Persistent contamination of Salmonella, Campylobacter, Escherichia coli and Staphylococcus aureus at a broiler farm in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Microbiology at Massey University, Albany, New Zealand
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Date
2017
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Massey University
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Abstract
The public demand for poultry products has increased over the years due to their health benefits and relatively low cost. Intensive production of poultry in broiler farms gives an opportunity for contamination of the birds, thus creating potential foodborne hazards to consumers. Foodborne cases are therefore extensively monitored to implement mitigating strategies to control the outbreaks. Therefore, the main aim of this project was to determine the prevalence and microbial loads of contaminating Campylobacter spp., Salmonella spp., S. aureus and E. coli, in different locations of four broiler sheds at a selected poultry farm in Auckland New Zealand. Standard microbiological methods and multiplex quantitative polymerase chain reaction (qPCR) were used in the analyses. Swab samples were collected in three cycles from March 2016 to June 2016. During each cycle of the cleaning and disinfection regime, 248 swab samples were collected from feeders, feed loaders, drinkers, fans, vents, annex floor, and wall crevices to determine the extent of contamination before cleaning and after disinfection. The collected samples (n = 744) were analysed for the presence of Salmonella spp. and Campylobacter spp. using standard microbiological methods. Suspected isolates of Salmonella spp. were confirmed by latex agglutination test, whilst Campylobacter spp. was confirmed by both latex agglutination and oxidase tests. The swab samples were also analysed for viable S. aureus and E. coli cell counts using Petrifilm™ plates. Multiplex qPCR was developed and validated to enumerate Salmonella spp. and Campylobacter spp. positive
samples.
Results of this study showed that all collected samples were contaminated with Salmonella
spp., Campylobacter spp., S. aureus and E. coli before performing cleaning. After disinfection,
different areas of the shed were still contaminated, posing real danger for infection of the new flock. Crevices and drinkers were the most contaminated areas after disinfection. Organic matter that accumulates in crevices and drinkers during rearing are likely to protect pathogens against disinfectants, which may then contribute to residual contamination and biofilm formation. The ventilation system of the farm was also heavily contaminated. After disinfection, dusts were trapped between the wires of the ventilation screen, making air vents a potential source of contamination in poultry sheds. Feed loaders had higher contamination rates than feeders, even though it was elevated, away from direct contact to birds. When the ventilation system was open, contaminated dusts settle
into various areas of the shed, thereby increasing contamination levels before cleaning, thus
affecting the efficacy of the disinfectant used. Meanwhile, fans and the annex were less
contaminated, indicating that the cleaning regime could effectively disinfect these areas. However,
results showed that microbial concentration in the annex was higher after disinfection. This was
probably caused by the introduction of pathogens from the outside environment, highlighting the
importance of erecting hygiene barriers before entering the main shed.
Multiplex qPCR is an important quantification tool due to its ability to detect, identify and
quantify multiple pathogens in one assay. The standard curves generated from inoculated samples determined the detection limit to be 3.24 - 8.24 Log10 CFU/mL for Salmonella spp., and 2.97 - 7.97 Log10 CFU/mL for Campylobacter spp. respectively. The agreement of results using the standard and qPCR methods was investigated by comparing S. aureus counts obtained from100
environmental samples through Bland-Altman analysis. The two methods showed agreement, but the qPCR was limited to the detection of S. aureus from 3.5 to 6 Log10 CFU/mL. The concentration of Salmonella spp. and Campylobacter spp. enumerated by multiplex qPCR, had no significant difference between the mean counts of each location before cleaning and after disinfection. Concentration of Salmonella spp. and Campylobacter spp. in the samples subjected to analysis by qPCR post-disinfection, were below the detection limit of the method. However, the qPCR method may be suitable for analysis of samples collected before cleaning. Pre-enrichment of samples analysed post-disinfection is recommended to improve the detection and enumeration of Salmonella
spp. and Campylobacter spp. by qPCR analysis.
Description
The following Figures were removed for copyright reasons: Figs 2.6 (=Anya et al., 2014 Fig 1), 2.7 (=Fraga et al., 2008 Fig 10.3.3) & 2.8 (=Marras et al., 2006 Fig 4).
Keywords
Bacterial diseases in poultry, Salmonellosis in poultry, Campylobacter infections in poultry, Escherichia coli infections in animals, Staphylococcus aureus infections, Broilers (Chickens), Microbiology, Food contamination, Research Subject Categories::TECHNOLOGY::Chemical engineering::Food technology