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 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
an 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.