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dc.contributor.authorZhilyaev, Samsonen_US
dc.date.accessioned2017-12-13T07:00:50Z
dc.date.available2017-12-13T07:00:50Z
dc.date.issued2016-06-20en_US
dc.identifier.othervt_gsexam:8064en_US
dc.identifier.urihttp://hdl.handle.net/10919/81184
dc.description.abstractA Quantitative Microbial Risk Assessment (QMRA) has been undertaken to utilize research on Shiga-toxin Escherichia coli (STEC) contamination in beef for the benefit of public health. The QMRA operates as a 2nd order Monte Carlo simulation to create stochastic mathematical models that incorporate all of the key components of STEC contamination from farm to fork. The resulting model is able to identify knowledge gaps, public health risks, and simulate theoretical changes in the beef system. However, high variability in processing plant intervention literature has prompted a meta-analysis to determine informed estimates of intervention effectiveness for QMRA parameterization. Meta-analysis derived least-squares means bacterial log reductions for acetic acid, lactic acid, steam vacuum, and water wash interventions on carcass surfaces (n=249) were 1.44 [95% CI: 0.73 – 2.15], 2.07 [1.48 – 2.65], 3.09 [2.46 – 3.73], and 1.90 [1.33 – 2.47] log CFU/cm2, respectively. Least-squares means log reductions for acetic acid, lactic acid, sodium hydroxide, and water wash on hide surfaces (n=47) were 2.21 [1.36 – 3.05], 3.02 [2.16 – 3.88], 3.66 [2.60 – 4.72], and 0.08 [-0.94 – 1.11] log CFU/cm2, respectively. Meta-regressions showed that temperature, duration of application, microbial starting concentration, extra water washes, inoculation type, organism type, sample method, surface type, and antimicrobial concentrations were all significant predictors of intervention effectiveness. Finally, after observing authors use substituted values for samples found below a detection limit in primary plant intervention literature, simulations were run to assess the impact of substitution on a random-effects meta-analysis. Simulation results show that substitution practices artificially decrease effectiveness estimates and increase heterogeneity.en_US
dc.format.mediumETDen_US
dc.publisherVirginia Techen_US
dc.rightsThis Item is protected by copyright and/or related rights. Some uses of this Item may be deemed fair and permitted by law even without permission from the rights holder(s), or the rights holder(s) may have licensed the work for use under certain conditions. For other uses you need to obtain permission from the rights holder(s).en_US
dc.subjectQMRAen_US
dc.subjectmeta-analysisen_US
dc.subjectEscherichiaen_US
dc.subjectcolien_US
dc.subjectO157en_US
dc.subjectmeta-regressionen_US
dc.subjectplanten_US
dc.subjectinterventionen_US
dc.subjectbeefen_US
dc.subjectcattleen_US
dc.subjectSTECen_US
dc.titleMeta-Analysis on the Effect of Interventions Used in Cattle Processing Plants to Reduce Escherichia coli Contamination in Beefen_US
dc.typeThesisen_US
dc.contributor.departmentCivil and Environmental Engineeringen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineEnvironmental Planningen_US
dc.contributor.committeechairGallagher, Daniel L.en_US
dc.contributor.committeememberWiddowson, Mark A.en_US
dc.contributor.committeememberSanderson, Michael W.en_US


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