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

acterial strains. The microtitre plate assay using INT (p-iodonitrotetrazolium) as a
bacterial growth indicator gave reproducible results and allowed determination of the
MIC of each plant extract (Eloff, 1998a & Eloff, 1998b).
Initially the different plant extracts and traditional preparations were screened with the
bacterial strains in triplicate using the microtitre plate assay.
Certain bacteria, S. pyogenes, E. feacalis & P. mirabilis, were not compatible with the
microtitre plate assay using distilled water as the diluent and a microtitre plate reader
for analysis. Therefore an adapted agar dilution plate assay (Boswell et al., 2001;
Andrews, 2004) was used as an alternative method for determining the antibacterial
activity and MIC’s of the medicinal plant extracts with these bacteria.
The agar dilution plate assay incorporated the use of different dilutions of the plant
extract mixed into melted agar (Kerr et al., 1999; Andrews, 2004).
The equipment and techniques employed for investigating medicinal plant extracts
may play a role in the accuracy of reporting and comparing the results in different
studies. A schematic representation of the different steps performed in this study for
assessing the in vitro antibacterial activity of the selected medicinal plants is showed
in Figure 3.
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