Novel Klebsiella pneumoniae K23-Specific Bacteriophages From Different Families: Similarity of Depolymerases and Their Therapeutic Potential

Abstract

Antibiotic resistance is a major public health concern in many countries worldwide. The rapid spread of multidrug-resistant (MDR) bacteria is the main driving force for the development of novel non-antibiotic antimicrobials as a therapeutic alternative. Here, we isolated and characterized three virulent bacteriophages that specifically infect and lyse MDR <i>Klebsiella pneumoniae</i> with K23 capsule type. The phages belonged to the <i>Autographiviridae</i> (vB_KpnP_Dlv622) and <i>Myoviridae</i> (vB_KpnM_Seu621, KpS8) families and contained highly similar receptor-binding proteins (RBPs) with polysaccharide depolymerase enzymatic activity. Based on phylogenetic analysis, a similar pattern was also noted for five other groups of depolymerases, specific against capsule types K1, K30/K69, K57, K63, and KN2. The resulting recombinant depolymerases Dep622 (phage vB_KpnP_Dlv622) and DepS8 (phage KpS8) demonstrated narrow specificity against <i>K. pneumoniae</i> with capsule type K23 and were able to protect <i>Galleria mellonella</i> larvae in a model infection with a <i>K. pneumoniae</i> multidrug-resistant strain. These findings expand our knowledge of the diversity of phage depolymerases and provide further evidence that bacteriophages and phage polysaccharide depolymerases represent a promising tool for antimicrobial therapy.