Preliminary screening on the antimicrobial effects of Streptomyces extracts against Burkholderia pseudomallei from Sarawak

Abstract

Melioidosis is a potentially life-threatening infectious disease caused by the Gram-negative bacterium, Burkholderia pseudomallei. This preliminary study evaluates the antimicrobial potential of nineteen (19) pre-selected Streptomyces crude extracts, sourced from the Sarawak Biodiversity Centre Microbial Natural Product Library, against 29 B. pseudomallei strains isolated from Sarawak. Antimicrobial activity was assessed using the spot-on-lawn assay, and inhibition zone diameters were measured to quantify extract potency. Extracts E11, E12 and E15 exhibited broad and high inhibitory activity against 24 (82.76%) of the tested B. pseudomallei strains, followed by E6, E8, E9 and E18, which inhibited 23 (79.31%) strains. Extract E4 produced the largest inhibition zones, measuring 26 mm against strain MSHR 6824, and 25 mm against five additional strains (SWK-C 411, SWK-C 412, SWK-C 415, SWK-C 410 and SWK-C 417). Notably, four of the 29 strains exhibited complete resistance, with no measurable inhibition zones for any of the extracts tested. These preliminary findings highlight the potential of Streptomyces extracts as promising antimicrobial candidates against B.pseudomallei. Extracts demonstrating strong inhibitory activity will be subjected to liquid phase MIC/MBC assays to determine antimicrobial potency and to distinguish bacteriostatic from bactericidal effects.