New Bacteriophages against Emerging Lineages ST23 and ST258 of and Efficacy Assessment in Larvae.

is a bacterial pathogen of high public health importance. Its polysaccharide capsule is highly variable but only a few capsular types are associated with emerging pathogenic sublineages. The aim of this work is to isolate and characterize new lytic bacteriophages and assess their potential to control infections by the ST23 and ST258 sublineages using a larvae model. Three selected bacteriophages, targeting lineages ST258 (bacteriophages vB_KpnP_KL106-ULIP47 and vB_KpnP_KL106-ULIP54) and ST23 (bacteriophage vB_KpnP_K1-ULIP33), display specificity for capsular types KL106 and K1, respectively. These podoviruses belong to the subfamily and their genomes are devoid of lysogeny or toxin-associated genes. In a larvae model, a mortality rate of 70% was observed upon infection by ST258 and ST23. This number was reduced to 20% upon treatment with bacteriophages at a multiplicity of infection of 10. This work increases the number of characterized bacteriophages infecting and provides information regarding genome sequence and efficacy during preclinical phage therapy against two prominent sublineages of this bacterial species.