Prevalence, Enumeration, Serotypes, and Antimicrobial Resistance Phenotypes of Salmonella enterica Isolates from Carcasses at Two Large United States Pork Processing Plants

Abstract

The objective of this study was to characterize Salmonella enterica contamination on carcasses in two large U.S. commercial pork processing plants. The carcasses were sampled at three points, before scalding (prescald), after dehairing/polishing but before evisceration (preevisceration), and after chilling (chilled final). The overall prevalences of Salmonella on carcasses at these three sampling points, prescald, preevisceration, and after chilling, were 91.2%, 19.1%, and 3.7%, respectively. At one of the two plants, the prevalence of Salmonella was significantly higher (P < 0.01) for each of the carcass sampling points. The prevalences of carcasses with enumerable Salmonella at prescald, preevisceration, and after chilling were 37.7%, 4.8%, and 0.6%, respectively. A total of 294 prescald carcasses had Salmonella loads of >1.9 log CFU/100 cm 2 , but these carcasses were not equally distributed between the two plants, as 234 occurred at the plant with higher Salmonella prevalences. Forty-one serotypes were identified on prescald carcasses with Salmonella enterica serotypes Derby, Typhimurium, and Anatum predominating. S. enterica serotypes Typhimurium and London were the most common of the 24 serotypes isolated from preevisceration carcasses. The Salmonella serotypes Johannesburg and Typhimurium were the most frequently isolated serotypes of the 9 serotypes identified from chilled final carcasses. Antimicrobial susceptibility was determined for selected isolates from each carcass sampling point. Multiple drug resistance (MDR), defined as resistance to three or more classes of antimicrobial agents, was identified for 71.2%, 47.8%, and 77.5% of the tested isolates from prescald, preevisceration, and chilled final carcasses, respectively. The results of this study indicate that the interventions used by pork processing plants greatly reduce the prevalence of Salmonella on carcasses, but MDR Salmonella was isolated from 3.2% of the final carcasses sampled.

Prevalencia de Salmonella spp., en ganglios mesentéricos de porcinos en plantas de beneficio Colombianas

“…The present study found S. London and S. Haifa serotypes, which are rather infrequent serotypes in pigs (25). A study performed in Uganda reported S. Newport, S. Guildford, S. Coleypark, S. Damman as frequent pig serotypes (26), previously described in humans.…”

Pathogens of Interest to the Pork Industry: A Review of Research on Interventions to Assure Food Safety

“…However, scalding and singeing are known to decrease the prevalence of Salmonella on carcasses (Dickson and others ). Preevisceration carcasses were 19.1% positive with only 5% of samples containing enumerable levels of Salmonella which is greatly reduced compared to prescalded carcasses (Schmidt and others ). In addition to feces, various lymph nodes have also been documented as being a reservoir for Salmonella (Fosse and others ).…”

“…Overall, the slaughter process decreases the prevalence of Salmonella on the carcass (Saide‐Albornoz and others ; Dickson and others ). After final rinse and carcass chilling, prevalence of Salmonella was found to be 3.7% (Schmidt and others ).…”

“…Commercial pork slaughter follows the general processing steps of stunning and exsanguination, scalding, dehairing and singeing, head removal, evisceration, and final wash. Because Salmonella are carried primarily in the intestinal tract of swine, contaminated fecal material initially on the carcass or released during the slaughter process are risks for Salmonella contamination. In a USDA study of 2 U.S. commercial slaughter facilities, 91% of prescald carcasses were positive for Salmonella (Schmidt and others ). Not only were the majority of carcasses contaminated with the bacteria, but 37% of carcasses contained between 1 and 3.9 log CFU/100 cm 2 .…”

Detection of &lt;i&gt;Salmonella enterica&lt;/i&gt; Serovar Rissen in Slaughter Pigs in Northern Ireland

“…Rissen is a commonly reported serotype around the world and it is amongst the top three serotypes found in pigs and pork products in Europe and Southeast Asia [3]. Numerous studies have identified S. Rissen in slaughtered pigs in Portugal [4] and within pig fattening units and from slaughter-age pigs and Spain [5] [6] [7] [8] [9].…”