Antimicrobial Activity of Endophytic Fungi Isolated from Leaf of Coriandrum Sativum

Abstract

The evolution and spread of resistance among pathogenic microbes to different antibiotics currently in use is a global health problem. Attempts are being made to tackle this major health issue by involving policy makers, scientists, healthcare professionals, the general public and industry. Several strategies have been suggested to retard the evolution of drug resistance. Major strategies used include improvement of prescribing practices, use of combination therapies and synthetic antibiotics, and development of species-specific antibiotics. However, most of the new antibiotic molecules which are being prepared to be marketed are only modifications of existing ones, thus lacking novelty in their mechanism of action or target sites. It is reasonable to expect that the introduction of totally new antibiotics would delay the evolution of drug resistance. Diverse group of endophytic fungi exist within every plant tissue which constitute major and novel natural therapeutic compounds. In this context, the current study was undertaken to investigate the antimicrobial action of endophytic fungi Aspergillus sojae isolated from the leaf of Coriandrum sativum. The endophytic fungus was isolated from the leaf of Coriandrum sativum and was identified from its macroscopic and microscopic features. To confirm the identity of fungal isolate, 18S sequencing was done. Disc diffusion method was used for antibacterial activities. The extract was used against Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Klebsiella pneumoniae and Escherichia coli. The tested bacteria included both gram positive and gram negative species. For antifungal activities the extract was tested against Aspergillus flavus and Fusarium oxysporum. Among the tested bacterial species the extract was highly effective against Pseudomonas aeruginosa (15 mm in size) at 100 mg/ml concentration. Moderate activities were also observed against Escherichia coli (13.5 mm) and Klebsiella pneumoniae (12.5 mm) at 100 mg/ml concentration of the endophytic extract. The extract had low activity (8.5 mm inhibition zone) at 100 mg/ml against Staphylococcus aureus but no activity against Salmonella typhi (5.0 mm inhibition zone). Here 5.0 mm is equal to the size of empty well. The extract had no effect (inhibitory zones were 5.5 mm at 50 mg/ml and 6.0 mm at 75 and 100 mg/ml respectively) against the tested fungi (Aspergillus flavus and Fusarium oxysporum). Of the 5 concentrations (12.5, 25.0, 50.0, 75.0 and 100 mg/ml) used for MIC determination, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus showed growth on 12.5, 25.0, 50.0 mg/ml but inhibited at 75.0 mg/ml. The lowest MIC recorded was 50.0 mg/ml for Escherichia coli. Growth of Salmonella typhi was not inhibited with any of the five used concentrations (12.5, 25.0, 50.0, 75.0 and 100 mg/ml). None of the used concentrations could inhibit the growth of the tested organisms Aspergillus flavus and Fusarium oxysporum. This study concludes that endophytic fungi (Aspergillus sojae) isolated from the leaf of Coriandrum sativum has the potential to produce bioactive metabolites active against many gram negative bacteria and may be used in pharmaceutical industry. The generated data has provided the basis for its application in the pharmaceutical industry in the form of traditional and folk medicine.