The novel prophage lysin Lys1459 exhibits broad-spectrum antibacterial activity via triple-binding domain

Phage-encoded lysins represent a promising class of antimicrobial agents against drug-resistant bacteria due to their ability to degrade bacterial cell walls. This study characterizes a novel prophage-derived lysin, Lys1459, from Streptococcus uberis . We expressed and purified the full-length Lys1459 protein, along with its three individual domains (CHAP, A2, and CBD), to systematically evaluate its antibacterial spectrum, biochemical properties, and therapeutic efficacy. The full-length Lys1459 demonstrated potent lytic activity, achieving a 3-log reduction in Streptococcus agalactiae H-11-1 within 30 min at 50 μg/mL in Tris-HCl buffer. Notably, the three functional domains exhibited distinct binding spectra, which collectively contributed to a broad lytic range against streptococcal pathogens, including S. agalactiae, S. dysgalactiae, S. uberis , and S. pyogenes . In a mouse bacteremia model, intraperitoneal injection of Lys1459 significantly protected mice from lethal infection by S. agalactiae sgcDS001. Furthermore, the bacterial count of S. agalactiae in the blood of the treated mice was reduced by nearly three orders of magnitude. Our findings identify Lys1459 as a triple-binding-domain lysin with broad-spectrum bactericidal activity and robust in vivo efficacy, highlighting its potential as a therapeutic alternative against S. agalactiae infections. IMPORTANCE A three-domain lysin, Lys1459, was identified in Streptococcus uberis SX-5-2. The differential binding specificities of the CHAP, A2, and CBD domains to bacterial cells likely underlie the enzyme’s broad-spectrum lytic activity against various Streptococcus species, including S. agalactiae , S. dysgalactiae , S. uberis , and S. pyogenes. A significant protective effect against lethal S. agalactiae infection was observed in mice treated intraperitoneally with Lys1459.