Aim: A novel endophyte, Streptomyces kebangsaanensis was isolated from the stem of a Malaysian ethnomedicinal plant, Portulaca oleracea in 2013. Studies on S. kebangsaanensis crude extract showed that it had antifungal activities and further work led to isolation of a novel compound, phenazine-1-carboxylic acid (PCA). This study investigated the combinatorial effect of PCA isolated from S. kebangsaanensis with amphotericin B on the growth of four clinical Fusarium solani isolates. Methodology and results: Disk diffusion assay showed that the crude extract of S. kebangsaaneesis inhibited growth of all four F. solani isolates. Whereas, the compound PCA from this extract inhibited two of the tested F. solani isolates, UZ541/12, and UZ667/13 at minimum inhibitory concentration of 18.00 µg/mL Combinations of this compound with amphotericin B, reduced the minimum inhibitory concentration of amphotericin B for these two isolates from 8 to 0.13 µg/mL and 4 to 0.03 µg/mL respectively. Analysis of fractional inhibitory concentration index showed that a borderline synergism is present between the compound and amphotericin B. Conclusion, significance and impact of the study These results indicate PCA may be useful in improving actions of available drugs against antimicrobial resistant microorganisms.
Streptomyces