Synergistic Antibacterial Activity of Selected Plant Extracts in Combination with Antibiotics: An In Vitro Study
Keywords:
Azadirachta indica, neem, synergy, antibiotics, antibacterial activity, Escherichia coli, Staphylococcus aureus, in vitro studyAbstract
Background: The rising prevalence of antibiotic-resistant bacterial strains has become a major global health concern, necessitating the exploration of alternative and adjunct antimicrobial strategies. Medicinal plants, particularly Azadirachta indica (neem), are widely recognized for their broad-spectrum antimicrobial properties and potential to enhance the activity of conventional antibiotics.
Aim: The present study aimed to evaluate the synergistic antibacterial activity of aqueous extract of Azadirachta indica (neem) in combination with selected antibiotics (ampicillin and ciprofloxacin) against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 under in vitro conditions.
Materials and Methods: This in vitro experimental study was conducted in the Microbiology Laboratory of Annor Dental College. Fresh neem leaves, authenticated by a botanist, were collected locally and aqueous extract was prepared using standard procedures. Reference strains of E. coli ATCC 25922 and S. aureus ATCC 25923 were procured from HiMedia Laboratories. Antibacterial activity was assessed using the agar disc diffusion method on Mueller-Hinton agar. Zones of inhibition were measured for neem extract, antibiotics, and their combinations. All experiments were performed in triplicate.
Results: The aqueous neem extract demonstrated moderate antibacterial activity against both test organisms. Ciprofloxacin exhibited higher antibacterial activity compared to ampicillin. However, combinations of neem extract with both antibiotics showed significantly enhanced zones of inhibition compared to individual agents. The most pronounced synergistic effect was observed with neem–ciprofloxacin combination against both E. coli ATCC 25922 and S. aureus ATCC 25923.
Conclusion: The study demonstrates that aqueous extract of Azadirachta indica exhibits significant synergistic antibacterial activity when combined with conventional antibiotics. These findings suggest that neem may serve as a potential adjuvant to enhance antibiotic efficacy and may contribute to strategies aimed at combating antibiotic resistance.
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