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Title: Colonisation of Poultry by and Subsequent Survival of Salmonella enterica Serovars Isolated from Humans and Foods in Kuwait
Author: Alsaif, Ezdihar
Awarding Body: London South Bank University
Current Institution: London South Bank University
Date of Award: 2013
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Abstract:
Poultry meat is considered to be the major vehicle of foodborne poisoning caused by the Gram-negative bacterium Salmonella. In the Kuwait State, the incidence of human salmonellosis has increased markedly over the last years. The adaptation responses of Salmonella enterica serovars to the current decontamination system used in poultry meat production in Kuwait enhanced their ability to colonise poultry meat and survive the system used in the Kuwait poultry processing plants. A commercial decontamination process is typically applied to remove bacteria from carcasses within a few minutes of chilling. This process usually involves washing the carcasses with a biocidal compound, such as chlorine in the form of sodium hypochlorite (NaOCl), and yet the washing process fails to remove all of the bacteria. This research was designed to investigate the increased colonisation abilities and adaptation responses of Salmonella in order to identify the main attributes of the pathogen in colonisation and survival in the poultry meat and to suggest interventions that could be used to control the organism during processing. This is particularly relevant to Salmonella enterica serovars Typhimurium and Enteritidis, which were found to be the most predominant strains from 2003-2011 among the human and food isolates in Kuwait (mainly raw chicken and cooked chicken products). The molecular typing technique of Pulsed Field Gel Electrophoresis (PFGE) was used in this research to determine the genetic diversity among the Kuwaiti culture collections of human and food isolates. A comparison between S. Typhimurium and S. Enteritidis isolates indicated a high level of genetic relatedness between the human and chicken isolates. The rate of attachment of the bacteria to chicken skin at chill temperature was measured that allowed detailed objective comparisons of the attachment processes under two different conditions, attachment of bacteria before and after exposure to chlorine. The rate of attachment was also compared with that of reference strains from international culture collections. A method to measure the probability of detachment was developed and was applied on the same bacterial strains. The outcome of measuring the attachment and detachment of bacteria to chicken skin showed adaptation responses of representative strains to chlorine, the adaptation that had led to enhanced ability of Salmonella to survive and colonise chicken carcasses. The origin of this adaptation was determined by the microarray technique at the Institute of Food Research, Norwich, UK. The data showed up-regulation of genes associated with oxidative stress response (mutT and icdA), iron stress (YbdZ), biofilm formation and cellulose biosynthesis (bcsG), transport (YgiK), and ribosomal proteins formation (RpsL, RpsQ, and RpsO). In contrast, genes predominantly associated with general cellular metabolism, ribosomal proteins, biofilm formation, flagella biosynthesis and virulence were down-regulated. Findings from this study suggest that the oxidative stress response and the formation of biofilm matrix may render Salmonella resistant to certain types of environmental stresses, which in turn contributes to its survival and persistence in the contaminated poultry meat products This research also includes a review of existing industry practices and control measures applied in the Kuwaiti slaughterhouses to control Salmonella in poultry meat against currently accepted standards such as those in the US, UK and recommended by international agencies. The information collected from selected slaughterhouses and the limited sampling at a number of arbitrarily chosen process steps indicated that there was little effective control and published good practice guidelines were not followed, which would explain the apparent high levels of Salmonella contamination. Given all the shortcomings and poor practices observed in some Kuwaiti slaughterhouses besides the inadequacy of NaOCl to affect a substantial enough reduction in Salmonella contamination in chicken skin, an alternative and more effective decontamination method was investigated. The preliminary study examined the efficacy of combining ultrasound with chlorine treatment on the inactivation of Salmonella inoculated onto the surface of chicken skin under laboratory conditions. Data from this study showed the effectiveness of this combined treatment in reducing the numbers of Salmonella to 2-2.5 log10 cycles with D-value of 30 min than those achieved by either chlorination or sonication alone, suggesting that there could be possible synergistic effects between chlorination and sonication. Findings of this research suggest that there was no major difference between the Salmonella strains isolated from the contaminated chicken meat in Kuwait and the international Salmonella strains in their colonisation, survival and attachment or detachment behaviour on chicken skin. Consequently, the development of HACCP-based food safety management systems, implementation of good hygiene practices and sustained food hygiene training of food handlers should prove to be effective measures to control the colonisation of poultry meat by and subsequent survival of Salmonella in Kuwait.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.593645  DOI: Not available
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