No abstract

The aqueous ethanol and acetone-ethanolic extracts of Vernonia amygdalina leaves and stems were investigated for their antimicrobial activities compared to ciprofloxacin, against Escherichia coli, Klebsiella sp and Staphylococcus sp. The antimicrobial activity of each extract on the isolates was determined by agar well diffusion and minimum inhibitory concentration methods. The acetoneethanolic extract of the leaf showed the highest antibacterial activity on Klebsiella sp in both methods used, followed by the ethanol leaf extracts on the same organism. E. coli and Staphylococcus sp were not susceptible to any of the extracts even at higher concentrations. The aqueous extracts of both leaf and stem were ineffective on all the test isolates at all concentration. Comparatively, the test isolates were sensitive to ciprofloxacin in both methods used but the antibacterial effect of acetone-ethanolic leaf extract on Klebsiella sp was higher than that of ciprofloxacin on Klebsiella sp. The results from this research showed that V. amygdalina could be used as raw material in the synthesis of antimicrobial drugs, especially against Klebsiella sp which have been attributed with high level drug resistance in urinary tract infections.

Pathogenicity of biosurfactant-producing microorganisms is currently raising some health, safety and environmental concerns. As a result, the industrial-scale production and application of biosurfactants as potential alternatives to the synthetic one is still an unachieved task. The production of biosurfactants using nonpathogenic/recombinant strains requires more attention and investigation for some advantages that includes the discovery of non-toxic biosurfactants suitable for all industrial applications, identifying new biosurfactant congeners with better inherent surfaceactive properties compared to that from pathogens and synthetic ones and the synthesis of biosurfactant without complex metabolic regulations. Although a number of nonpathogenic/recombinant, eco-friendly biosurfactant-producing strains have been documented, there is need for more research in this area focusing especially on improved biosurfactant production by these strains using optimisation processes and the discovery of new nonpathogenic/recombinant strains using molecular techniques for future sustainability.