effect of Streptomyces fradiae isolates against microbial pathogens (in vitro) and study its compatibility with biosynthesized zinc oxide nanoparticles

Background: Streptomyces comprises Gram-positive, filamentous, and sporeforming bacteria. Streptomyces fradiae has the capability to synthesize the antibiotics neomycin, tylosin, and fosfomycin. Aim: Detection of the inhibitory effect of S. fradiae isolates against microbial pathogens (in vitro) and study its compatibility with biosynthesized zinc oxide nanoparticles. Methodology: Fifty soil samples were gathered between December 2023 and January 2024. Specimens were gathered from several locations inside the city of Baghdad. Following the dilution of the sample, it was plated onto ISP2 agar to isolate Streptomyces. Multiple biochemical assays were conducted on the isolates. Zinc oxide nanoparticles were produced using Eucalyptus extract and evaluated against harmful microorganisms. Results: A total of 33 Streptomyces isolates were obtained, then identified as Streptomyces fradiae , 12 isolates did not exhibit any antibacterial effects against pathogenic bacteria. On the other hand, 21 isolates (63.6%) demonstrated strong antibacterial activity. Of the total isolates, 48.5% (16) exhibited antibacterial activity against both Escherichia coli (E. coli) and Staphylococcus aureus(Staph. aureus). However, only 15% (5 isolates) demonstrated activity, particularly against Staph. aureus. The zone of inhibition of the nanoparticles against the tested strains was 9mm, while for the Eucalyptus extract was 2.5mm against Staph. aureus. The inhibition zones against E. coli, on the other hand, were 11mm for nanoparticles and 3mm for the Eucalyptus extract. The effective concentration was 12.5% for the plant’s extract and 20% fornanoparticles. Conclusion: The Streptomyces’s bioactive molecule exhibited antibacterial properties. It was more effective against Gram-positive bacteria (Staph. aureus) than Gram-negative bacteria (E. coli). This study presents an environmentally friendly method for producing zinc oxide nanoparticles (ZnO NPs) using a leaf extract from Eucalyptus globulus as a reducing agent. The ZnNPs haveantibacterial efficacy against both E. coli and Staph. aureus. The antibiotic of Streptomyces was more effective than Zn NPs and Eucalyptus plants against pathogenic bacteria.