The Antimicrobial Effects of Secondary Metabolites of Anguillan Fungi

Introduction: Many drugs have been isolated from fungal species. This study aims at identifying fungal species isolated in Anguilla in order to determine the antimicrobial effect of their secondary metabolites from pure culture against Staphylococcus aureus by demonstrating the presence of a zone of inhibition in the culture plate.

Methods: Samples were cultured and sub-cultured to isolate pure culture on potato dextrose yeast agar (PDYA) and chosen for further studies by the presence of surface exudates. Those cultures that produced copious amounts of surface exudates were examined for antimicrobial effects by further testing.

Results: Antimicrobial testing of MB0725C (P. digitatum) samples did not result in any evidence of antimicrobial properties. However, MB0725A (P. chrysogenum) punch biopsy-agar overlay produced a 11 mm ZOI, whereas crude exudates testing resulted in a 27 mm ZOI. Crude culture filtrate of potato dextrose broth (PDB) did not result in any ZOI for either MB0725A or C. Sensitivity testing on samples collected from Yeast Extract Lactose Broth (YELB) on Day 3, Day 6, Day 9 and Day 12 resulted in ZOI of 11 mm, 13, 15 and 17 mm respectively. The change in pH for MB0725A liquid culture in PDB versus YELB was significantly different (N=12, P<0.0001).

Conclusion: MB0725A was an excellent producer of surface exudates and further experiments showed that its secondary metabolites had antimicrobial effects against Staphylococcus aureus using Kirby-Bauer sensitivity testing.