ABCD-type phage cocktail targeting distinct LPS receptor sites demonstrates superior efficacy against...

The narrow host range of phages poses a limitation in addressing multidrug-resistant bacteria, whereas phage cocktail therapy, targeting multiple bacterial receptors, broadens the phage host spectrum. This study establishes a comprehensive Salmonella phages repository through nationwide surveillance in China, isolating 242 phages classified into 29 genera, with genome sizes ranging from 5.4 to 350.3 Kb. Based on LPS specificity, phages were categorized into four types A-D. Here, we developed an ABCD-Type phage cocktail targeting four distinct LPS recognition sites, demonstrating superior efficacy versus single phages or phage cocktail with different receptors (CCR-Type). In vitro, ABCD-Type phage cocktail treatment sustained bactericidal activity > 36 h versus CCR's 8 h, effectively controlling Salmonella in lettuce, milk, and Galleria mellonella infection models. Moreover, ABCD-Type phage cocktail effectively cleared Salmonella biofilms and showed promising results in the treatment of animal infections, significantly reducing bacterial loads in infected chicks and improving their survival rates. Resistant mutants predominantly harbored mutations in the btuB gene and LPS biosynthesis genes. These mutants showed increased antibiotic sensitivity and attenuated virulence. Collectively, these findings underscore the therapeutic potential of Salmonella phages, specifically ABCD-Type phage cocktail formulations which contain the phages PJNS014, PJNS023, PJNS036, and PJNS038, for controlling Salmonella infections. This work provides a foundation for developing advanced phage-based therapeutics.