Characterizing a Lytic Bacteriophage Infecting Methicillin-Resistant Staphylococcus aureus (MRSA) Isolated From Burn Patients

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a significant threat to human health. It is a multidrug-resistant (MDR) pathogen capable of causing a variety of diseases. Also, MRSA is one of the most important nosocomial pathogens in burn infection. As a treatment strategy against MRSA infections, phage therapy has the potential of becoming an alternative remedy. Objectives: The present study aimed to isolate and characterize a lytic bacteriophage from hospital sewage to be effective against burn wound-infecting MRSA isolates. Methods: Staphylococcus aureus strains were isolated from hospitalized burn patients. The strains were confirmed as MRSA by the Kirby-Bauer disk diffusion method using penicillin, methicillin, and oxacillin, as well as the PCR assay for the mecA gene. The phage was isolated from the hospital sewage and tittered by the double layer agar (DLA) method. The spot test was used for host range determination. The latent period and burst size were estimated from a one-step growth curve. The phage morphology was observed by electron microscopy. The nature of the nucleic acid of the isolated bacteriophages was confirmed by Rnase A, Dnase I, and six restriction enzymes. Results: The titer, latent period, and burst size of the isolated phage were determined to be 1 × 109 PFU/mL, 20 min, and 190 PFU per infected cell, respectively. It displayed a broad host range for MRSA bacteria by the spot test (27 out of 30 isolates). Electron microscopy observation demonstrated that the phage belonged to the Myoviridea family. Digestion profiles of Rnase A, Dnase I, and six restriction enzymes in 1% agarose gel electrophoresis showed that the genome of the isolated phage was a double-stranded DNA with a size of < ∼23 kbp. Conclusions: The isolated phage (MH-1) was active against a wide range of MRSA strains recovered from burn patients. Its specificity and remarkable lytic effects on MRSA strains emphasized that it could be a suitable candidate for use in prophylaxis and treatment of these clinical infections.