Detection of Aquatic Streptomyces with Antimicrobial Effect on Gentamycin-resistant Escherichia coli in Bakhtegan Lake in Fars, Iran

Following the resistance of bacteria to antibiotics, the prevalence of antibiotic-resistant Escherichia coli (E. coli)strains has become a major medical challenge in recent years. It demands the development of effective antibiotics with natural origin. Actinomycetes are known for their ability to produce secondary metabolites and antibiotics. The aim of this study was to isolate aqueous Streptomyces species producing antimicrobial agents against gentamicin-resistant E. coli in Lake Bakhtegan in Fars province, Iran.

The first step was to obtain samples to evaluate the antagonistic effect of Streptomyces on antibiotic-resistant E. coli. In this study, 10 water samples were collected from Bakhtegan Lake. The bacteria were cultured in a specific culture medium (i.e., ISP2), and Streptomyces species were isolated and purified. The isolation and determination of the efficacy of secondary metabolites in the pathogens were performed by disk diffusion method. Deoxyribonucleic acid was extracted from effective Streptomyces for molecular analysis. The 16S ribosomal ribonucleic acid sequence was excised, and polymerase chain reaction was conducted using 27F and 1492R primers to identify the Streptomyces species.

In this study, 17 Streptomycin isolates were recovered from 10 water samples 7 of which secreted metabolites. In addition, one isolate with a more strong effect on gentamicin-resistant E. coli was sequenced and identified as Streptomyces species strain 11K402.

Based on the obtained results of this study, it can be concluded that aquatic environments are considered suitable sources for the detection and isolation of Actinomycetes and Streptomycetes with antimicrobial metabolites.