A Meta-Analysis Study of the Effect of Chilling on Prevalence of Salmonella on Pig Carcasses

Abstract

In the field of food safety, meta-analysis can be used to combine results of prevalence studies of pathogens at critical stages within the food processing chain so that policy makers can access reliable and concise information on the effectiveness of interventions for controlling and preventing foodborne illnesses in humans. The objective of this work was to demonstrate the applicability of a parametric approach of meta-analysis to the specific case of determining the overall effect of chilling on Salmonella prevalence on pig carcasses. A meta-analysis was performed on each of two parameters measuring effect size for binary outcomes (relative risk and risk difference). Both meta-analyses confirmed that the chilling operation has a significant beneficial effect (P < 0.001) on the reduction of Salmonella prevalence on pig carcasses. Because risk difference is a parameter sensitive to the differences across studies in carcass swab areas and Salmonella detection methods, its meta-analysis highly reflected this heterogeneity (P < 0.001). However, parameterization of relative risk, not being biased by the above sources of variability, did not give rise to heterogeneity among studies and produced a fixed-effects meta-analysis solution, which is deemed more suitable for compilations based on a small number of individual studies (n = 9). Because of the systematic approach of meta-analysis (i.e., individual studies are weighed according to precision) and its reliance for actual data, the output distribution of the relative risk effect size (approximately eN(-0.868,0.166)) merits consideration for inclusion in the chilling stage of quantitative risk assessments modeling the prevalence of this pathogen along the pork production chain.

Role of Slaughtering in Salmonella Spreading and Control in Pork Production

“…At the end of the slaughter line, carcasses are subjected to a chilling process. Although chilling temperatures are not bactericidal for most gram-negative bacteria, Salmonella prevalence has been reported to decrease after chilling procedures (6,11,23,30,92).…”

The assessment of the comparison of the Australian monitoring programme for carcasses to requirements in Regulation (EC) No 2073/2005 on microbiological criteria on foodstuffs

“…There is one report over 4 pig abattoirs that numbers of Enterobacteriaceae decreased after chilling in 3 abattoirs but increased in the other (Lenahan et al, 2009). A meta-analysis study combining results from multiple studies on the effect of chilling on prevalence of Salmonella on pig carcasses indicated that the chilling operation has a significant beneficial effect (P < 0.001) on the reduction of Salmonella prevalence on pig carcasses (Barron et al, 2008). There are published reports indicating that microbial populations on beef carcasses can be reduced by some 0.3-0.7 log during conventional (air) chilling (Nortje and Naude, 1981;Thomas et al, 1977); others reported some 2 log reduction in E. coli counts during 24-36 h of chilling beef carcasses (Bacon et al, 2000).…”

Incidence and prevalence of Vibrio parahaemolyticus in seafood: a systematic review and meta-analysis

“…Hence, researchers can either perform experiment to generate data or utilize available data from previous study (primary study) without experimental work (den Besten and Zwietering 2012 ). It was recently that food safety researchers stated conducting meta analytical studies as most meta-analytical study are conducted only in medical and social sciences (Gonzales Barron et al 2008 ; Gonzales-Barron and Butler 2011 ; Patil et al 2004 ). Meta-analytical studies could be carried out in food safety research in order to help answer various research questions involving prevalence pathogens in foods, treatment interventions, predictive modelling, microbial risk assessement, food safety knowledge, attitude and practices (Xavier et al 2014 ).…”