Predictive modelling of the growth of Campylobacter jejuni in chilled chicken during transportation for the purposes of ‘biosensor’ based consumer safety monitoring

Hall, James Martin (2015) Predictive modelling of the growth of Campylobacter jejuni in chilled chicken during transportation for the purposes of ‘biosensor’ based consumer safety monitoring. Masters by Research thesis (MSc), Manchester Metropolitan University.

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Abstract

In the EU annually, an estimated 9 million people suffer from Campylobacter Spp. related food poisoning, with a loss of productivity in the region of 2.4 billion Euros. A Gram-negative bacteria about which little is known outside commercial broiler chicken rearing, the proliferation of campylobacter on fresh chilled chicken produce as a result of temperature abuse in the supply chain is considered to represent a significant risk to consumer health. The current study employed both culture-based methodology and real time polymerase chain reaction (RT-PCR) analysis to determine the population dynamics of Campylobacter jejuni ATCC-33291 on raw chilled chicken produce when packaged under those vacuum and modified atmosphere packaging (MAP) conditions commonly employed in the control of bacterial spoilage. Bacterial growth or decline was determined at 4oC, 10oC, 20oC, 30oC, 37oC and 42oC; reflecting both the typical range of temperature abuse in transit and facilitating comparison with the published literature. Regression analysis of the experimentally derived data was employed to construct a digital model of campylobacter population dynamics; enabling the prediction of bacterial proliferation, and in turn consumer safety, for any given combination of packaged chilled chicken produce and temperature breach parameters. Digital modelling of the RT-PCR analysis derived data indicates an increase in campylobacter DNA copy number at temperatures of 20oC and 30oC, not reflected in the equivalent enumeration by culture-based microbiology. This observed disparity may reflect a cycling bacteria population or the expression of exogenous bacterial DNA, and indicates a requirement to define the pathology of campylobacteriosis in relation to biofilm structural components. Modelling of Vibrio Spp. experimentally isolated from chicken produce highlights both a necessity to characterise bacterial proliferation within a range of campylobacter strains representative of those present in chilled chicken produce, and indicates a role for RT-PCR based campylobacter identification within both poultry produce monitoring and clinical isolation. Although requiring characterisation, determination of residual gas in MAP packaging shows a significant difference in CO2 content between control and samples inoculated with C. jejuni ATCC-33291 when incubated at 30oC. Further definition may indicate an application for gas analysis in the detection of campylobacter proliferation in retail packaging, in conjunction with digital proliferation modelling, or as a standalone system. The feasibility of methodology for the generation, integration and digital modelling of bacterial proliferation is discussed, in the context of a temperature and humidity logging tracking system with empirical decision making capability in relation to consumer safety, biosecurity and product origination. Shortcomings in the understanding of Campylobacter Spp. lifecycle and host colonisation routes are discussed, serving to highlight an opportunity to both build on the current knowledge of food borne pathogens and form a direct scientific basis for the direction of consumer safety measures.