Isolation of four lytic phages infecting Klebsiella pneumoniae K22 clinical isolates from Spain

This article belongs to the Special Issue Bacteriophage—Molecular Studies.The emergence of multi-drug-resistant bacteria represents a major public-health threat. Phages constitute a promising alternative to chemical antibiotics due to their high host specificity, abundance in nature, and evolvability. However, phage host specificity means that highly diverse bacterial species are particularly difficult to target for phage therapy. This is the case of Klebsiella pneumoniae, which presents a hypervariable extracellular matrix capsule exhibiting dozens of variants. Here, we report four novel phages infecting K. pneumoniae capsular type K22 which were isolated from environmental samples in Valencia, Spain. Full genome sequencing showed that these phages belong to the Podoviridae family and encode putative depolymerases that allow digestion of specific K22 K. pneumoniae capsules. Our results confirm the capsular type-specificity of K. pneumoniae phages, as indicated by their narrow infectivity in a panel of K. pneumoniae clinical isolates. Nonetheless, this work represents a step forward in the characterization of phage diversity, which may culminate in the future use of large panels of phages for typing and/or for combating multi-drug-resistant K. pneumoniae.This research was funded by ERC Consolidator Grant 724519 Vis-à-vis, project PROMETEO2016-122 from Generalitat Valenciana, and project BFU2017-89594R from MICINN. B.B was funded by a PhD fellowship from Spanish MCIU FPU16/02139.Peer reviewe