Isolation and in Vitro Characterization of Specific Bacteriophages against Methicillin-Resistant Staphylococcus aureus

Backgrounds: Bacteriophage therapy could be an alternative strategy for the treatment of antibiotic-resistant bacteria. This study aimed to evaluate the antibacterial activities of isolated bacteriophages against methicillin-resistant Staphylococcus aureus (MRSA) isolates.  Materials Methods: A total of 16 clinical isolates of MRSA were collected from medical diagnostic laboratories in Tehran, Iran. A specific bacteriophage was isolated from hospital sewage using double-layer agar. Phage morphology was evaluated by transmission electron microscopy (TEM). Different bacteria were selected to determine the bacteriophage host range using spot test. Phage susceptibility to temperature and pH was evaluated by double-layer agar method.  In vitro assay was carried out on human epithelial type 2 (HEp-2) cells to investigate the effect of bacteriophage on the adhesion of MRSA to human epithelial cells.  Findings: TEM suggested the Myoviridae family for the isolated phage. The effective titer of bacteriophages was 1.8×107 PFU/mL. The isolated bacteriophage was stable at 4 ˚C and pH=8. The isolated bacteriophage was specific for all clinical isolates of MRSA and had no lytic activity against other pathogenic bacteria. In evaluating the binding and invasion of MRSA to the HEp-2 cell line, as expected, the lytic activity of specific bacteriophages was observed following inoculation. Conclusion: The specificity and lytic activity of this phage on MRSA and MRSA-infected HEp-2 cell line emphasized that the isolated bacteriophage may serve as an effective prophylactic and alternative therapeutic agent in hospital settings.