Characterization of Bacteriophages Infecting Klebsiella pneumoniae Clinical Isolates in Ibadan: A Preliminary Investigation

Klebsiella pneumoniae is an opportunistic pathogen responsible for severe nosocomial infections, including pneumonia, bloodstream infections, and neonatal sepsis, with carbapenem-resistant strains posing a critical therapeutic challenge. Bacteriophage therapy is being revisited as a potential adjunct to antibiotic treatment, making the characterization of K. pneumoniae-specific phages clinically relevant. This study performed preliminary characterization of bacteriophages infecting clinical K. pneumoniae isolates obtained from patients at the University College Hospital (UCH), Ibadan, Oyo State. Sewage effluent samples were used as phage sources. Phage isolation was performed by double-agar overlay assay, and host range was determined against a panel of 25 K. pneumoniae isolates including carbapenem-resistant (CRKP) strains. Phage DNA was extracted and subjected to restriction enzyme fingerprinting and partial tail fiber gene sequencing for phylogenetic classification. Three lytic phages with distinct plaque morphologies were isolated. All three demonstrated lytic activity against CRKP strains, with one phage achieving a broad host range against 68% of the panel. Sequence analysis classified two phages within the Myoviridae family. These preliminary findings support further investigation of phage therapy applications for CRKP infections in Southwest Nigerian hospitals. Keywords: bacteriophage, Klebsiella pneumoniae, carbapenem resistance, phage therapy, Ibadan.