Wide Host Range and Strong Lytic Activity of Staphylococcus aureus Lytic Phage Stau2

Abstract

ABSTRACT In searching for an alternative antibacterial agent against multidrug-resistant Staphylococcus aureus , we have isolated and characterized a lytic staphylophage, Stau2. It possesses a double-stranded DNA genome estimated to be about 134.5 kb and a morphology resembling that of members of the family Myoviridae . With an estimated latency period of 25 min and a burst size of 100 PFU/infected cell, propagation of Stau2 in liquid culture gave a lysate of ca. 6 × 10 10 PFU/ml. It was stable at pH 5 to 13 in normal saline at room temperature for at least 4 weeks and at −85°C for more than 2 years, while 1 × 10 9 out of 2 × 10 12 PFU/ml retained infectivity after 36 months at 4°C. Stau2 could lyse 80% of the S . aureus isolates (164/205) obtained from hospitals in Taiwan, with complete lysis of most of the isolates tested within 3 h; however, it was an S . aureus -specific phage because no lytic infection could be found in the coagulase-negative staphylococci tested. Its host range among S . aureus isolates was wider than that of polyvalent phage K (47%), which can also lyse many other staphylococcal species. Experiments with mice demonstrated that Stau2 could provide 100% protection from lethal infection when a multiplicity of infection of 10 was administered immediately after a challenge with S . aureus S23. Considering these results, Stau2 could be considered at least as a candidate for topical phage therapy or an additive in the food industry.