ABSTRACT
Due to the rapid increase in antibiotic resistance and the current unfavorable side effects of some available antibiotics, scientists have begun to seek alternate therapy in the treatment of various illnesses and diseases. Before the advent of modern medicine, treatment was dependent on the leaves, flowers and barks of plants. This has become the basis for recent research by screening plant extracts in order to discover new drugs and treatment options. Ocimum gratissimum is a medicinal plant widely known for its many traditional uses and bioactive properties. The purpose of this study was to analyze the antibacterial activity of O. gratissimum against diarrhea causing bacteria. The leaves of the plant were purchased, air-dried at room temperature, and then ground into powder using an electric blender. Ethanolic and aqueous extracts were obtained from the leaves and they were screened for the presence of phytochemicals as well as examined for the antibacterial activity of Ocimum gratissimum against Escherichia coli, Salmonella enterica, and Bacillus cereus. By reconstituting the extract in dimethyl sulphoxide (DMSO) to obtain different concentrations (0.2, 0.1, 0.05, and 0.025 g/ml) and using disc diffusion technique, the extracts were tested against the test organisms. Together, both extracts contained alkaloids, phlobatannins, flavonoids, glycosides, saponins, steroids, and tannins, according to the qualitative phytochemical examinations. Antibacterial testing revealed that the O. gratissimum extracts exhibited minimal antibacterial action against all three test organisms with zones of inhibition ranging from 6mm to 8mm. Bacillus cereus was the least susceptible bacterium being completely resistant to the aqueous extract of the leaves while Escherichia coli and Salmonella enterica were the most susceptible to the aqueous and ethanolic extracts respectively. The low susceptibility activity could be as a result of the growth conditions of the plant, the method of extraction adopted or a possible resistance factor occurring in the bacteria.
