Phenotypic characterisation of Klebsiella-specific phage and the study of antibiofilm activity and synergistic effect with meropenem on multidrug-resistant Klebsiella pneumoniae causing respiratory infections

Background: Klebsiella pneumoniae is a major pathogen that causes ventilator-associated pneumonia and can produce biofilms on endotracheal tubes. This can act as a diffusive barrier, hindering the treatment of infections caused by multidrug-resistant strains of the pathogen. Treatment of such multidrug-resistant strains has become a major challenge and a global problem. Among the various alternative methods used to combat this problem, the use of specific bacteriophages appears to be quite encouraging. This study aimed to isolate and perform phenotypic characterisation of Klebsiella-specific phage from sewage water and compare the effects of Klebsiella-specific phage and subinhibitory concentrations of meropenem on in vitro biofilm production by the respiratory clinical isolates of Klebsiella pneumoniae . Methods: Isolation and phenotypic characterisation of Klebsiella-specific phage from sewage water was done using K.pneumoniae subspp.pneumoniae ATCC 33495 as the host bacterium. The antibiofilm activity of the isolated phage was studied on 40 respiratory clinical isolates of Klebsiella pneumoniae . Their biofilm production was performed on endotracheal tubing pieces in microtiter plates as well as in the presence of Klebsiella-specific phage, subinhibitory concentrations of meropenem, and a combination of Klebsiella-specific phage and meropenem. Results: Transmission Electron Microscopy (TEM) confirmed a classic Myoviridae structure—an icosahedral head (50-100 nm) with a contractile tail sheath and a complex baseplate. Other characteristics included a latent period of 20 minutes and a burst size of 69 phage particles per cell, with a multiplicity of infection being 10, with strong host-killing ability and was stable and infective at 25 °C and a neutral pH range (6-7) Subinhibitory concentration of meropenem brought about a significant decrease in biofilm production (p<0.001) in 91.3% of meropenem-sensitive but significantly increased in 100% of meropenem-resistant strains. The combination of bacteriophage and meropenem had a synergistic effect, resulting in significant reduction in both the meropenem-sensitive and resistant strains Conclusion: This study suggests the potential application of specific phage-coated and antibiotic-coated endotracheal tubing in preventing biofilms, thereby reducing the risk of ventilator-associated pneumonia.