ReviewDo any spray or dip treatments, applied on broiler chicken carcasses or carcass parts, reduce Salmonella spp. prevalence and/or concentration during primary processing? A systematic review–meta-analysis
Introduction
Broiler carcass treatments with a spray or dip are disinfecting practices implemented during broiler chicken processing after de-feathering and evisceration and before or after carcass chilling (Stopforth et al., 2007). Disinfectants could be of physical (e.g. hot water or steam), chemical (e.g. chlorine or organic acids) or biological (e.g. bacteriophages or bacteriocins) nature (Hugas & Tsigarida, 2008; Loretz, Stephan, & Zweifel, 2010) with reported efficacy ranging from 0.7 to 2.5 log10 reductions in concentration depending on the disinfectant type and application conditions (Northcutt, Smith, Musgrove, Ingram, & Hinton, 2005; Wang, Li, Slavik, & Xiong, 1997). The added efficacy of chemical and biological disinfectants over water has been considerably debated for spray washing applications since it is believed that the physical action from the spray alone will result in a sufficient removal of Salmonella from carcasses (Northcutt et al., 2005; Wang et al., 1997).
Systematic review (SR)–meta-analysis (MA) methodology offers a structured and repeatable format for identifying and appraising intervention research, and synthesizing, when appropriate, results from multiple, sufficiently similar studies using a quantitative MA (Borenstein, Hedges, Higgins, & Rothstein, 2009). The summary effect estimates are more precise and informative for end users of ‘intervention efficacy’ information, particularly if generated from a reasonable numbers of studies (n > 20 studies) and in the absence of statistically significant heterogeneity and publication bias.
Our objective was to evaluate the efficacy of various broiler chicken carcass spray or dip treatments on Salmonella prevalence or concentration (measured at the carcass level) from slaughter to primary chilling using SR–MA methods.
Section snippets
Methods
This study emerged from a large scoping study that investigated global published intervention, risk factor and prevalence research on Salmonella in broiler chicken. The efficacy of various on-farm and processing interventions, identified and prioritized at the scoping stage (Farrar, 2009), was investigated through multiple, separate SR–MAs, reported elsewhere (Bucher et al., 2011). The review protocol was developed a priori and pre-tested at the scoping stage, prescribing replicable procedures
Study inclusion and their characteristics
From 81 potentially relevant studies, 14 spray and 16 dip studies were found eligible for MA. Most of the 81 studies (n = 26) were excluded due to insufficiently reported results and dissimilar treatments (n = 11) (Fig. 1). The descriptive characteristics of the eligible studies are presented in Table 1. Thirty-six studies were excluded at the BA/MA stage, primarily due to insufficient data to conduct MA (26 studies), non-replicable intervention protocols (three studies), or a lack of control group
Discussion
Meta-analysis of trials investigating TSP dip treatments found no significant difference in the odds of Salmonella contamination for TSP dipped samples compared to samples dipped in potable water or buffered peptone water. Five of the trials included in this MA reported increases in Salmonella contamination, four reported reductions in Salmonella contamination and three reported no difference in contamination frequency between treated and control samples. These varied results may be due to
Conclusions
Meta-analysis of trials investigating TSP dips found that the treatments had no effect on the odds of Salmonella contamination compared to buffered peptone water or water dips. Significant heterogeneity in trials investigating various spray treatments (TSP, AEO water, CPC, LA, NaBis and potable water) limits the interpretation of their summary estimates, however overall trends in the data suggest that these treatments may be effective at reducing the concentration of Salmonella in broiler
Acknowledgements
The authors would like to thank the Ontario Ministry of Agriculture Food and Rural Affairs, the Poultry Industry Council and the Public Health Agency of Canada for funding. We would also like to thank Dr. Bob Wills, Dr. Hart Bailey, Lars Plym Forshell, Geoff Mead and Sue Reynolds for their expert contributions, Ashley Farrar, Janet Harris, Kyle Burgers, Vi Nguyen, Nanky Rai, Dr. Lea Nogueira Borden, Heather Desjardins, Dr. Vahab Farzan, Dr. Sarah Parker, Dr. Juliana Ruzante, Dr. America Mederos
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