Detection of antibiotic-producing microorganisms with antimicrobial activities against selected clinical isolates

Soil microorganisms, particularly from diverse environments, are known for producing bioactive compounds with potential applications in combating antibiotic-resistant pathogens. This study investigated the antimicrobial activities of secondary metabolites produced by microorganisms isolated from various soil samples sites within Ahmadu Bello University, Zaria-Nigeria. Potential antibiotic-producing microorganisms were isolated and screened for antibiotic production using crowded plate and dual-culture methods respectively. The isolated microorganisms were identified using phenotypic characterization. Secondary metabolites of the isolated microorganisms were tested for antimicrobial activities against some clinical isolates (Staphylococcus aureus, Escherichia coli, Candida albicans and Malassezia furfur) using agar well diffusion method. The antibiotic-producing microorganisms with antagonistic activities against these clinical isolates were phenotypically identified to be Bacillus amyloliquefaciens, Rhodotorula mucilaginosa, Candida tropicalis, Mucor circinelloides, and Penicillium chrysogenum. The secondary metabolites of these soil microorganisms exhibited varying degrees of inhibitory activities at different concentrations (12.5-100%) against the clinical isolates. Different concentrations of Candida tropicalis metabolite (12.5-100%) showed broad spectrum activities against the clinical isolates with diameter zones of inhibition ranging from 15-50 mm. This study showed the potential of the isolated soil microorganisms in developing new antimicrobial agents to address the growing challenge of antimicrobial resistance.