Antimicrobial Activity of Some Plant Extracts and Their Interaction with Standard Antibiotics

Microbial infections pose significant challenges to healthcare globally, but the discovery of antimicrobial agents has revolutionized medicine and saved lives. Unfortunately, the misuse of antibiotics has led to antimicrobial resistance (AMR), a major global health concern. This study was designed to investigate the antimicrobial activities of the methanolic extracts of four medicinal plants and their interactions with some standard antibiotics against some normal and multidrug-resistant Gram-negative (fluoroquinolone-resistant Escherichia coli and Klebsiella pneumoniae ) and Gram-positive (methicillin-resistant Staphylococcus aureus ) bacteria strains, as well as fungi ( Candida albicans ). The extracts showed antimicrobial activities at varying concentrations, with the minimum inhibitory concentration (MIC) values ranging from 0.98 µg/ml to ≥ 500 µg/ml. The lowest MIC value (0.98 µg/ml) was recorded in Azadirachta indica and A. cissampeloides extract against E. coli ; these plant extracts also significantly reduced the MIC ciprofloxacin against of E. coli , thus, from 0.9 µg/ml to 0.12 µg/ml and 0.18 µg/ml representing 86% and 80% enhancement in activity respectively. The plant-antibiotic combination showed synergistic and additive effects against the tested microorganisms. This could enhance the efficacy of antibiotics and minimize the risk of antimicrobial resistance.