Effective of phage cocktail against Klebsiella pneumoniae infection of murine mammary glands

Phage therapy has potential to combat antibiotic-resistant bacteria causing bovine mastitis. Our objective was to use 3 Klebsiella lytic phages to create a phage cocktail, and to compare bactericidal activity of this phage cocktail versus an individual phage, both in vitro and in vivo. Based on transmission electron microscopy, phage CM_Kpn_HB154724 belonged to Podoviridae and on double agar plates, it formed translucent plaques on the bacterial lawn of Klebsiella pneumoniae KPHB154724. In one-step growth curves, this phage had a latent period of 40 min, an outbreak period of 40 min, a burst size of 1.2 × 107 PFU/mL, and an optimal multiplicity of infection (MOI) of 1. Furthermore, it was inactivated under extreme conditions (pH ≤ 3.0 or ≥ 12.0 and temperatures of 60 or 70 °C). It had a host range of 90% and had 146 predicted genes (Illumine NovaSeq). Based on histopathology and expression of inflammatory factors interleukin-1β, tumor necrosis factor-α, interleukin-6, and prostaglandin, phage cocktail therapy had better efficiency than an individual phage in K. pneumoniae-infected murine mammary glands. In conclusion, we used 3 Klebsiella lytic phages to create a phage cocktail and confirmed its effectiveness against K. pneumoniae both in vitro (bacterial lawn) and in vivo (infected murine mammary glands).