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

previous studies with susceptibility testing of Proteus species (Stratchounski et al.,
1999) as well as Enterococcus & Streptococcus species (Andrews et al., 1999).
Screening was done for all the plant extracts at different concentrations against all
the bacterial strains. The final plant extract concentrations in the agar plates ranged
between 0.5 mg/ml and 20 mg/ml.
4.4.2.1 Agar plate preparation
The extraction procedure and the volume of the redissolving solvent (DMSO)
were adjusted to obtain a uniform stock solution concentration for each plant
extract.
Serial dilutions of the stock solution for each extract and traditional preparation
were made to a constant volume of 500 µl with sterile distilled water to
facilitate proper mixing of the extract and agar in the petri dishes.
The 500 µl plant extract dilutions were carefully mixed into approximately 20
ml diagnostic sensitivity test (DST) agar to obtain the final agar plate
concentrations ranging between 0.5 and 20 mg/ml.
Proper mixing of the extract with the sensitivity agar for a uniform extract
distribution was ensured and plates were allowed to set on a level dry surface.
Blood supplemented DST agar were used to facilitate the growth of E. feacalis
& S. pyogenes.
Supplementation of p-nitrophenyl glycerol (PNPG) to the diagnostic sensitivity
agar prevented the swarming of P. mirabilis on the test plates, improving the
reading of the plates for analysis (Figure 7).
Growth control plates were included for both Gram-positive and Gramnegative
test bacteria on BA plates and MacConkey agar (Biolab) plates,
respectively.
Agar plates supplemented with the redissolving solvent (DMSO) at a
percentage representative of the test extract plates were included as controls.
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