Inhibition Of Microbial Biofilms
Microtitre plate assay (Removal)
In the removal of formed biofilms, it was found that earthworm extract was most effective at removing formed biofilms of E. coli and S. epidermidis, as shown in Figures 9 and 10, respectively. The absorbance of the sample was lower than that of the control without extract, suggesting that the biofilm has been partially dispersed in the presence of the extract.
Figure 9: The graph shows that only earthworm extract was effective in removing formed biofilm of E. coli.
Figure 10: The graph shows that only earthworm extract was effective in removing formed biofilm of S. epidermidis.
Note: The presence of lichen and cranberry extracts resulted in an unexpected higher absorbance compared to the control. This could be due to the components of the extracts binding to the biofilm, and producing a cross reaction with the crystal violet dye that resulted in a more intense colour and higher absorbance at 550 nanometre.
A repeat of the experiment was conducted to confirm the trend. It was again observed that earthworm extract was the most effective at removing formed biofilms of both bacteria. Additionally, mealworm extract also displayed slight ability in removing the biofilms. The results are shown in Figure 11.
Figure 11: A repeat of the experiment confirmed that both earthworm and mealworm extracts were effective in removing formed biofilms of E. coli and S. epidermidis.
After this, a similar microtitre plate assay test was conducted to see if the extract could disperse the established biofilm of P. fluorescens using two solvents, ethanol and saline. It was found that earthworm was the most effective at removing formed biofilm of P.fluorescens as well. This is shown in Figure 12.
Figure 12: The graph shows that only earthworm extract was effective in removing formed biofilm of P.fluorescens.
Hence, the percentage removal of established biofilm was calculated using the formula stated earlier and the results for each bacteria can be seen in Figure 13.
Figure 13: The graph shows that earthworm extract was the most effective in removing formed biofilm of the different bacteria.