Antibacterial ability of bioactive compounds produced by <i>Saccharothrix algeriensis</i> DSM 44581 against multidrug-resistant uropathogenic bacteria

The overuse of antibiotics in treating urinary tract infections (UTIs) has led to increased bacterial resistance, complicating UTI management. <i>Actinomycetota</i> (previously known as <i>Actinobacteria</i>), are a prolific source of bioactive compounds with therapeutic potential. <i>Saccharothrix algeriensis</i> DSM 44581, a bacterium isolated from Algerian Saharan soil, produces various dithiolopyrrolone antibiotics depending on the composition of its culture medium. This study aimed to evaluate its antibacterial activity against multidrug−resistant uropathogenic bacteria. The antibacterial activity of <i>S. algeriensis</i> was assessed in a semi-synthetic fermentation broth under three conditions: semi-synthetic medium (SSM) without adding precursors, SSM supplemented with sorbic acid, and SSM added with cystine. Fifty uropathogenic strains were used as target bacteria, including forty strains from the family <i>Enterobacteriaceae</i> and ten strains of <i>Staphylococcus saprophyticus</i>, all with diverse antibiotic resistance profiles. Inhibition diameters varied with culture conditions: 0-40.33 mm in SSM without precursors, 0-39 mm in SSM with sorbic acid, and 0-35 mm in SSM with cystine. Furthermore, two specific antibiotics produced by <i>S. algeriensis</i>, thiolutin and 2-hexonyl-pyrrothine, were purified using high-performance liquid chromatography (HPLC), and their Minimum Inhibitory Concentrations (MICs) were determined against the uropathogenic strains. These antibiotics exhibited moderate to high activity against <i>Staphylococcus saprophyticus</i>, with MICs ≤75 μg/mL. In contrast, they showed low to no activity against <i>Enterobacteriaceae</i>, with MICs exceeding 150 μg/ mL. These findings suggest that <i>S. algeriensis</i> could be a promising source of antibiotics efficient against <i>Staphylococcus saprophyticus</i>.