Antimicrobial Activity of Vernonia amygdalina, Ocimum gratissimum and Gongronema latifolium Synergy on Common Foodborne Pathogenic Bacteria

The search for antimicrobial agents from natural sources such as diverse plant species against foodborne pathogens has less side effect than chemically synthesized compounds. In this study, antimicrobial activity of ethanolic extract, hot and cold aqueous extracts of Vernonia amygdalina, Ocimum gratissimum and Gongronema latifolium was tested against Escherichia coli, Staphylococcus aureus and Listeria monocytogenes. The leaf extracts of Vernonia amygdalina did not show antimicrobial activity against the test isolates. The diameter of zone of inhibition shown by ethanolic leaf extract of Gongronema latifolium and Ocimum gratissimum against S. aureus is 12.0±1 mm and 10±2 mm, respectively. With regards to ethanolic leaf extract of Gongronema latifolium and Ocimum gratissimum, the diameter of zone of inhibition demonstrated against L. monocytogenes and E. coli is 18.0±2 mm and 6.0±1 mm, respectively. A synergistic ethanolic or aqueous extracts of the leaves did not show antimicrobial activity against the test isolates. However, ethanolic extracts of Gongronema latifolium and Ocimum gratissimum used separately is an effective antimicrobial agent the test isolates.