Experimental Protection of Mice against Lethal Staphylococcus aureus Infection by Novel Bacteriophage ϕMR11

The protective effects of bacteriophages were assessed against experimental Staphylococcus aureus infection in mice. Of the S. aureus phages isolated in the study, OMR11 was representatively used for all testing, because its host range was the most broad and it carries no genes for known toxins or antibiotic resistance. Intraperitoneal injections (8 X 10 8 cells) of S. aureus, including methicillin-resistant bacteria, caused bacteremia and eventual death in mice. In contrast, subsequent intraperitoneal administration of purified OMR11 (MOI ≥0,1) suppressed S. aureus-induced lethality. This lifesaving effect coincided with the rapid appearance of OMR11 in the circulation, which remained at substantial levels until the bacteria were eradicated. Inoculation with high-dose OMR11 alone produced no adverse effects attributable to the phage. These results uphold the efficacy of phage therapy against pernicious S. aureus infections in humans and suggest that OMR11 may be a potential prototype for gene-modified, advanced therapeutic S. aureus phages.