Escherichia coli and Enterobacteriaceae counts on pig and ruminant carcasses along the slaughterline, factors influencing the counts and relationship between visual faecal contamination of carcasses and counts: a review
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A literature review was conducted covering the period 2000-2012 to gather information concerning the presence and counts of E. coli and Enterobacteriaceae on carcasses of main livestock species during different stages of the slaughterline (review question 1); risk factors that could explain the variability of the counts of the indicator organisms (review question 2) and the relationship between the counts of indicator organisms and visual faecal contamination on carcasses (review question 3). In total, 86 papers considering the main livestock species (cattle, pigs, sheep and goats) with the exception of poultry, and providing pertinent data for the scopes of the search, were retrieved. In relation to review question 1, the steps of the processing line where a decrease of indicator bacteria was more evident were: sequential decontamination treatments such as pasteurization and hot water washing applied before chilling for cattle; scalding and also according to some authors, pasteurization and chilling for pigs, plus chilling and pasteurization for small ruminants. Concerning review question 2, most of the retrieved studies investigated risk factors related to slaughtering process. Hot water washing and steam pasteurization were clearly effective in reducing bacterial load on beef carcasses. Hot water treatments were effective also for pig carcasses. The dressing technique and pasteurization treatment were described as factors able to control bacterial contamination of small ruminant carcasses. In relation to review question 3, only studies providing data about ruminants were available and the reported results confirmed that the presence of visible faecal contamination led to higher bacterial loads on carcasses of dirty animals than those obtained from clean animals and the application of additional hygienic measures can be effective in order to reduce bacterial load of contaminated carcasses at the end of the processing line.