Author: Okeke Chikaodili Eziamaka
Department: Botany
Affiliation: Nnamdi Azikiwe University Awka

The efficacy of three tropical plants for the inhibition of pathogens causing human diarrhoea was investigated. Ethanol was used as solvent for extraction.Six human pathogens; Escherichia coli, Bacillus subtilis, Salmnonella enterica, Pseudomonas aeruginosa, Staphylococcus citrinum and Aspergillus niger were employed in this study.The inhibitory effects of the ethanolic extracts of Psidium guajava L., Mangifera indica L. and Vernonia amygdalina L. on the test organisms were carried out using the agar well diffusion method of antimicrobial assay. Phytochemical screening of the plants was conducted. Antibiotic (Streptomycin) served as the control. Phytochemical (qualitative) screening of the plants revealed the presence of biologically active chemical compounds such as tannins, phenols, saponins, alkaloids, flavonoids and sterols. The quantitative determination of the phytochemicals revealed the different levels of concentrations.The minimum inhibitory concentration(MIC) of the extracts on the organisms ranged between 5.62-15.60mg/ml for Bacillus subtilis, 5.30-16.25mg/ml for Staphylococcus citrinum, 3.94-12.90mg/ml for Pseudomonas aeruginosa, 4.85- 13.75 for Escherichia coli, 4.50-12.36mg/ml for Salmonella enteric,5.40-14.10mg/ml for Aspergillus niger.The solvent used for extraction varied significantly(P<0.05) among the six test organisms. Staphylococcus citrinum and Bacillus subtilis were the most susceptible to the three extracts while Salmonella enterica was least inhibited. The significance of these findings was discussed in relation to the phytochemicals as a
means of disease control and the substitution of plant extracts as potential antimicrobial drug to the resistance of the human pathogens.

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