Characterization of Methicillin-Resistant Staphylococcus aureus (MRSA) Phages From Sewage at a Tertiary Pediatric Hospital

Abstract

Background: The methicillin-resistant Staphylococcus aureus (MRSA) strain is now the most commonly reported antibiotic-resistant bacterium in clinical settings. Therefore, there is an urgent need to develop novel antibacterial agents to control this pathogen. Bacteriophages are a potential alternative treatment for MRSA infections. Objectives: The objective of this study was the isolation and characterization of MRSA phages from the sewage at a tertiary pediatric hospital. Methods: Two MRSA strains were isolated from patient blood. The isolated strains were confirmed as MRSA through the conventional methods. Phages were then isolated from the sewage at the tertiary pediatric hospital. Lytic activity was determined with a spot test, while the titers of phage lysates were measured using the DLA technique. The morphology was assessed using electron microscopy, and the latent period time and burst size were determined. Results: Electron microscopy showed MRSA phages’ resemblance to members of the family Siphoviridae, serogroups A and F. They exhibited a latent period of 70 minutes and a relatively burst size of 2,400 plaque-forming units (PFU)/infected cell. The titer of the phages was determined to be 3 × 109 PFU/mL using the by DLA technique. Conclusions: In this study, two phages from the family Siphoviridae were isolated and characterized from sewage at a tertiary pediatric hospital; these phages specifically target MRSA. Their presence may be one reason for the transfer of antibiotic resistance or virulence factors, resulting in transduction and the conversion of nonvirulent strains of Staphylococcus to virulent strains. Considering that phages through can be transferred to wards in an air-born manner, it is better to create negative pressure in the sewage pipes at hospitals until the phages can no longer transfer to the wards via aerosols.