Assessing the Antibacterial Effects of Alcoholic vs. Aqueous Extracts from <i>Chlorella vulgaris</i> on FimH and STX Gene Expression in Uropathogenic Bacteria

Abstract

Background: Urinary tract infections (UTIs) threaten the health of millions of people worldwide each year. The most important causative agents include Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, which contribute to infection through the expression of FimH and STX genes. Owing to increasing antibiotic resistance, researchers are investigating natural products as alternatives to antibiotic therapy. One such option is green algae, whose antimicrobial properties have been demonstrated in several studies. Objectives: In this study, the antimicrobial properties of alcoholic and aqueous extracts of Chlorella vulgaris were investigated. Methods: Aqueous and alcoholic extracts were prepared. Antibacterial activity, including disk diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC), was evaluated against ATCC reference strains of the three selected uropathogens. For qRT-PCR analysis of FimH and STX, clinical isolates derived from patients with UTIs (five per species) were used and compared with untreated ATCC reference strains. Results: Both extracts exhibited antibacterial activity against ATCC reference strains. Under the tested conditions, the alcoholic extract showed lower MIC/MBC values; however, the extracts were not normalized to specific bioactive compounds. The alcoholic extract also reduced the expression of FimH and STX in clinical isolates. Conclusions: These findings, based on ATCC reference strains for antimicrobial assays and clinical isolates for gene expression studies, indicate that C. vulgaris extract could serve as a natural approach for managing UTIs while contributing to reduced antibiotic resistance at the population level.