Novel Bacteriophage Lysin with Broad Lytic Activity Protects against Mixed Infection by Streptococcus pyogenes and Methicillin-Resistant Staphylococcus aureus

Abstract

ABSTRACTMethicillin-resistantStaphylococcus aureus(MRSA) andStreptococcus pyogenes(group A streptococcus [GrAS]) cause serious and sometimes fatal human diseases. They are among the many Gram-positive pathogens for which resistance to leading antibiotics has emerged. As a result, alternative therapies need to be developed to combat these pathogens. We have identified a novel bacteriophage lysin (PlySs2), derived from aStreptococcus suisphage, with broad lytic activity against MRSA, vancomycin-intermediateS. aureus(VISA),Streptococcus suis,Listeria,Staphylococcus simulans,Staphylococcus epidermidis,Streptococcus equi,Streptococcus agalactiae(group B streptococcus [GBS]),S. pyogenes,Streptococcus sanguinis, group G streptococci (GGS), group E streptococci (GES), andStreptococcus pneumoniae. PlySs2 has an N-terminal cysteine-histidine aminopeptidase (CHAP) catalytic domain and a C-terminal SH3b binding domain. It is stable at 50°C for 30 min, 37°C for >24 h, 4°C for 15 days, and −80°C for >7 months; it maintained full activity after 10 freeze-thaw cycles. PlySs2 at 128 μg/mlin vitroreduced MRSA andS. pyogenesgrowth by 5 logs and 3 logs within 1 h, respectively, and exhibited a MIC of 16 μg/ml for MRSA. A single, 2-mg dose of PlySs2 protected 92% (22/24) of the mice in a bacteremia model of mixed MRSA andS. pyogenesinfection. Serially increasing exposure of MRSA andS. pyogenesto PlySs2 or mupirocin resulted in no observed resistance to PlySs2 and resistance to mupirocin. To date, no other lysin has shown such notable broad lytic activity, stability, and efficacy against multiple, leading, human bacterial pathogens; as such, PlySs2 has all the characteristics to be an effective therapeutic.