Campylobacter persistence in poultry processing

The Foodborne Illness Reduction Strategy 2018-2021+ released by Australia's Food Regulation Secretariat regards Campylobacter as one of the main foodborne pathogens requiring actions at all points along the food supply chain. The ultimate objective of this thesis was to help poultry processors understand the impact of current processing strategies and develop better hurdle interventions to reduce Campylobacter numbers and prevalence on chicken meat products during slaughter, which may reduce the burden of disease currently associated with this pathogen. Five aims were established for the thesis and included: 1) understanding the impact of current processing interventions on the bacterial numbers and diversity on chicken carcasses throughout commercial processing; 2) mapping changes of the bacterial community on carcasses throughout processing to the end of shelf life and to link the data to the processing environment; 3) developing an in vitro model to test Campylobacter inactivation under mimicked poultry processing conditions; 4) using the in vitro model to evaluate peracetic acid (PAA) as a potential antimicrobial agent in reducing Campylobacter; 5) understanding the potential mechanisms for C. jejuni survival during a 45 min treatment of a sub-lethal of PAA by examining timedependent global proteomic expression. Currently the success of commercial poultry processing lines is measured based on culture-based microbiological analysis, e.g. total bacterial population, count of Campylobacter, etc. This approach is unable to provide information on the entire bacterial community diversity and the importance of Campylobacter in the community in terms of its abundance and relationships with other microbes including those microbes that are not able to be isolated at various processing steps. More recently, the use of chlorine-based disinfectants has been questioned in terms of its effectiveness and potential harm to human health. Looking for alternative processing aids is in demand by the poultry industry and consumers. By completing the aforementioned aims, this thesis will utilise culture-independent techniques along with well-established culture-based methods to fill the gaps outlined, understand indepth the microbial profiles of commercial processing systems and test PAA as a potential antimicrobial aid that could be considered for the replacement of chlorine-based disinfectants. Two different types of poultry processing lines from a single abattoir in Australia, Line A and Line B, were examined. The major differences between Line A and B included: 1) Line A operates with separate steps of scalding, defeathering and plucking, whereas Line B incorporates these three steps together in a confined tunnel, and 2) the time length of immersion chilling (Line A 0.5 h and Line B 1.5 h) and air chilling (Line A 1.5 h and Line B 0.5 h) were different. Both lines produced significant declines (p