Antibacterial Activity of Ethyl Acetate Extracts of Endophytic Fungi Metabolites against Multidrug Resistant Staphylococcus aureus

Abstract

Endophytes are microorganism, typically bacteria or fungi that live within the tissues of healthy plants without causing harm to the host plant. Endophytes are recognized as an emerging source of therapeutic agents. This work was aimed at determining the antibacterial activity of ethyl acetate extracts of endophytic fungi metabolites against Multidrug Resistant Staphylococcus aureus. Ethyl acetate extracts of metabolite produced by endophytic fungi (Gonatobotrys sp. P21, Aspergillus sp. M12 and Aspergillus sp. V12) from previous work were used in this study. Isolates of Staphylococcus aureus were collected and confirmed based on their colonial morphology, Grams reaction and biochemical characteristics. Antibiotic susceptibility profile of the isolates was determined using disc diffusion method. Antibacterial activity of the ethyl acetate extracts of endophytic fungi metabolites was determined against the MDR S. aureus isolates using agar well diffusion method. Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentrations (MBC) of the extracts were also determined using tube dilution technique. The S. aureus isolates were resistant to more than three antibiotics, hence they were MDR isolates. The extracts exhibited antibacterial activity against the MDR S. aureus isolates with zones of inhibition ranging between 10.00 mm and 43.00 mm. Extract P21 had an MIC value of 100 µg/mL while extracts M12 and V12 were unable to inhibit the growth of MDR S. aureus at 100 µg/mL. Extract P21 was however found to be bacteriostatic at 100 µg/mL. Metabolites derived from the endophytic fungal isolates can serve promising source of novel compounds with therapeutic potentials.