Student Projects/Antibacterial activity

ANTIBACTERIAL ACTIVITY

Phytochemical Analysis and Assessment of Antibacterial Potential of Entada gigas (L.) and Combretum indicum (L.)

Determination of Minimum Inhibitory Concentrations (MIC’s) of the effective plant extracts:

MIC is defined as the lowest concentration of the antimicrobial agent that inhibits the microbial growth after 24 hours of incubation to assess the antimicrobial susceptibility of extracts. The MIC was determined by micro broth dilution method using 96-well plates to evaluate the extract efficiency in inhibiting bacterial growth. Different concentration of plant extract were prepared ranging from 5 mg/ml to 0.009 mg/ml. 100 µl of Nutrient broth was poured into sterile 96-well plates and seeded with 50 µl of Salmonella typhi bacterial inoculum of the pathogenic strains. The plates were incubated at 37°C for 24 hours, followed by the matching of bacterial turbidity equivalent to 0.5 McFarland,and recorded against the concentrations of effective plant extract. The wells were then serially diluted by transferring 100 µl from the first well to the next until the tenth well. 100 µl was discarded from tenth well. Positive control wells were similarly treated. Positive control well contained 1 mg/ml Gentamicin. Negative control well had no sample. After the incubation, visual observation of growth was based on the colour change after adding the TTC dye shows red colour by the growth of microorganism. The concentration of the well containing the lowest sample concentration that prevented visible growth or change in colour was considered the MIC.

Minimum Inhibitory Concentrations of the effective plant extracts:

The MIC of the active extracts of Entada gigas were employed by microbroth dilution method to evaluate the minimum quantity of extract required to inhibit bacteria. The Chloroform and Ethyl acetate extract concentration ranged from 5 mg/ml to 0.009 mg/ml. It was observed that minimum quantity of plant extract required to inhibit the test organisms was 0.009 mg/ml for both Chloroform and Ethyl acetate extract. The MIC of the positive control was 0.009 mg/ml. Growth control was used as sterility control to know the broth was contamination free. Negative control of the solvent did not have any effect on the growth of the bacteria Salmonella typhi.