Variability of Escherichia coli and Enterobacteriaceae counts on pig carcasses: A systematic review

Background: Indicator bacteria are considered an interesting target for microbiological analysis in order to obtain information about the hygiene of processes and products. Quantitative analysis targeting in- dicator bacteria offers several advantages over pathogenic bacteria since indicator bacteria prevalence and counts are higher, and their distribution is more homogeneous, than pathogens. However, although microbiological criteria addressing indicator bacteria are already in place in industrialised countries such as the EU and US, information on factors affecting their counts on carcasses at slaughter is scattered. Objectives: The aim of this review was to provide valuable information about the variability of indicator bacteria along the pig slaughterline, and to suggest suitable means for the implementation of GMP (Good Manufacturing Practices) and process hygiene in pig slaughterhouses. Conclusions: Along the slaughterline, scalding and chilling stages effectively reduce both Escherichia coli and Enterobacteriaceae counts on pig carcasses and have to be considered in the implementation of HACCP systems. Surface pasteurisation under experimental slaughter conditions was also effective; in contrast, washing did not reduce microbial contamination on pig carcasses. Evisceration was confirmed as a key contamination point, in particular regarding Enterobacteriaceae, but it has been suggested that bacterial load can be controlled by anal plugging if it is performed according to good manufacturing practices (GMP).