Isolation and Genomic Characterisation of Five Novel Lytic Bacteriophages Infecting the Emerging Pathogen Klebsiella grimontii.

Klebsiella grimontii is an emerging pathogen associated with multidrug resistance. Although a single recent study reported phages against K. grimontii, their taxonomic diversity and structural characterisation remained limited. Here, we describe the isolation and characterisation of five novel lytic bacteriophages that specifically target K. grimontii strain K15g, originally isolated from a rotting iris rhizome. Phages Silvester, Lyra, Lyris, Mirion, and Helios were isolated from wastewater samples collected in the Moscow region and represent three distinct morphotypes: podovirus (Silvester), siphovirus (Lyra, Lyris, Mirion), and myovirus (Helios). Whole-genome sequencing revealed that Silvester belongs to the genus Przondovirus (family Autographiviridae); Lyra, Lyris, and Mirion are members of the genus Sugarlandvirus (family Demerecviridae); and Helios falls within the genus Slopekvirus (family Straboviridae). All five phages lack genes associated with lysogeny, virulence factors, or antibiotic resistance, indicating their suitability for therapeutic applications. Structural modelling of the receptor-binding proteins revealed diverse architectures of adsorption apparatuses, including a two-depolymerase complex in Silvester, T5-like tail fibres in the Sugarlandvirus phages, and a set of long and short fibres with a structured cell-puncturing device in Helios. This study presents five novel phages active against Klebsiella grimontii and provides a basis for further evaluation of their potential in phage therapy.