Genomic characterization of a new phage BUCT541 against Klebsiella pneumoniae K1-ST23 and efficacy assessment in mouse and Galleria mellonella larvae

Over the past decades, the spread of multi-drug-resistant <i>Klebsiella pneumoniae</i> (MDR-KP) is becoming a new threat and new effective therapies against this pathogen are needed. Bacteriophage (phage) therapy is considered to be a promising alternative treatment for MDR-KP infections compared with antibacterial drug usage. Here, we reported a new phage BUCT541 which can lyse MDR-KP ST23. The genome of BUCT541 is a double-stranded linear 46,100-bp long DNA molecule with 48% GC content through the Next generation sequencing (NGS) data. A total of 81 open reading frames and no virulence or antimicrobial resistance genes are annotated in the BUCT541 genome. BUCT541 was able to lyse 7 of the 30 tested MDR-KP according to the host range analysis. And the seven sensitive strains belonged to the <i>K. pneumoniae</i> K1-ST23. BUCT541 exhibited high thermal stability (4-70°C) and broad pH tolerance (pH 3-11) in the stability test. The <i>in vivo</i> results showed that BUCT541 (4 × 10⁵ plaque-forming units (PFU)/each) significantly increased the survival rate of <i>K. pneumoniae</i> infected <i>Galleria mellonella</i> from 5.3% to 83.3% within 48 h. Moreover, in the mouse lung infection model, high doses of BUCT541 (2 × 10⁷ PFU/each) cured 100% of BALB/c mice that were infected with <i>K. pneumoniae</i>. After 30 h of treatment with phage BUCT541 of the multiplicity of infection (MOI) = 10, the <i>K. pneumoniae</i> in the lungs of mice was lower than 10⁴ CFU/mL, compared to the control group 10⁹ CFU/mL. Together, these findings indicate that phage BUCT541 holds great promise as an alternative therapy with excellent stability and a wide lysis range for the treatment of MDR-KP ST23 infection.