A systematic review of studies on Escherichia coli and Enterobacteriaceae on beef carcasses at the slaughterhouse

Abstract

European legislation has defined as process hygiene criteria for the main livestock species (cattle, sheep, goats, horses and pigs) the monitoring of aerobic colony count and Enterobacteriaceae. Detected values above the defined criteria require an improvement in slaughter hygiene and the review of process control. The main source of microbiological contamination of beef carcasses along the slaughterline is of fecal origin, therefore Escherichia coli and Enterobacteriaceae seem to be the most suitable indicators to assess the hygienic status of the slaughter process. Although microbiological criteria addressing indicator bacteria have been in place in industrialized countries for several years, scattered information still exists on factors affecting their counts on beef carcasses along the slaughterline. Therefore, a systematic literature review, covering the period 2000-2012, was conducted to gather information concerning: 1) counts of E. coli and Enterobacteriaceae on beef carcasses linked to different stages of the slaughterline; 2) factors influencing presence/counts of E. coli and Enterobacteriaceae on beef carcasses; and 3) the relationship between indicator bacteria (E. coli and Enterobacteriaceae) counts and visual fecal contamination of beef carcasses. According to the 41 retrieved papers the following conclusions were drawn. A decrease of the indicator bacteria counts was recorded after sequential decontamination treatments, such as pasteurization and hot water washing. Slaughterhouse characteristics influenced bacterial load of beef carcasses, although it was difficult to assess which factors (i.e., slaughterhouse throughput, design of the plant, surveillance system in place) had the greatest effect. Finally, carcasses from fecal contaminated animals had higher bacterial loads than those from clean animals. Therefore, the development of a visual classification system of the level of dirtiness of carcasses and the application of effective treatments on the carcasses classified as dirty along the slaughterline can lead to a contamination level for these carcasses comparable to or lower than that of originally clean ones at the end of the slaughterline.

Keywords: Fecal contamination; Indicator bacteria; Risk factors; Slaughter process.