates resistant to ceftiofur.

¹ In this document, 2008 data are preliminary.