Isolation, characterization, and genome analysis of bacteriophage P929 that could specifically lyase the KL19 capsular type of Klebsiella pneumoniae.

In recent years, Klebsiella pneumoniae has caused an increase in the number of serious infections associated with pneumonia, septicemia, urinary tract infections, and pyogenic liver abscess. In this study, a phage P929, isolated from hospital sewage in Jiangsu, could specifically infect K. pneumoniae KL19 capsular type by forming plaques with a translucent halo that expanded over time. Phage P929 with a multiplicity of infection (MOI) of 0.1 produced the highest phage titer. According to a one-step growth curve experiment, the latent time period of phage P929 was 25 min, and the burst size was about 156 phage particles/cell. The sensitivity tests confirmed that P929 was stable at temperatures ranging from 4 to 50 °C and pH 3 to 11. Based on morphological observation and phylogenetic analysis, phage P929 could be assigned to a new species in the genus Drulisvirus of the subfamily Slopekvirinae in the family Autographiviridae. According to genome analysis, phage P929 was 44,764 bp in size with 53.66% G + C content, encoding 57 proteins or coding sequences (117-3699 bp in length). Phage P929 showed potential antibacterial activity on planktonic cells and biofilm. After 120 min, the OD600 values of five phage-treated groups were basically reached zero compared to the untreated group, and the antibacterial activity of P929 was still detectable within 390 min. In anti-biofilm tests, phage P929 at an MOI of 1 significantly reduced the biofilm formation of K. pneumoniae in 48 h. These results suggest that phage P929 may be used to treat carbapenem-resistant and biofilm-forming K. pneumonia in clinical settings.