Antimicrobial combination effect of Allicin, Lycopene and Quercetin on antibiotic-resistant bacteria

Document Type : Original Article


1 Department of Microbiology and Biotechnology, Caleb University Lagos, Nigeria.

2 Department of Microbiology, Edo State University Iyamho, Edo State, Nigeria


Background: The application of phytochemicals to treating microbial infections in humans globally is increasing with potent activity in combination. Aim: The study evaluated the antimicrobial combination effect of allicin, lycopene, and quercetin extracted from garlic, tomatoes, and onions respectively against methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE) and multi-drug resistant (MDR) Escherichia coli. Methods: Six antibiotic-resistant isolates: three clinical isolates and three American isolates were tested. Antimicrobial combination effect of the extracted phytochemicals was evaluated using the agar well diffusion method at varied concentrations and incubation periods. Results: At 50 µg, quercetin inhibited MDR  Escherichia coli and MRSA alone with mean zones of 15±0.95 mm – 49±3.09 mm whereas lycopene inhibited MRSE with the highest mean zone of 19±1.20 mm. Combination activity of allicin: lycopene: quercetin was best at 2:3:2 µg at both 24 h and 48 h with mean zone 20±1.26 mm – 44±2.77 mm and at 5:1 µg concentration for lycopene: quercetin with mean zone 16±1.01 mm - 25±1.58 mm for all test bacteria. On the typed culture isolates, the inhibition mean zones were 8±0.50 mm – 20±1.27 mm and 8±0.50 mm – 22±1.39 mm for singly and in combination, respectively. There was a significant (p < 0.05) combination activity of the phytochemicals on the test bacteria at 24 h and 48 h. Conclusion: To our knowledge, this is the first report of the antimicrobial combination activity study of allicin, lycopene, and quercetin. Our findings suggest further combination evaluations of phytochemicals for effectively controlling antibiotic-resistant infections.


Main Subjects