Isolation and phenotypic characterization of a lytic bacteriophage with quantitative host range and antibiofilm activity against clinical MRSA isolates.

Background: Methicillin-resistant Objectives: This study aimed to isolate and phenotypically characterize a bacteriophage active against clinical MRSA isolates and evaluate its replication kinetics, environmental stability, host range, and antibiofilm activity. Methods: Bacteriophages were isolated from hospital sewage by enrichment against all 51 confirmed MRSA isolates obtained from 207 clinical specimens, and a single isolate was selected based on highest plaque-forming titer, clear plaque morphology, and broadest lysis spectrum. Phage morphology was examined using transmission electron microscopy. Replication kinetics were assessed by one-step growth analysis, and stability was evaluated under varying pH and temperature conditions. Host range was determined using efficiency of plating (EOP) across four MRSA isolates representing the spectrum of qualitative susceptibility responses. Antibiofilm activity was assessed using crystal violet biomass assay and CFU-based viability analysis. Results: Among the 51 confirmed MRSA isolates, 98% (50/51) carried the Conclusions: The study provides comprehensive phenotypic characterization of an MRSA-targeting bacteriophage. Although whole-genome sequencing was not performed, the findings establish a functional baseline supporting future genomic and translational investigations.