Prevalence and concentration of Escherichia coli O157 in different seasons and cattle types processed in North America: A systematic review and meta-analysis of published research

•Prevalence and levels of E. coli O157 differs by cattle types and seasons.•Prevalence of enumerable hide concentrations is higher at slaughter than the feedlot.•Differences are important for microbial risk assessment modeling. Systematic review (SR) and meta-analyses (MA) methodologies were used to identify, critically evaluate and synthesize prevalence and concentration estimates for Escherichia coli O157 contamination along the beef production chain, and to illustrate differences based on cattle types and seasonality in North America from the scientific peer-reviewed literature. Four electronic databases were searched to identify relevant articles. Two independent reviewers performed all SR steps. Random effects MA models were used to estimate the pooled prevalence and concentration of E. coli O157 in feces, hides and carcasses of cattle processed in North America, including their seasonal estimates. The potential sources of between studies heterogeneity were identified using meta-regression and sub-group analysis. Results indicated differences in the fecal prevalence of E. coli O157 among cattle types: 10.68% (95% CI: 9.17–12.28%) in fed beef, 4.65% (95% CI: 3.37–6.10%) in adult beef, and 1.79% (95% CI: 1.20–2.48%) in adult dairy. Fed beef fecal prevalence was 10.65% (95% CI: 8.93–12.49%) during summer and 9.17% (95% CI: 5.24–13.98%) during the winter months. For adult beef, the fecal prevalence was 7.86% (95% CI: 5.43–10.66%) during summer, and 4.21% (95% CI: 1.95–7.13%) during winter. Among adult dairy, the fecal prevalence was 2.27% (95% CI: 1.5–3.18%) during summer, and 0.36% (95% CI: 0.09–0.74%) during winter. There was a significantly higher percentage of hides with E. coli O157 concentration ≥40CFU/100cm2 on hides of fed beef sampled at the processing plant (23.81%; 95% CI: 14.79–34.15%) compared to those sampled at the feedlot (1.74%; 95% CI: 0.53–3.44%). Prevalence of E. coli O157 on carcass surfaces differed by season only at the post-evisceration stage, but decreased considerably through the subsequent processing stages. Country, study setting, detection method, hide swab area, and study design were identified as significant sources of heterogeneity among studies reporting prevalence of E. coli O157 along the beef production chain. The pooled prevalence and concentration estimates from this study provide a sound and reliable microbiological basis for risk assessment modeling of E. coli O157 and other pathogens in the food chain.