Antibacterial Activity of Ethyl Acetate Extracts of Metabolites Produced by Endophytic Bacteria Isolated from Moringa oleifera Leaves against Antibiotic-Resistant Bacteria

Introduction: Endophytes are microorganisms colonizing healthy plants tissue without causing any apparent symptoms and noticeable injury to the host. They are reported as reservoir of various classes of broad spectrum bioactive compounds. Hence this study was conducted to evaluate the antibacterial activity of endophytic bacteria isolated from Moringa oleifera leaves against Methicillin Resistant Staphylococcus aureus and multidrug-resistant Escherichia coli.

Methods: Endophytic bacteria were isolated from healthy leaves of Moringa oleifera and were identified based on their cultural, microscopic and biochemical characteristics. The endophytic bacteria were screened for antibacterial against Methicillin Resistant Staphylococcus aureus and multidrug-resistant Escherichia coli. Ethyl acetate extracts of metabolites produced by endophytic bacteria with activities were evaluated for antibacterial activity against MRSA and MDR E. coli using agar well diffusion assay with dimethyl sulfoxide as control. The Minimum Inhibitory Concentration and Minimum Bactericidal Concentration of the ethyl acetate extracts were determined.

Results: Eleven endophytic bacteria were isolated from healthy leaves of Moringa oleifera. Four of the endophytes exhibited antibacterial activities against the test isolates. Ethyl acetate extracts of metabolites produced by endophytic bacteria showed a wide range of antibacterial activity with the inhibitory zone ranging from 11.0 to 27.0 mm for MRSA and 13.0 to 30.0 mm for MDR E. coli with MIC values between 50 mg/mL and 100 mg/mL. Dimethyl sulfoxide had no zone of inhibition against test isolates.

Conclusion: Ethyl acetate extracts of metabolites produced by endophytic bacteria isolated from leaves of Moringa oleifera exhibited antibacterial activity against antibiotic-resistant isolates and can serve as source of novel therapeutic agents.