Antibacterial Activity of Ocimum gratissimum Leaf Extract Against Pathogenic Enterobacteriaceae

Medicinal plants have bioactive constituents that are used for treating and healing various human ailments. This study aimed to investigate the antibacterial potentials of Ocimum gratissimum leaves against some pathogenic members of Enterobacteriaceae. Fresh leaves of Ocimum gratissimum were collected from a farm in Unguwan Rimi, Kaduna State, Nigeria. The leaves were thoroughly washed, shade-dried at room temperature, and ground into a fine powder. Ethanolic and methanolic extracts were obtained via cold maceration. The phytochemical screening was carried out and the antibacterial activity was determined using agar well diffusion at different concentrations. The result of phytochemical analysis revealed the presence of phenol, tannins, saponins, cardiac glycosides and steroids for both ethanolic and methanolic extracts. The ethanolic extract of Ocimum gratissimum exhibited antibacterial activity against Escherichia coli, with a mean zone of inhibition ranging from 20.8 ± 4.71 mm to 13.8 ± 1.84 mm, while the methanolic extract showed a range of 21.6 ± 4.90 mm to 15.2 ± 1.97 mm. Against Klebsiella spp., the ethanolic extract produced inhibition zones ranging from 25.5 ± 4.40 mm to 18.2 ± 1.50 mm, whereas the methanolic extract showed a more variable range from 20.5 ± 5.00 mm to 6.00 ± 0.00 mm. For Pseudomonas aeruginosa, the zone of inhibition for the ethanolic extract varied from 19.5 ± 2.76 mm to 14.2 ± 1.70 mm, while the methanolic extract ranged from 21.0 ± 7.00 mm to 14.5 ± 5.00 mm. The minimum inhibitory concentration (MIC) of the ethanolic extract against E coli was 250 mg/mL, while that of the methanolic extract was 125 mg/mL. The minimum bactericidal concentration (MBC) for both extracts was 250 mg/mL. For Klebsiella spp., the MIC values were 500 mg/mL for the ethanolic extract and 250 mg/mL for the methanolic extract. Corresponding MBC values were 500 mg/mL (ethanolic) and 250 mg/mL (methanolic). In the case of Pseudomonas aeruginosa, the MICs were 500 mg/mL for the ethanolic extract and 250 mg/mL for the methanolic extract, and MBC followed the same pattern. The result suggests that O. gratissimum could be considered as a good antibacterial agent and can be used as an alternative cure to infections caused by these pathogens. Future studies should explore its therapeutic potential and safety profile.