Antioxidant and Antibacterial Activities of Secondary Metabolites Produced by Streptomyces Isolates Against Extended‐Spectrum β‐Lactamase‐Producing Bacteria

ABSTRACT Extended‐spectrum β‐lactamase (ESBL)–producing Gram‐negative bacteria pose a severe therapeutic challenge globally. Streptomyces remain one of the most prolific natural sources of antibacterial and antioxidant secondary metabolites, yet their activity against ESBL‐producing pathogens remains under‐explored. Soil‐derived Streptomyces isolates were screened for bioactivity, and the most potent strain (SM7) was identified by 16S rRNA sequencing. Secondary metabolites were extracted using ethyl‐acetate and evaluated for antibacterial activity against ESBL‐producing Escherichia coli , Klebsiella pneumoniae , and Enterobacter cloacae using agar diffusion, MIC, and MBC assays. Antioxidant activity was assessed using DPPH and ABTS assays, while GC–MS and molecular docking were employed to identify and characterize bioactive compounds. Streptomyces sp . SM7 exhibited strong antibacterial activity, producing inhibition zones of 21.4 ± 0.6 mm, 19.2 ± 0.4 mm, and 17.6 ± 0.5 mm against ESBL‐producing E. coli , K. pneumoniae , and E. cloacae , respectively. MIC values ranged from 62.5 to 250 µg/mL, with bactericidal MBC/MIC ratios of 2. The extract showed potent antioxidant activity with DPPH and ABTS IC₅₀ values of 48.9 µg/mL and 61.4 µg/mL, respectively. GC–MS identified 18 bioactive compounds, with 2,4‐di‐tert‐butylphenol (18.6%) as the major constituent, which exhibited a docking affinity of −7.1 kcal/mol against bacterial DHFR. Streptomyces sp . SM7 produces phenolic‐ and fatty‐acid‐rich metabolites with potent bactericidal and antioxidant activities against ESBL‐producing pathogens, highlighting its promise as a natural source of next‐generation antimicrobial agents. These findings support Streptomyces sp. SM7 as a promising lead for downstream purification, mechanism‐guided optimization, and future drug‐development efforts targeting difficult‐to‐treat ESBL‐producing Enterobacterales.