Antibacterial activity of Honey, Bitter leaf and Garlic extracts on some Escherichia coli, Salmonella typhi and Shigella species

Honey and some selected plants extracts: garlic (Allium sativum) and bitter leaf (Vernonia amygdalina) were studied for their antimicrobial properties on selected human pathogenic bacteria of the family enterobacteriaceae namely Escherichia coli, Shigella and Salmonella. All the extracts exhibited various degrees of inhibition against the organisms at different concentrations. The minimum inhibitory concentration (MIC) measured in mg/mL on Escherichia coli, Salmonella typhi and Shigella species for the treatments were as follows: bitter leaf extract: 6.25±0.00, 12.50±0.00 and 6.25±0.00, garlic: 9.38±9.77, 12.50±0.00, and 6.25±0.00, and honey: 6.25±0.00, 9.375±9.77, and 6.25±0.00. The zones of inhibition measured in millimetres (mm) were as follows: bitter leaf extract: 19.0±1.00, 22.50±0.25, and 13.0±1.00, garlic extract: 21.0±0.00, 15.50±0.25 and 15.50±0.25 and honey: 34.0±1.00, 36.0±1.00 and 33.50±0.25. Garlic extract had a minimum bactericidal concentration of 12.50 mg/mL against Salmonella typhi, and 25.00 mg/mL on Shigella spp. Similarly, the minimum bactericidal concentration for honey was observed to be 25.00 mg/mL and 50.00 mg/mL against Salmonella typhi and Shigella spp. respectively while no minimum bactericidal concentration was observed for bitter leaf extract. While garlic extract had the least bactericidal concentration against Salmonella typhi, none of the extracts showed any bactericidal concentration against Escherichia coli. This means that among the three treatments garlic was the most effective antimicrobial agent against Salmonella typhi at a lower concentration.