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Chapter 4
Table 4.3: Mean log 10 density of cells recovered from the 48 hour biofilm after contact with disinfectants (measured in Mean Log 10 CFU/coupon)
48 Hour biofilm –direct spread plate results
Disinfectant N Time Strain 1 - SL1344 Strain 2 - SL483
Mean LR SD Mean LR SD
Disinfectant free Control 7.63 0.02 7.66 0.01
Sodium Hydroxide
1 Mole
Sodium Hypochlorite
500mg/L
6 10 0 7.63 0 0 7.66 0
6 45 0 7.63 0 0 7.66 0
6 90 0 7.63 0 0 7.66 0
6 10 7.48 0.15 0.03 7.53 0.13 0.13
6 45 7.45 0.18 0.04 7.36 0.30 0.25
6 90 6.52 1.11 0.19 7.15 0.51 0.36
6 10 7.41 0.22 0.09 7.48 0.18 0.16
6 45 7.32 0.31 0.01 7.24 0.42 0.34
6 90 6.80 0.83 0.60 6.69 0.97 0.18
Benzalkonium Chloride
0.02%
Table 4.3: Presents mean log 10 density of viable cells recovered from Salmonella enterica serovar enterica subspecies Typhimurium SL1344 and S.
Agona SL483 biofilm attached to concrete coupons over 48 hours. 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 4.3 presents
the mean log 10 density (CFU/coupon) and the standard deviation 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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