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

European legislation has defined as process hygiene criteria for themain livestock species (cattle, sheep, goats, horses and pigs) themonitoring of aerobic colony count and Enterobacteriaceae. Detected values above the de- fined criteria require an improvement in slaughter hygiene and the reviewof process control. Themain source of microbiological contamination of beef carcasses along the slaughterline is of fecal origin, therefore Escherichia coli and Enterobacteriaceae seemto be themost suitable indicators to assess the hygienic status of the slaughter process. Althoughmicrobiological criteria addressing indicator bacteria have beeninplace inindustrializedcoun- tries 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 car- casses; 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 fromclean 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.