In-Vitro and In-Vivo Antibacterial Activities of Croton macrostachyus Methanol Extract against E. coli and S. aureus

An experimental trial was conducted to investigate the In-vitro and In-vivo antibacterial activity of Croton macrostachyus leaf extracts against Escherichia coli and Staphylococcus aureus. Antimicrobial susceptibility test using disc diffusion and broth micro-dilution test for the determination of minimum inhibitory concentration (MIC) were used to assess the antibacterial activity of methanolic extracts from the plant. Commercial antibiotic disc (tetracycline) was used as positive reference to determine the sensitivity of the bacterial strains. Seventy two (72) albino mice weighted between 35-45g were used for In-Vivo bacterial inhibitory activity of the plant extract. The mice were allotted in six (6) groups of twelve (12) animals. Clinical signs, body weight changes and post-mortem findings were registered during the study period. Phytochemical screening of Cr. macrostachyus leaf methanol crude extract showed presence of terpenoids, alkaloids, phenolic compounds, saponin, tannins and flavonoids. Methanol extract of Cr. macrostachyus showed a strong effect in inhibiting growth of tested isolates in In-Vitro and In-Vivo. Extracts from Cr. macrostachyus plant showed stronger antibacterial activity against S. aureus than E. coli with minimum inhibitory concentration values of 3.75mg/ml and 7.5mg/ml, respectively. The extract has shown the lowest inhibition zone (9.25±0.54mm) against E. coli and the highest inhibition zone (21.63±0.02) was seen against S. aureus. In addition, the extract was significantly better than the effect of tetracycline against S. aureus (P<0.05)). Relatively higher number of organs with lesion and death of mice during the trial was registered in experimental groups, infected with E. coli than S. aureus infected ones, both treated with the plant extract. These findings present scientific evidences for the use of this plant as a remedy against disease caused by S. aureus and E. coli pathogens. Finally, recommendations were made for further investigation to be done for evaluating its particular therapeutic dose and optimize their application in patients.