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Chapter 4
Table 4.4: Mean log 10 density of viable 168 hour biofilm cells after contact with disinfectants (measured in Mean Log 10 CFU/coupon)
SL1344 SL483 S09-0494 S09-0717
Mean LR SD Mean LR SD Mean LR SD Mean LR SD
Disinfectant free Control N Time 9.74 0.04 9.78 0.04 9.74 0.03 9.68 0.01
Sodium Hydroxide 6 10 8.24 1.50 0.24 8.13 1.65 0.38 8.10 1.64 0.36 8.89 0.79 0.19
1 Mole 6 45 8.01 1.73 0.50 7.96 1.82 0.33 8.13 1.61 0.21 8.88 0.80 0.16
6 90 7.72 2.02 0.57 7.45 2.33 0.12 7.74 2.00 0.26 8.84 0.84 0.17
Sodium Hypochlorite 6 10 9.48 0.26 0.02 9.56 0.22 0.13 9.32 0.42 0.01 9.33 0.35 0.01
500mg/L 6 45 9.43 0.31 0.07 9.51 0.27 0.13 9.28 0.46 0.07 9.00 0.68 0.25
6 90 9.40 0.34 0.08 9.50 0.28 0.14 8.77 0.97 0.74 8.89 0.79 0.32
6 10 9.68 0.06 0.08 9.74 0.04 0.05 9.71 0.03 0.06 9.58 0.10 0.07
Benzalkonium Chloride 6 45 9.65 0.09 0.09 9.75 0.03 0.04 9.69 0.05 0.07 9.51 0.17 0.09
0.02%
6 90 9.64 0.10 0.09 9.47 0.31 0.24 9.65 0.09 0.12 9.49 0.19 0.09
Table 4.4: Presents mean log 10 density of cells recovered from concrete surfaces after contact with disinfectant agents. Strains examined
incorporated Salmonella enterica subspecies enterica serovar Typhimurium SL1344, Salmonella Agona SL483, S. Agona S09-0494 and Salmonella
Enteritidis S09-0717. After contact with 3 disinfectants for 10-, 45- and 90 minutes the viable cells were recovered and enumerated using the spread
plate technique on three replicate TSA plates. Each experiment was repeated twice. Table 4.2 presents the mean log 10 density (CFU/coupon) and the
standard deviation (SD) of all 6 counts. The log 10 reduction (LR) was calculated by subtracting mean log 10 density of cells from the test coupon from
the mean log 10 density of cells recovered from the control coupon i.e. control coupon – test coupon.
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