an investigation into the antibacterial activities of medicinal plants ...

4.4.3 Standard agar plate count technique
Calculation of the results in the microtitre plate assay indicated that the plant extract
might be stimulating the bacterial growth as values higher than 100% were obtained.
Colony counts of the controls and specific bacterial strains were compared to assess
if the bacterial strains with percentages of more than 100% were stimulated at the
specific plant extract concentration.
The standard agar plate count technique (Reynolds, 2004) was used to verify the
relative growth/inhibition percentages of the bacteria in specific microtitre plate
extract suspensions. The aim of this method was to visibly display the relative
growth/inhibition percentages of test bacteria in specific plant extracts in relation to
controls, by means of comparative colony counts.
After overnight incubation of microtitre plates, before the addition of INT, tenfold
serial dilutions were made from the microtitre plate bacterial suspensions.
The bacteria controls containing no plant extracts were also serially diluted to
determine the cfu/ml.
Aliquots (10 µl) of selected dilutions of the microtitre plate bacterial
suspensions were spread onto agar plates and incubated at 37 o C overnight.
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