Abstract The increasing resistance of Staphylococcus aureus highlights the urgent need for new antibacterial alternatives. In this context, Streptomyces, a genus of actinobacteria widely recognized for its biosynthetic potential, represents a promising source of bioactive compounds. This study evaluated the antibacterial activity of a crude ethyl acetate extract obtained from the culture supernatant of Streptomyces albus against S. aureus strains. The extract was produced by submerged fermentation followed by liquid–liquid extraction with ethyl acetate. Antibacterial activity was assessed using the agar diffusion method, as well as by determining the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). Two clinical strains (IC 3792 and IC 2141) and one reference strain (ATCC 29213) were evaluated. The extract produced inhibition zones ranging from 18.00 ± 1.0 mm to 22.33 ± 0.58 mm. MIC and MBC analyses demonstrated both inhibitory and bactericidal activity. Notably, strain IC 2141 exhibited an MIC of 625 µg/mL and a corresponding MBC, resulting in an MBC/MIC ratio ≤ 2, indicative of a bactericidal effect. These findings demonstrate that the crude extract obtained from S. albus exhibits antibacterial activity, including against strains with reduced susceptibility to conventional antibiotics. Overall, soil-derived actinobacteria represent a promising source of bioactive compounds, reinforcing the relevance of microbial bioprospecting in the development of new therapeutic strategies to address increasing bacterial resistance.
G. S. Souza, F. David, W. R. S. Gomes et al.· Brazilian Journal of Biology· 0 citations
The increasing failure of antimicrobial therapies against Pseudomonas aeruginosa represents a major challenge in clinical practice, particularly in patients with chronic lung disease and critical illness. Beyond intrinsic and acquired resistance, biofilm formation and persister cell populations contribute to persistent and refractory infections, limiting the efficacy of conventional antibiotics. Lacticaseibacillus rhamnosus has emerged as a source of bioactive compounds capable of interfering with multiple stages of P. aeruginosa pathogenesis. Its antimicrobial activity involves organic acid production, secretion of low-molecular-weight metabolites, enzymatic effects, and biosurfactant-mediated disruption of adhesion and biofilm formation. In addition, interactions with host epithelial cells indicate a role in modulating inflammatory responses and enhancing mucosal defenses. Cell-free supernatant (CFS) retain many of these properties and may represent a safer alternative to live probiotic administration. Despite consistent experimental evidence, key limitations remain, including variability in strain selection, lack of standardization of cell-free preparations, and incomplete characterization of active compounds. Clinical studies suggest potential benefits in reducing colonization and ventilator-associated pneumonia, although robust evidence is still limited. These findings support the potential role of L. rhamnosus as an adjunctive strategy in the management of P. aeruginosa infections, while highlighting the need for mechanistic standardization and clinical validation.
W. R. S. Gomes, Gessiane Dos Santos Souza, João Inácio Diniz Ferreira et al.· Folia Microbiologica (Prague...· 0 citations
