Nosocomial infections are a major challenge for public health due the high rates of morbidity and mortality generated. It was considered that the excessive or inappropriate use of antibiotics triggers the emergence of such resistant strains. Therefore, this situation obligated many researchers how to overcome this obstacle, mainly by searching or synthesizing new molecules to neutralize microbes and to overcome the phenomenon of resistance. Cyanobacteria characterized by their richness in some biologically active compounds, which was manifested such pharmaceutical importance. Hence, the present work has been focused on the study of the total phenolic component and the antibacterial activity of seven isolated filamentous Cyanobacterial species from freshwater of the river of Mekerra and waterfalls of El-Ourit (Sidi Bel Abbes and Tlemcen), located in North West region of Algeria. The extracted methanol and water of intracellular substances (from biomasses) and ethyl acetate of extracellular substances (from the culture supernatants) were screened for the estimation of total phenolic content by the using of Folin-Ciocalteu assay and investigated against different strains of Gram-positive such as Staphylococcus aureus and Gram-negative as Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonasaeruginosa) bacteria, where the tested strains were isolated from the patients suffered from a nosocomial pathogen bacteria. The obtained results indicated that solvents with different polarities have various effects on phenolic content. Furthermore, the obtained results indicated that among the tested solvents, the methanol extracts revealed the highest phenolic content. The study of the antagonistic activity of the isolated, selected seven Cyanobacteria indicated that the Methanolic extract of Anabaena sp revealed an excellent inhibition of Staphylococcus aureus. Furthermore, the ethyl acetate extracts of the isolated, selected seven Cyanobacteria was manifested an evident antagonistic activity against several pathogenic bacteria, with the absence of any effect on the growth of Pseudomonas aeruginosa. The pattern of inhibition in the bacterial bioassays indicated that various antibacterial substances are involved.