Bioprospecting and characterization of streptomyces species associated with termites in Kiang’odu section of mount Kenya forest for antimicrobial potential

Abstract

Antimicrobial resistance poses a major challenge to public health, necessitating the search for novel bioactive compounds from unexplored sources. This study aimed to characterize Streptomyces species from the gut of termites inhabiting mounds in a section of Mt. Kenya forest and evaluate their antibacterial activity against multidrugresistant pathogens: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter cloacae- ESKAPE. Twenty-five pure Streptomyces isolates were identified based on morphological and biochemical traits, including Gram positivity and spore type. Primary screening was done using the cross-streak method, and secondary screening using the agar well diffusion technique. Data on primary screening was analysed using ANOVA to assess differences among termites from various tree trunks. Secondary screening data, expressed as zones of inhibition (mm), underwent ANOVA with Bonferroni adjustments to compare isolates and pathogens. GC-MS–identified compound abundances per Streptomyces isolate were organized into a matrix (isolates × compounds), averaging duplicate entries. Hierarchical clustering using Euclidean distances and complete linkage quantified isolate similarities, visualized via dendrograms. All statistical and clustering analyses were conducted in R Studio version 4.2.2 at α = 0.05 using relevant packages. Results showed strongest antibacterial activity against S. aureus (e.g., isolates MTG-04 and MTG-09 with 14.00 mm inhibition zones, p < 0.0001), moderate activity against K. pneumoniae (MTG-11, 11.17 mm) and E. cloacae (MTG-04, 11.33 mm), and lower yet notable effects against A. baumannii (up to 9.33 mm) and P. aeruginosa (up to 10.83 mm). Secondary screening of crude extracts confirmed these trends, with isolate MTM-18 producing the largest zone against E. cloacae (15.00 mm, p < 0.05) and strong inhibition against K. pneumoniae (14.00 mm). GC-MS profiling identified a diverse range of bioactive metabolites, including fatty acid amides, triterpenoids, and esters, linked to antimicrobial and antioxidant activities. Streptomyces from termite guts in Kiang’ondu section of Mt. Kenya forest demonstrate promising antibacterial activity primarily against Grampositive bacteria, with select isolates (MTG-04, MTM18) identified as prime candidates for further characterization to optimize bioactive compound production and therapeutic potential.