A novel K57-specific Klebsiella pneumoniae phage disinfects milk and inhibits biofilm formation

Klebsiella pneumoniae (K. pneumoniae) , especially serotype K57, is a major pathogen in dairy bovine mastitis , causing significant economic losses and posing a public health risk through contaminated dairy products . In addition, K57 is highly virulent among serotypes infecting humans, leading to serious conditions such as pyogenic liver abscess . In this study, we isolated and identified a bacteriophage called vB_Kp_Z57 that targets K57 serotype K. pneumoniae isolates from human and bovine sources. The phage has a latent period of 4 min and can produce approximately 233 phages per infected bacterial cell . vB_Kp_Z57 is stable over a temperature range of 4 °C to 60 °C and a pH range of 5–11. Sequencing and assembly of the phage genome revealed DNA molecules consisting of 40,316 base pairs. After genome annotation with bioinformatics software , it was discovered that the phage genome encodes 48 proteins, with no detected lysogeny genes, toxin genes, or tRNA-related genes. vB_Kp_Z57 was classified as a member of genus Przondovirus , family Autographiviridae. The results of bacteriostatic experiments show that vB_Kp_Z57 has a good effect on inhibiting bacterial growth. Notably, vB_Kp_Z57 significantly inhibited the growth of its host bacteria in milk at refrigerated temperatures of 4 °C and room temperature. Biofilm inhibition experiments revealed that phage vB_Kp_Z57 significantly reduced OD 595 values in all phage-treated groups, indicating its potential as an effective biocontrol agent against K. pneumoniae . Our findings show the promise of vB_Kp_Z57 as a novel and environmentally friendly solution to address the challenges associated with K. pneumoniae in dairy production. • A new phage lysing K57 serotype Klebsiella pneumoniae specifically was isolated and characterized. • The phage had significant antimicrobial properties in milk under cold storage and room temperature. • The phage significantly inhibited biofilm formation in both LB medium and milk. • The phage shows promise as a biological control agent for K. pneumoniae contamination in milk production.