PHENOTYPIC CHARACTERIZATION OF FIVE PHAGES ACTIVE AGAINST ANTIBIOTIC-RESISTANT KLEBSIELLA PNEUMONIAE.

Widespread antibiotic resistance represents an increasingly significant burden for healthcare systems worldwide. One of the primary contributors to this pressing issue is Klebsiella pneumoniae, a pathogen of major clinical concern. Here we describe five distinct phages that infect antibiotic-resistant K. pneumoniae strains. A total of 100 clinical bacterial strains were systematically assessed for their antibiotic- and phage susceptibility profiles. Notably, 94 of these strains demonstrated high levels of antibiotic resistance across multiple drug classes. The five described phages, which target nearly all studied strains, were comprehensively characterized regarding their virion morphology, their lytic spectra, their intracellular growth parameters, and their potential to trigger development of phage-resistant bacterial forms. Two Siphoviridae phages exhibited remarkably low rates of phage-resistant form development during the study period. While such rates were comparatively higher for the three Myoviruses tested, bacterial forms that acquired resistance to these particular phages subsequently became sensitive to other phages in the collection. In conclusion, the studied phages effectively targeted 93 out of 100 bacterial strains tested. Such broad coverage of diverse clinical strains by these phages strongly underscores their considerable potential in therapeutic settings, particularly for treating multidrug-resistant infections.