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Chapter 6 responsible for increased variation between experiments which further demonstrates the importance of confirming removal from the surface. Giaouris et al. also noted incomplete removal of a 168 hour S. Enteritidis biofilm attached to stainless steel [188]. However, as described in chapter 3, the used of conductance measurement in broth may also have certain limitations. In the absence of direct visualisation to confirm biofilm removal from the surface, researchers should be aware that reporting a mean log 10 density of biofilm or a reduction in density of viable cells after treatment, solely reflects the cells removed from the surface [183]. Previous authors have described the use of sonication to remove biofilm for enumeration purposes without providing evidence that the entire biofilm was removed from the surface [71-72, 114, 118, 122, 124]. 6.8.3. Biofilm density variability using the microtitre plate based method As described extensively in chapter 5, the SD of the OD 590 readings suggests a substantial range in values of the repeated measurement. The SD of the mean using the microtitre plate method was substantially higher than the SD reported with the CBR, as detailed in chapters 2 and 3. This indicates that limitations of repeatability of the microtitre plate method, as applied here, are such as to limit the application of the method for quantitative purposes. Similar variation on repeated measurements of optical density has been reported elsewhere using the microtitre plate model described in this thesis [56, 96, 191]. A number of authors chose to use the standard error (dividend of standard deviation) rather than the standard deviation to display the differences in repeated measurements [56, 96]. However the use of standard errors to demonstrate variance between repeated experiments is not recommended [233-234]. It is also useful to note that the mean and SD values reported in this thesis were calculated on 3 replicates test wells of three independent experiments (n=9), while Page 211
Chapter 6 previously published material has published on 3 replicate wells from one experiment or have not provided the figures to examine the extent of variation in tabular format (graphs only) [56, 178]. 6.8.4. Reasons for variation using the microtitre plate bases system As discussed in the limitations of the research performed in chapter 5, there may be a number of reasons for this variation in SD values. First, it was evident from repeated examination that the optical density reader may not provide consistent values even on repeated examination of the same microtitre plate (see Table 5.1 in chapter 5 and Table 1 in Appendix 2 for details). It is also possible that slight variation in the position held in the automated reader may result in a different area going under examination. Low speed shaking of the inoculated microtitre plates during incubation may alleviate some aggregation of biofilm cells, however the aggregation may also represent the heterogeneous formation of macro-colonies on the surface. Moreover, post staining with crystal violet, it was apparent that the crystal violet stain was not completely eluted from the biofilm uniformly across the entire surface of the plate. It is possible that the use of other reagents such as glacial acetic acid [111-112, 135, 165] instead of ethanol: acetone may have been more effective. Others have achieved greater repeatability using this method [111-112, 165]. Due to time constraints this method could not optimized for the research presented in chapter 5. 6.8.5. The limitations of using repeated measurements Although the level of repeatability presented in this work, broadly corresponds to what has been reported elsewhere, there is still a need to exercise caution when interpreting results. Due to the small sample size (6- 9 observation in most comparisons of individual strains), the findings may Page 212
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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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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
Page 194 and 195: Chapter 5 was formed at room temper
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Page 198 and 199: Chapter 5 5.3.4. The density of bio
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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 226 and 227: Chapter 6 undetermined. However, th
Page 228 and 229: Chapter 6 reason for this may be du
Page 230 and 231: Chapter 6 Moreover, based on the re
Page 234 and 235: Chapter 6 not fully capture the ran
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 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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