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Chapter 4 availability of multiple models and recommendations tends to result in difficulties with the comparability of data from different studies research. Buckingham-Meyer et al. compared 5 different biofilm test methods. This work used identical glass surfaces to provide biofilm substratum and used a standardised biofilm removal and enumeration method throughout (control coupon–treated coupon). The work evaluated biofilm formation of two strains of P. aeruginosa and S. aureus [117]. The methods varied quite significantly in relation to fluid shear and operation system (batch or continuous flow system). The CDC reactor (as previously described) and a drip flow reactor model (coupons placed in a vertical line in a reactor vessel which comes into contact with a flow of inoculated medium) were used. Other methods included a dehydrated biofilm system (coupons taken out of CDC reactor and dried in accordance to ASTM standards) and the dried surface method (heavy inoculum of test organism allowed dry onto the surface for 2 hours in accordance to the ASTM standards). Buckingham- Meyer suggested that methods such as the dried surface technique and static biofilm method resulted in a ~4 log 10 reduction in the number of viable cells recovered from the surface after contact with sodium hypochlorite. In contrast, after contact with same disinfectant agent there was only a ~1-2 log 10 reduction in the number of cells when the biofilm was formed using the CBR method [117]. This work emphasised the difference in the apparent efficacy of disinfectant products used against the same test strains may be greatly influenced by the method applied. 4.1.5. Disinfectants Used Three disinfectants used for this work sodium hydroxide (1 Mole –M), sodium hypochlorite (500mg/L) and benzalkonium chloride (0.02% volume/volume –v/v). The concentrations are based on review of the Page 121
Chapter 4 concentrations used in industry and comparable to those used in other work published in this area [113, 116, 134, 205-206]. Sodium hydroxide (molecular formula NaOH) is frequently referred to as caustic soda due to the highly caustic (corrosive) properties of the alkaline base (high pH). Sodium hydroxide is commonly used in the meat processing industry to clean carcasses, surfaces and equipment due to the ability of NaOH to break down lipids including animal fats and organic matter. Previously published research has indicated that Salmonella can survive low concentrations of sodium hydroxide [206]. McKee et al. isolated S. Typhimurium in a container with a solution of 1% sodium hydroxide (0.25M) used for scalding raw meat [206]. Salmonella survival in disinfectant solutions may also result in cross contamination onto food. Chorianopoulos et al. also demonstrated that S. enterica biofilm can survive after contact with a disinfectant product containing of sodium hydroxide [147]. The research presented by Chorianopoulos et al. indicated that solution of sodium hydroxide (1mM) only marginally reduced the number of viable cells (0.12-1.50 log 10 reduction) recovered from the S. enterica biofilm (established over 5 days) after contact for 60 and 180 minutes whereas the use of 100% hydrosol or essential oils and 80% ethanol resulted in a more significant reduction of cells recovered (>4 log 10 reduction) [147]. Sodium hypochlorite (molecular formula NaClO) is a membrane-active oxidising compound that permeates and destroys the bacterial cell wall proteins. Sodium hypochlorite is frequently used as a disinfectant agent for hard surfaces and blood spillages [129]. Park et al. compared the efficacy of 100ppm (100mg/L) aerosolized sodium hypochlorite and concentration of Page 122
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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
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
Page 98 and 99: Chapter 2 The results displayed in
Page 100 and 101: Chapter 2 Table 2.7: Difference bet
Page 102 and 103: Chapter 2 Table 2.8: The mean log 1
Page 104 and 105: Chapter 2 Figure 2.7: Graph of the
Page 106 and 107: Chapter 2 also used “high” soni
Page 108 and 109: Chapter 2 2.8. Summary All 13 strai
Page 110 and 111: Chapter 3 3. Abstract It has been e
Page 112 and 113: Chapter 3 classified as persistent
Page 114 and 115: Chapter 3 was plated onto TSA for e
Page 116 and 117: Chapter 3 Figure 3.1: The mean log
Page 118 and 119: Chapter 3 Figure 3.3: SEM image of
Page 120 and 121: Chapter 3 Table 3.2: Difference bet
Page 122 and 123: Chapter 3 3.4.3. Intra-serovar vari
Page 124 and 125: Chapter 3 3.4.4. Strain variation i
Page 126 and 127: Chapter 3 3.4.5. The density of bio
Page 128 and 129: Chapter 3 3.5. Discussion As illust
Page 130 and 131: Chapter 3 As discussed in section 3
Page 132 and 133: Chapter 3 increased biofilm appeare
Page 134 and 135: Chapter 4 Examining the efficacy of
Page 136 and 137: Chapter 4 through laboratory based
Page 138 and 139: Chapter 4 acid and quaternary ammon
Page 140 and 141: Chapter 4 the surface the temperatu
Page 144 and 145: Chapter 4 peracetic acid (100, 200,
Page 146 and 147: Chapter 4 As discussed previously,
Page 148 and 149: Chapter 4 Dey/Engley (Difco) neutra
Page 150 and 151: Chapter 4 sterilisation was achieve
Page 152 and 153: Chapter 4 IX. Aliquots of 100µl of
Page 154 and 155: Chapter 4 XV. XVI. XVII. XVIII. XIX
Page 156 and 157: Chapter 4 4.3. Results 4.3.1. Suspe
Page 158 and 159: Chapter 4 Table 4.3: Mean log 10 de
Page 160 and 161: Chapter 4 Benzalkonium chloride was
Page 162 and 163: Chapter 4 4.4. Discussion Suspensio
Page 164 and 165: Chapter 4 effective at eliminating
Page 166 and 167: Chapter 4 Surprisingly, Nguyen et a
Page 168 and 169: Chapter 4 though a contact time of
Page 170 and 171: Chapter 4 provide a more standardis
Page 172 and 173: Chapter 4 hours instead of the stan
Page 174 and 175: Chapter 5 5. Abstract Examining bio
Page 176 and 177: Chapter 5 dry and rough (bdar) morp
Page 178 and 179: Chapter 5 absence of curli and cell
Page 180 and 181: Chapter 5 studies such as the micro
Page 182 and 183: Chapter 5 discussed in chapter 4. T
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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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
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Bibliography Bibliography Page 221
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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
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Bibliography Supernatant of a Hafni
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Bibliography 165. Díez-García, M.
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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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Appendix 3 Appendix 3-Figure 2: PFG
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Appendix 4 Poster Presentation Envi
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