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Chapter 4
IX.
Aliquots of 100µl of the bacterial suspension (~1.5-5x10 7 CFU/ml)
were placed into each well of a 96 well microtitre plate using a
pipette.
X. Aliquots of 100µl of each disinfectant at the primary concentrations
were placed in each of the corresponding wells.
XI.
XII.
XIII.
XIV.
Therefore 100µl of 2000mg/L of sodium hypochlorite and 100 µl of
broth resulted in a working concentration of 1000mg/L of sodium
hypochlorite.
The plates were incubated for 24 hours at 37°C.
The plates were examined visually to assess turbidity after
incubation, with the presence of pellicle formation indicative of
bacterial growth.
Each disinfectant MIC test was performed in triplicate wells for each
strain and each test was performed on 2 different days.
4.2.2. Disinfectant testing method using the CBR
I. Twenty-four concrete coupons were used as a substratum for
biofilm growth in each biofilm reactor. A standard biofilm (48 hour
biofilm growth) was achieved by following the method described in
chapter 2 (Section 2.5.1) the older biofilm (7days- 168 hours) was
achieved as described in chapter 3 (Section 3.2).
II.
III.
IV.
After biofilm formation was complete the following method was
used.
Fresh solutions of disinfectants were used for each experiment.
Sodium hypochlorite (500mg/L), sodium hydroxide (1M) and
benzalkonium chloride (0.02%) were made using sterile H 2 0 and
filter sterilization.
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