Due to increased antibiotic resistance, it is necessary to source for new antimicrobial substances that will help curb antimicrobial resistance. The aim of this research was to evaluate the antibacterial activity of Ocimum basilicum in-vitro on some enteric pathogens. The phytochemicals present in the aqueous and ethanol extracts were analyzed using standard methods which reveal the presences of alkaloids, glycosides, saponins, phenols, flavonoids, tannins, proteins and carbohydrates. Three (3) clinical isolates of Escherichia coli, Salmonella typhi, and Shigella flexneri were used in this study. Wells of 4 mm were bored on inoculated plates of solidified Muller Hinton Agar containing the test organisms. The antimicrobial activity of the aqueous and ethanol extracts were analyzed on the test organisms using standard method at varying concentrations of 200 mg/ml, 100 mg/ml, 50 mg/ml, 25 mg/ml and12.5 mg/ml, minimum inhibitory concentration was carried out using the broth dilution assay and the minimum bactericidal concentration was carried out by streaking method. Ciprofloxacin was used as a positive control. From the result the zones of inhibition ranged from 11mm to 5mm, in which Escherichia coli had zones of inhibition ranging from 11 mm-6 mm, Salmonella typhi had zones of inhibition of 8 mm-6 mm while Shigella flexneri had zones of 11 mm-7 mm. Escherichia coli and Shigella flexneri showed the highest zones of inhibition of 11 mm at 200 mg/ml compared to Salmonella typhi with a zone of inhibition of 9 mm at 200 mg/ml. This study revealed that the ethanol extract showed more antibacterial activity compared with the aqueous extract which had no activity on the test organisms. The minimum inhibitory concentration of the ethanol extract was at the concentration of 200 mg/ml for all the test organisms. The minimum bactericidal concentration at 200 mg/ml revealed the presences of growth on the plates for all the test organisms. Therefore the minimum bactericidal concentration of the extract against the test organisms will be at a concentration >200 mg/ml. The findings from this research revealed that Ocimum basilicum has the capability for treating diarrhea. Further research and purification of the plant extract both in-vivo and in-vitro assay is necessary.
