Characterization of novel<i>Staphylococcus aureus</i>lytic phage and defining their combinatorial virulence using the OmniLog® system

Abstract

Skin and soft tissue infections (SSTI) caused by methicillin resistant <i>Staphylococcus aureus</i> (MRSA) are difficult to treat. Bacteriophage (phage) represent a potential alternate treatment for antibiotic resistant bacterial infections. In this study, 7 novel phage with broad lytic activity for <i>S. aureus</i> were isolated and identified. Screening of a diverse collection of 170 clinical isolates by efficiency of plating (EOP) assays shows that the novel phage are virulent and effectively prevent growth of 70-91% of MRSA and methicillin sensitive <i>S. aureus</i> (MSSA) isolates. Phage K, which was previously identified as having lytic activity on <i>S. aureus</i> was tested on the <i>S. aureus</i> collection and shown to prevent growth of 82% of the isolates. These novel phage group were examined by electron microscopy, the results of which indicate that the phage belong to the <i>Myoviridae</i> family of viruses. The novel phage group requires β-N-acetyl glucosamine (GlcNac) moieties on cell wall teichoic acids for infection. The phage were distinct from, but closely related to, phage K as characterized by restriction endonuclease analysis. Furthermore, growth rate analysis via OmniLog® microplate assay indicates that a combination of phage K, with phage SA0420ᶲ1, SA0456ᶲ1 or SA0482ᶲ1 have a synergistic phage-mediated lytic effect on MRSA and suppress formation of phage resistance. These results indicate that a broad spectrum lytic phage mixture can suppress the emergence of resistant bacterial populations and hence have great potential for combating <i>S. aureus</i> wound infections.