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Chapter 6 reason for this may be due to only one surface (concrete) contained within the reactor, which may reduce variability due to mixing of surface associated properties contained in the enclosed reactor environment. Alternatively a reason for variation may be due to a less robust methodology in determining the true extent of variation of mean log 10 density. When mean log 10 density was assessed, as described in chapter 2, the mean log 10 density was based on 9 observations (counts performed once on each of 3 coupons x from 3 separate CBR runs) while the method described in chapter 3 was based on 6 observations (counts performed once on each of 3 coupons x from 2 separate runs). The results presented chapter 4 were based on 6 observations (counts performed 3 times on 1 coupon x from each of 2 runs). This change was made to manage the time available to complete the experiments however it also serves to illustrate the extent to which the full extent of variability within a single strain may be underestimated by limitations of methodology. In the latter experiments because of using fewer coupons the difference in repeated measures (represented by SD) was smaller. The use of a larger number of coupons will provide a more comprehensive indication of the ruggedness of the method and the extent of variation between repeated measures of the same strain (repeatability). Therefore multiple measurements are required to confirm apparent differences of biofilm density between strains examined and differences reported based on less robust methods may be questionable. To summarize, the investigation of repeatability of the research performed on multiple contact surfaces using the CBR, measured by SD values, appears to correspond with what has been reported elsewhere. Furthermore the data presented here enhances the understanding of the density of Salmonella enterica biofilm formation through the use of Page 207
Chapter 6 multiple strains and using a number of food contact surfaces simultaneously which help to mimic real life conditions. An unequivocal basis for conclusions regarding phenotypic differences between strains in respect to biofilm formation or biofilm density are an essential preliminary step to studies intended to elucidate molecular studies that underlie such differences. However this requirement is not always met in published studies. One factor contributing to this situation is the workload involved in the phenotypic work. 6.7.2. Ruggedness and Reproducibility The term ruggedness signifies the degree of variability in results (mean log 10 density) after slight modification of the method such as temperature change or flow rate [72]. The research performed by Goeres et al. also indicated that there was slight variation in the mean log 10 density of P. aeruginosa ATCC 700888 biofilm formed depended on the position on the arm within the reactor ranging from 0.08-0.18. The mean log 10 density of P. aeruginosa biofilm was 5.63 ±0.17 CFU cm 2 using the standard protocol. The mean log 10 density also increased when the batch mode increased by 2.4 hours (0.05 cfu/cm 2 ) and a 10% decrease in nutrient concentration resulted in a mean log 10 reduction of 0.10 cfu/cm 2 . Additionally a 2°C increase in temperature increased the mean log 10 density by 0.04 cfu/cm 2 while increasing the rate of revolution of the baffle by 10 rpm increased the mean log 10 density by 0.09 cfu/cm -2 . In total, 21 experiments were performed and the results were assessed on triplicate coupons taken at random from each run. Replicate experiments were undertaken to investigate the reproducibility under each alternative set of conditions. Overall, the research on optimizing conditions for the use of the CBR suggest that the method was reproducible and sufficiently rugged to withstand slight modification of the procedure [72, 236]. Page 208
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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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Page 184 and 185: Chapter 5 5.2. Methods 5.2.1. Colon
Page 186 and 187: Chapter 5 XIII. XIV. XV. XVI. XVII.
Page 188 and 189: Chapter 5 XVI. XVII. XVIII. XIX. XX
Page 190 and 191: Chapter 5 5.3.2. Repeatability of m
Page 192 and 193: Chapter 5 Figure 5.2: Stained biofi
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Page 198 and 199: Chapter 5 5.3.4. The density of bio
Page 200 and 201: Chapter 5 Table 5.6: The difference
Page 202 and 203: Chapter 5 Table 5.7: The difference
Page 204 and 205: Chapter 5 Table 5.8: Summary of ass
Page 206 and 207: Chapter 5 interpretation therefore
Page 208 and 209: Chapter 5 measures of S. enterica b
Page 210 and 211: Chapter 5 cells peaks [165, 191]. D
Page 212 and 213: Chapter 5 5.5. Limitations of the s
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 236 and 237: Chapter 6 However, the extent of bi
Page 238 and 239: Chapter 6 6.10. Conclusions and rec
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
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Appendix 2 Colour index High outlie
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Appendix 3 Appendix 3-Figure 2: PFG
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Appendix 4 Poster Presentation Envi
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