Factors associated with Salmonella prevalence on pork carcasses in very small abattoirs in Wisconsin.

Abstract

The U.S. Department of Agriculture has expressed concern over Salmonella prevalence on pork carcasses. Our objectives were to survey the prevalence of Salmonella on pork carcasses in very small Wisconsin abattoirs, and identify processing conditions and indicator bacteria levels associated with reduced Salmonella prevalence. During April to July 2007, sponge samples were obtained from 181 pork carcasses at 10 Wisconsin abattoirs before carcass washing (carcass half A), and after washing and chilling and before fabrication (carcass half B). Each sample was categorized by whether the carcass was skinned, by wash-water temperature (7 to 43 degrees C), and the duration (1 or 2 days), temperature, and percent relative humidity of chilling. Sponge samples were analyzed qualitatively for Salmonella and quantitatively for Escherichia coli, coliforms, Enterobacteriaceae, and aerobic plate count (APC). Salmonella prevalences on skinned and unskinned prewash carcasses were 11.7 and 8.3%, respectively. Corresponding values for chilled carcasses were 32.0 and 19.5% for 1-day chilled carcasses, and 11.4 and 14.7% for 2-day chilled carcasses. Lower Salmonella prevalence on prewash carcasses was significantly related to lower prewash carcass APC levels (odds ratio = 7.8 per change of 1.0 log CFU/cm2), while lower Salmonella prevalence on chilled carcasses was significantly related to 2-day chilling (odds ratio = 5.2), and chilled-carcass levels of coliforms, Enterobacteriaceae, and APC (odds ratio = 1.5 to 1.9 per change of 1.0 log CFU/cm2). Salmonella prevalence on chilled pork carcasses in very small Wisconsin plants could be reduced by chilling carcasses 2 days before fabrication and improving carcass-handling hygiene.