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Chapter 1 observation has also been reported previously. Evans et al., detailed how consecutive outbreaks of S. Enteritidis PT4 were traced back to baking equipment [109]. Stocki et al. hypothesised that Salmonella colonization and persistence on egg conveyor belts can be attributed to the surface type (plastic, vinyl, nylon, hemp-plastic) more than the presence of the rdar morphotype (physiological adaptation commonly associated with Salmonella biofilm formation) [67]. 1.15.4. Methods for Biofilm analysis Numerous research projects have focussed on the use of the microtitre plate system for the assessment of biofilm formation due to its high throughput nature and ease of use [56, 86, 96, 110-113]. In brief, the test organisms are grown in a microtitre plate at optimal temperature in the presence of a nutrition source (usually Tryptic Soy Broth or Luria-Bertani Broth) for 2-28 days (depending on experimental design). After the biofilm has formed on the surface the density of cellular attachment is quantified by reading optical density after indicator dye has been added (such as crystal violet). This biofilm method is static (no consistent flow of nutrients) therefore it may not reflect real-life conditions of biofilm in industry where a biofilm may generally be in contact with flow of liquids and nutrients. Also, the surface properties of the polystyrene microtitre plate systems may not reflect the stainless steel, glass and concrete surfaces usually found in many industrial food processing areas [107]. The Minimum Biofilm Eradication Concentration (MBEC) previously referred to as the Calgary device [114] was designed as a suitable alternative to the microtitre plate method. The lid of the plate is set with 96 individual plugs that can fit into the each well of a 96 well microtitre plate. The plugs can be coated with a particular finish of material (i.e. Page 25
Chapter 1 concrete) and aseptically removed from the lid of the microtitre plate after biofilm formation. The plugs are then used for enumeration via plate counts or for evaluation by direct microscopy. Another high throughput assay for assessing biofilm formation has been devised using a BioFilm Ring Test ®. The biofilm ring test is based on placing magnetic beads (toner) in a high concentration of a test organism, which is then allowed to develop into a biofilm by incubating the organism in a microtitre plate. After the incubation period, the microtitre plate is placed on a magnetic support block [115]. The hypothesis is that if a biofilm is formed it will not allow the magnetic beads to agglutinate at the centre of the microtitre plate [115]. An additional alternative to the microtitre plate system is the insertion of coupons made of the relevant materials into 6/24 well microtitre plates [71, 98]. This method allows biofilm growth and direct visualisation of the process through microscopy. Similarly nutrient media is spiked with a known concentration of bacterial culture and allowed to grow at optimal temperatures. After the biofilm has grown, the coupons can be assessed with microscopy or the viable colony counting though plate count methodology. However this procedure still does not account for sheer stress which can result in greater attachment, increased biomass and higher physiological activity than a biofilm grown in laminar flow or batchphase models [116-117]. In order to overcome this issue, some researchers have chosen to examine biofilm formation in a modified Robbins device [118], which allows nutrients to flow through the device and come into contact with the surfaces that are inserted into the ports. The device is connected to fresh media via tubing which allows continuous flow of nutrients and waste disposal. The biofilm forms on the surfaces which can then be removed for further analysis (microscopy or plate counts). Similar Plug Flow devices Page 26
Page 1: Salmonella enterica - biofilm forma
Page 4 and 5: Table of Contents Page Number 1.16.
Page 6 and 7: Table of Contents Page Number 4.1.2
Page 8 and 9: Table of Contents Page Number 6.8.4
Page 10 and 11: List of Abbreviations Table Page Nu
Page 12 and 13: List of Abbreviations List of Abbre
Page 14 and 15: Summary of Content Summary of Conte
Page 16 and 17: “To show your true ability is alw
Page 18 and 19: Acknowledgements ever met, Fiona th
Page 20 and 21: Acknowledgements This Ph.D. thesis
Page 22 and 23: Chapter 1 1.1. Salmonella Salmonell
Page 24 and 25: Chapter 1 may impose enormous costs
Page 26 and 27: Chapter 1 cracks or penetration of
Page 28 and 29: Chapter 1 detected by agglutination
Page 30 and 31: Chapter 1 become colonized with >10
Page 32 and 33: Chapter 1 antigens [z27],[z45] [1].
Page 34 and 35: Chapter 1 S. Agona has also been im
Page 36 and 37: Chapter 1 isolated from undercooked
Page 38 and 39: Chapter 1 The S. Typhimurium strain
Page 40 and 41: Chapter 1 ecosystem with the use of
Page 42 and 43: Chapter 1 [82]. Previous research h
Page 44 and 45: Chapter 1 to genes involved in flag
Page 48 and 49: Chapter 1 [119] and flow cell react
Page 50 and 51: Chapter 1 based disinfectant) the s
Page 52 and 53: Chapter 1 formation of two strains
Page 54 and 55: Chapter 1 shield the S. Agona cells
Page 56 and 57: Chapter 1 Key Objectives of this st
Page 58 and 59: Chapter 2 2. Abstract Food-borne pa
Page 60 and 61: Chapter 2 indicated that there may
Page 62 and 63: Chapter 2 taken from industrial set
Page 64 and 65: Chapter 2 2.1.4. CDC Biofilm Reacto
Page 66 and 67: Chapter 2 can be performed without
Page 68 and 69: Chapter 2 To summarise, previous au
Page 70 and 71: Chapter 2 2.3. Methods for examinin
Page 72 and 73: Chapter 2 and the biofilm formed th
Page 74 and 75: Chapter 2 2.4. Statistical Analysis
Page 76 and 77: Chapter 2 Table 2.1: Strain charact
Page 78 and 79: Chapter 2 XII. The gas port and med
Page 80 and 81: Chapter 2 II. Primary fixative cons
Page 82 and 83: Chapter 2 IX. Once the conditions w
Page 84 and 85: Chapter 2 Figure 2.1: Image of CBR
Page 86 and 87: Chapter 2 2.6. Results 2.6.1. Asses
Page 88 and 89: Chapter 2 2.6.3. SEM Analysis of su
Page 90 and 91: Chapter 2 Figure 2.6: Complete remo
Page 92 and 93: Chapter 2 2.6.5. Mean log 10 densit
Page 94 and 95: Chapter 2 2.6.6. Mean log 10 densit
Page 96 and 97:
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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Chapter 5 XVI. XVII. XVIII. XIX. XX
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Chapter 5 5.3.2. Repeatability of m
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Chapter 5 Figure 5.2: Stained biofi
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Chapter 5 was formed at room temper
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Chapter 5 Table 5.3: The density of
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Chapter 5 5.3.4. The density of bio
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Chapter 5 Table 5.6: The difference
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Chapter 5 Table 5.7: The difference
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Chapter 5 Table 5.8: Summary of ass
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Chapter 5 interpretation therefore
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Chapter 5 measures of S. enterica b
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Chapter 5 cells peaks [165, 191]. D
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Chapter 5 5.5. Limitations of the s
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Chapter 6 Discussion of S. enterica
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Chapter 6 However, a number of auth
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Chapter 6 It is of interest to exam
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Chapter 6 were similar at 48 hours.
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Chapter 6 attributable to a small n
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Chapter 6 chosen as an appropriate
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Chapter 6 undetermined. However, th
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Chapter 6 reason for this may be du
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Chapter 6 Moreover, based on the re
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Chapter 6 responsible for increased
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Chapter 6 not fully capture the ran
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Chapter 6 However, the extent of bi
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Chapter 6 6.10. Conclusions and rec
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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
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Bibliography 29. Barker, J., M. Nae
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Bibliography 47. Threlfall, E.J., H
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Bibliography 65. CDC. Investigation
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Bibliography 83. Ledeboer, N., Frye
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Bibliography 100. Chia, T., Goulter
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Bibliography 117. Buckingham-Meyer,
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Bibliography 133. European Committe
Page 260 and 261:
Bibliography Supernatant of a Hafni
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Bibliography 165. Díez-García, M.
Page 264 and 265:
Bibliography cultivation of Staphyl
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Bibliography Compounds. 2012. Appli
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Bibliography 215. Buck, et al., A q
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Bibliography Canadian Journal of Ps
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Appendix 1 Appendix 1— List of Re
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Appendix 1 Appendix 1 - List of Equ
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Appendix 2 Colour index High outlie
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Page 280 and 281:
Page 282 and 283:
Page 284 and 285:
Page 286 and 287:
Appendix 3 Appendix 3-Figure 2: PFG
Page 288 and 289:
Appendix 4 Poster Presentation Envi
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