Characterization Of Lytic Bacteriophage Specific To Staphylococcus Aureus: A Step Towards Phage Therapy

Abstract

The rising incidence of antibiotic-resistant Staphylococcus aureus infections, including methicillin-resistant strains (MRSA), has intensified the demand for alternative antimicrobial strategies. This study focuses on the isolation and characterization of lytic bacteriophages specific to S. aureus to assess their potential application in phage therapy. Phages were isolated from sewage and hospital wastewater, purified through plaque assays, and subjected to morphological and molecular characterization. The phages demonstrated notable resilience across a broad pH spectrum (4.0–10.0), with optimal infectivity observed between pH 6.0 and 8.0. A decline in lytic activity was noted at extreme acidic and alkaline values, indicating potential for application in physiological environments. Heat resistance assays showed that phages retained significant activity up to 45°C, with gradual reduction in infectivity observed at higher temperatures. No viable activity was detected beyond 60°C, indicating their suitability for application and storage at ambient and body temperatures. Long-term viability testing revealed that the phages maintained over 80% infectivity when stored at 4°C for up to six months. Lyophilized samples preserved at 20°C demonstrated superior stability, suggesting freeze-drying as an effective method for formulation. The phages exhibited a broad host range, lysing a diverse panel of S. aureus clinical isolates, including multi-drug resistant strains. Specificity tests confirmed negligible activity against non-target Gram-positive and Gram-negative species, affirming their safety and selectivity. In vitro bacterial reduction assays revealed rapid bactericidal action within the first 2 hours post-phage application, achieving 99% reduction of viable bacterial counts. These results underscore the therapeutic potential of the phages in controlling S. aureus infections. Collectively, the characterized phages demonstrate strong lytic activity, stability under diverse conditions, and a broad host range, reinforcing their promise as effective agents in phage therapy against S. aureus.

 Keywords: S. aureus, antibiotic-resistant, lytic bacteriophages