Meta-analysis on the Effect of Interventions Used in Cattle Processing Plants to Reduce Escherichia coli Contamination

Introduction: Cattle coming from feed lots to slaughter often harbor pathogenic bacteria that can contaminate final meat products. As a result, reducing contamination during processing is a main priority. Unfortunately plant managers face difficulty when trying to determine optimal intervention strategies from published literature. Intervention literature results and methods vary significantly, making it difficult to implement interventions with any degree of certainty in their effectiveness.

Purpose: To create a more robust understanding of plant intervention effectiveness by performing a formal meta-analysis on plant intervention literature. To assess factors involved in plant intervention effectiveness by explaining heterogeneity.

Methods: Available literature was gathered on popular intervention methods. Intervention effectiveness, measured as raw log reduction, was modelled using study characteristics, such as temperature of application, intervention type, starting microbial concentration, etc.  Least-squares means were calculated for intervention effectiveness separately on hide and on carcass surfaces. Heterogeneity (I²) was assessed and factors influencing intervention effectiveness were identified.

Results: Least-squares mean reductions for acetic acid, lactic acid, steam vacuum, and water wash on post de-hided surfaces (n=223) were 1.58 [95% CI: 0.76 - 2.40], 2.20 [1.46 - 2.94], 2.91 [2.19 - 3.62], and 1.85 [1.14 - 2.55] log CFU/cm², respectively. Least-squares means for acetic acid, lactic acid, sodium hydroxide, and water wash on hide surfaces (n=47) were 2.14 [1.42 - 2.87], 3.05 [2.32 - 3.77], 3.84 [2.94 - 4.73], and 0.11 [-0.79 - 1.01] log CFU/cm², respectively. Heterogeneity, measured as I², was 94% and 92% for the carcass and hide models, respectively. Meta-regressions showed that temperature, pressure, pathogen starting concentration, sample method, surface type, and extra water wash were statistically significant covariates (P<0.10).

Significance: The results allow food safety specialists and risk assessors to evaluate plant intervention effectiveness, variation, and factors more adequately. Development of more robust decontamination procedures is possible, further reducing contamination and illness.