Unraveling a new Klebsiella phage KP47 against Klebsiella spp.

BACKGROUND: The increase in cases of infectious diseases related to multidrug-resistant bacteria and the spread of multidrug-resistant genes have driven the search for therapeutic alternatives that can circumvent this global phenomenon. One of these alternatives is the use of bacteriophages, which are viruses capable of infecting and killing specific bacteria. Klebsiella pneumoniae species complex (KpSC) is an important opportunistic group associated with multidrug resistance. This group includes Klebsiella quasipneumoniae subsp. similipneumoniae, a species recognized as a clinically relevant pathogen, and that was used as a host (designated Klebsiella KH1) to isolate the phage characterized in the present study. The characterization of new phages is essential to expand the therapeutic arsenal and to improve our understanding on phage diversity. In this study, we evaluated a Klebsiella bacteriophage named KP47 that was isolated from sewage in the United Kingdom. We performed phage biological and genomic characterization in order to assess its therapeutic attributes. KP47 represents a newly isolated Klebsiella phage, being able to infect both K. pneumoniae and K. quasipneumoniae subsp. similipneumoniae, which also shows evidence of depolymerase activity and an efficient bacteriolytic performance.

RESULTS: The phage KP47 showed a typical morphology of the Caudoviricetes class, with a capsid of 48 nm and a tail of 161 nm. Its genome has 47,396 bp, 63 CDSs, and a GC content of 57.52%, which apparently encodes a depolymerase. ViPTree analysis placed KP47 near Drexlerviridae-related phages, while comparative analyses using representative RefSeq genomes revealed low intergenomic similarity. This phage demonstrated strictly lytic behavior and fast adsorption (90% in 6 min). MOI experiments indicated complete inhibition of bacterial growth in MOIs ≥ 1. The phage infected two out of nine tested strains belonging to the strains of KpSC.

CONCLUSIONS: In this study, we described the Klebsiella phage KP47, likely representing a new viral genus, that exhibits a strictly lytic lifestyle, rapid adsorption (90% within 6 min), and an effective bacterial growth inhibition at MOIs ≥ 1. KP47 was able to infect clinically relevant members of the Klebsiella pneumoniae species complex. Further investigations of its potential to act on biofilms and against Klebsiella species in in vivo models are of interest to evaluate its potential for clinical application.