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Chapter 5
XIII.
XIV.
XV.
XVI.
XVII.
The difference in optical density was calculated by subtracting the
optical density of the control wells from the optical density of the
test wells.
Optical density (OD 590 ) was measured using the Dynex Technologies
model-Best 2000 and the data was accumulated using Revelation
Software version 5.19.
The experiments were repeated on three different days.
The data was analysed using SPSS version 20 using the same
statistical tests as described in chapter 1 (mean, standard deviation
and comparisons of data using Mann-Whitney U test for nonparametric
data).
The strains were examined in three wells in each experiment and
each experiment was performed on 3 different days. Therefore the
mean and standard deviation were calculated on 9 optical density
measurements (observations).
5.2.3. Disinfectant testing
I. The test strains were streaked onto LB and XLD plates and
incubated at 37°C for 24 hours as previously.
II.
III.
IV.
The three disinfectants as detailed in chapter 4 were used in this
chapter sodium hypochlorite (500mg/L), sodium hydroxide (1 Mole
–M), and benzalkonium chloride (0.02%).
The disinfectants were made using sterile H 2 0 and filter sterilized
compounds, which were made on each day of experimentation.
A bacterial suspension was made to an optical density of 0.2 in
sterile saline using a hand held OD reader.
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