Evaluating the antibacterial activity and safety of bioactive compounds extracted from a brackish water Streptomyces cavourensis strain BA1

Abstract

<title>Abstract</title> Antibiotic-resistant microorganisms pose a significant danger to civilization, particularly due to the lack of current effective antibiotics. This work included the isolation and identification of <italic>Streptomyces cavourensis</italic> strain BA1 (PX588109) by morphological and molecular characterization. The filtrate of the <italic>S. cavourensis</italic> strain BA1 showed significant antibacterial efficacy against two multidrug-resistant pathogens, <italic>Escherichia coli</italic> and <italic>Klebsiella pneumoniae</italic> . The ethyl acetate organic phase had the greatest inhibitory efficacy among the solvent extracts. GC-MS spectra revealed the presence of several potent antibacterial compounds: 9,12-Octadecadiens (Z,Z) TMS-derivate, Palmitins TMS-derivate, Linoleates trimethylsilyl ester, and Methyl-10,12-heptadecadienoleate. The cytotoxicity assessment prove that the oil toxins produced by ethyl acetate extracts are considered moderately safe for the kidney of African Green Monkey (VERO cell line), with CC50 values of 296.1 µg/ml. The findings demonstrate that <italic>S. cavourensis</italic> strain BA1 extracts had a positive safety profile, hence augmenting their potential for medicinal applications. The SEM images of <italic>E. coli</italic> cells treated with the filtrate of <italic>S. cavourensis</italic> strain BA1 exhibited irregularities, with some surface cells appearing dented, wrinkled, or fractured. The treated <italic>K. pneumoniae</italic> cells exhibited notable elongation in comparison to the control cells. Other cells exhibited pronounced creases and curvatures, with some cellular debris indicating potential leakage of cellular contents due to membrane rupture. These results underscore the significant bactericidal potential of fatty acids when combined with naturally occurring antimicrobial agents and facilitate future investigation of <italic>S. cavourensis</italic> strain BA1 as a unique ideal source of bioactive chemicals to address antibiotic resistance.