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Chapter 6 Moreover, based on the results presented in this research, the CBR appears to be a much more reproducible method for examining biofilm density that the use of the microtitre plate. However, if there was more time available to work on this project it may have been useful to examine if the extent of variation in repeated measures of biofilm formation using the microtitre plate could be improved by optimizing the formation and enumeration methods as previously discussed in chapter 5. 6.7.3. Heterogeneity of the surfaces. Due to the process of manufacturing certain materials such as concrete the surface roughness may vary even between coupons of the same material. As described in the ISO standard 5725-2:1998(E), the use of sand granules in the manufacturing of concrete means there may be gradation in the size of particles between each sample which may result in slight variation in surface area . In addition, the process of producing bulk materials such as the steel, tile or polycarbonate may also be subject to slight variation between the finished surfaces. Of all five surfaces examined using SEM analysis, glass appeared to be the most homogenous surface. The glass surface also had the smallest standard deviation when surface roughness was assessed using AFM, as described in chapter 2. The surface heterogeneity may contribute to some of the variability observed. However depending on the nature of the experiment and the variability in results, surface heterogeneity may be an important consequence to consider in experimental design. As an example, if the surfaces vary in a laboratory model, it may be reasonable to assume that a similar degree of variability may be present in real life environments. As discussed in chapter 2, the extent of surface roughness may increase the density of biofilm formed on some of the surfaces. Therefore difference in surfaces may need careful consideration when choosing biofilm substrate for research of this nature. Page 209
Chapter 6 6.8. Limitations of the Studies 6.8.1. Incomplete removal of biofilm cells from the surface Scanning electron microscopy was used for all experiments performed using the CBR to assess completeness of biofilm removal from the surfaces by sonication. Based on the evaluation of all 13 strains investigated for biofilm formation over 48 hours, only one strain (S. Typhimurium LT2) was not fully removed using the conditions described in. This finding highlights the need to use SEM or other forms of microscopy to confirm removal of biofilm from a surface which is used for enumeration and comparative purposes as conclusions based on inconsistent removal are more difficult to interpret. 6.8.2. Incomplete removal of the mature biofilm As discussed in chapter 3, sonication under the conditions described was used to maximise removal of biofilm from the surfaces post developed over 168 hours. The results of chapter 2 and 3 indicate that sonication removed more biofilm from the surface than swabbing the surface but that increasing the sonication power or duration was not as effective as it impacted on cell viability. As a result, incomplete removal decreases the validity of using a plate count method to determine the density of 168 hour biofilm attached to the surface. If viable counts are to be applied to assess density of such biofilm then development of acceptable methods to achieve full removal without impairment of cell viability are necessary. An alternative is to work on developing methods that achieve enumeration of viable cells without biofilm detachment such as the use fluorescent staining, which also has certain limitations as discussed in chapter 2. Due to incomplete removal of the 168 hour biofilm, direct comparisons (biofilm log 10 density levels after 48 and 168 hours) should be looked at with a degree of caution. Incomplete but variable removal may be Page 210
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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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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
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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
Page 278 and 279: 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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