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Chapter 6 6.10. Conclusions and recommendations This work indicates no clear repeatable consistent differences between the S. Agona outbreak strain SAGOXB.0066 and other strains within S. Agona in terms of density of biofilm using the standard biofilm development methods. However, this work did demonstrate that given adequate access to growth area and nutrients all of the Salmonella strains were able to readily form a biofilm at room temperature on all surfaces tested. Furthermore, the strains of Salmonella examined were able to continue to proliferate over an extended period of time using the CBR method. It is plausible that any of the strains studied could lead to a large food-borne outbreak if not eliminated entirely through disinfection. It has also been demonstrated that it is difficult to eradicate all viable cells from a preestablished biofilm. This was also suggested from the findings of previous studies relating to Salmonella Agona outbreaks including the SAGOXB.0066 outbreak. Therefore, it may be best to conclude that prevention of the introduction of Salmonella and the establishment of biofilm in a food processing environments is critical, as the biofilm may be difficult, if not impossible to eradicate with available methods once well established over time. Page 217
Chapter 6 6.11. Further research This research has highlighted many areas that would benefit from further investigation. It would have been of interest to investigate other areas surrounding this project such as the biofilm density of more S. enterica strains involved in food-borne outbreaks and sequenced strains. Additionally, it may have been of interest to investigate Salmonella competition and survival in the presence of other bacterial strains associated with food processing environments such as Pseudomonas [70]. However the major constraint of the CBR method is the limitation of 1 strain per experiment which may last for the duration of 1-2 weeks, depending on conditions. Moreover, in order to confirm repeatability and validate findings it is best practice that the results are reproduced on a number or repeated experiments which also adds to the length of time needed to attain results. The cost associated with the use of multiple reactors and the labour intensive method also limits the number of reactors that can be maintained simultaneously. Furthermore, a second area of interest would be to perform a complete genomic analysis of the Salmonella strains of interest. As discussed in chapter 1, there are a number of key genomic cues involved in Salmonella biofilm development. This has been studied and reviewed to a great extent elsewhere [28]. However, similar to what has been reported in this research, relating to biofilm substrata and reactor models, the majority of the research has been performed on a limited number of strains, serovars or using a basic microtitre plate model. While the microtitre based model has advantages of high-throughput assessment of a large number of strains simultaneously, it has clearly been demonstrated in this thesis that surface substrata and biofilm conditions such as duration of biofilm development can have a major impact on biofilm density. Ideally, if there were no limitations on time and cost, a full genomic analysis through microarray Page 218
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Salmonella enterica - biofilm forma
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Table of Contents Page Number 1.16.
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Table of Contents Page Number 4.1.2
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Table of Contents Page Number 6.8.4
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List of Abbreviations Table Page Nu
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List of Abbreviations List of Abbre
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Summary of Content Summary of Conte
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“To show your true ability is alw
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Acknowledgements ever met, Fiona th
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Acknowledgements This Ph.D. thesis
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Chapter 1 1.1. Salmonella Salmonell
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Chapter 1 may impose enormous costs
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Chapter 1 cracks or penetration of
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Chapter 1 detected by agglutination
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Chapter 1 become colonized with >10
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Chapter 1 antigens [z27],[z45] [1].
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Chapter 1 S. Agona has also been im
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Chapter 1 isolated from undercooked
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Chapter 1 The S. Typhimurium strain
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Chapter 1 ecosystem with the use of
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Chapter 1 [82]. Previous research h
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Chapter 1 to genes involved in flag
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Chapter 1 observation has also been
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Chapter 1 [119] and flow cell react
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Chapter 1 based disinfectant) the s
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Chapter 1 formation of two strains
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Chapter 1 shield the S. Agona cells
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Chapter 1 Key Objectives of this st
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Chapter 2 2. Abstract Food-borne pa
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Chapter 2 indicated that there may
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Chapter 2 taken from industrial set
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Chapter 2 2.1.4. CDC Biofilm Reacto
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Chapter 2 can be performed without
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Chapter 2 To summarise, previous au
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Chapter 2 2.3. Methods for examinin
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Chapter 2 and the biofilm formed th
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Chapter 2 2.4. Statistical Analysis
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Chapter 2 Table 2.1: Strain charact
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Chapter 2 XII. The gas port and med
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Chapter 2 II. Primary fixative cons
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Chapter 2 IX. Once the conditions w
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Chapter 2 Figure 2.1: Image of CBR
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Chapter 2 2.6. Results 2.6.1. Asses
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Chapter 2 2.6.3. SEM Analysis of su
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Chapter 2 Figure 2.6: Complete remo
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Chapter 2 2.6.5. Mean log 10 densit
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Chapter 2 2.6.6. Mean log 10 densit
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Chapter 2 Table 2.5: Mean log 10 de
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Chapter 2 The results displayed in
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Chapter 2 Table 2.7: Difference bet
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Chapter 2 Table 2.8: The mean log 1
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Chapter 2 Figure 2.7: Graph of the
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Chapter 2 also used “high” soni
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Chapter 2 2.8. Summary All 13 strai
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Chapter 3 3. Abstract It has been e
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Chapter 3 classified as persistent
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Chapter 3 was plated onto TSA for e
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Chapter 3 Figure 3.1: The mean log
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Chapter 3 Figure 3.3: SEM image of
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Chapter 3 Table 3.2: Difference bet
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Chapter 3 3.4.3. Intra-serovar vari
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Chapter 3 3.4.4. Strain variation i
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Chapter 3 3.4.5. The density of bio
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Chapter 3 3.5. Discussion As illust
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Chapter 3 As discussed in section 3
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Chapter 3 increased biofilm appeare
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Chapter 4 Examining the efficacy of
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Chapter 4 through laboratory based
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Chapter 4 acid and quaternary ammon
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Chapter 4 the surface the temperatu
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Chapter 4 availability of multiple
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Chapter 4 peracetic acid (100, 200,
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Chapter 4 As discussed previously,
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Chapter 4 Dey/Engley (Difco) neutra
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Chapter 4 sterilisation was achieve
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Chapter 4 IX. Aliquots of 100µl of
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Chapter 4 XV. XVI. XVII. XVIII. XIX
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Chapter 4 4.3. Results 4.3.1. Suspe
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Chapter 4 Table 4.3: Mean log 10 de
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Chapter 4 Benzalkonium chloride was
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Chapter 4 4.4. Discussion Suspensio
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Chapter 4 effective at eliminating
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Chapter 4 Surprisingly, Nguyen et a
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Chapter 4 though a contact time of
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Chapter 4 provide a more standardis
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Chapter 4 hours instead of the stan
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Chapter 5 5. Abstract Examining bio
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Chapter 5 dry and rough (bdar) morp
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Chapter 5 absence of curli and cell
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Chapter 5 studies such as the micro
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Chapter 5 discussed in chapter 4. T
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Chapter 5 5.2. Methods 5.2.1. Colon
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Chapter 5 XIII. XIV. XV. XVI. XVII.
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Page 198 and 199: Chapter 5 5.3.4. The density of bio
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Page 204 and 205: Chapter 5 Table 5.8: Summary of ass
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Page 214 and 215: Chapter 6 Discussion of S. enterica
Page 216 and 217: Chapter 6 However, a number of auth
Page 218 and 219: Chapter 6 It is of interest to exam
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Page 222 and 223: Chapter 6 attributable to a small n
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Page 230 and 231: Chapter 6 Moreover, based on the re
Page 232 and 233: Chapter 6 responsible for increased
Page 234 and 235: Chapter 6 not fully capture the ran
Page 236 and 237: Chapter 6 However, the extent of bi
Page 240 and 241: Chapter 6 studies may solve some of
Page 242 and 243: Bibliography Bibliography Page 221
Page 244 and 245: Bibliography 12. T. Takata, J.L., H
Page 246 and 247: Bibliography 29. Barker, J., M. Nae
Page 248 and 249: Bibliography 47. Threlfall, E.J., H
Page 250 and 251: Bibliography 65. CDC. Investigation
Page 252 and 253: Bibliography 83. Ledeboer, N., Frye
Page 254 and 255: Bibliography 100. Chia, T., Goulter
Page 256 and 257: Bibliography 117. Buckingham-Meyer,
Page 258 and 259: Bibliography 133. European Committe
Page 260 and 261: Bibliography Supernatant of a Hafni
Page 262 and 263: Bibliography 165. Díez-García, M.
Page 264 and 265: Bibliography cultivation of Staphyl
Page 266 and 267: Bibliography Compounds. 2012. Appli
Page 268 and 269: Bibliography 215. Buck, et al., A q
Page 270 and 271: Bibliography Canadian Journal of Ps
Page 272 and 273: Appendix 1 Appendix 1— List of Re
Page 274 and 275: Appendix 1 Appendix 1 - List of Equ
Page 276 and 277: Appendix 2 Colour index High outlie
Page 286 and 287: Appendix 3 Appendix 3-Figure 2: PFG
Page 288 and 289:
Appendix 4 Poster Presentation Envi
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