Isolation and Identification of a Siphoviridae Bacteriophage Targeting Multidrug-resistant Klebsiella pneumoniae

Based on the WHO, multidrug-resistant Klebsiella pneumoniae is a priority pathogen that causes opportunistic infections and is widely spread in the environment. Phage therapy is considered a natural, safe, and very efficient alternative to treat difficult-to-treat infections.

This study aimed to isolate highly virulent, lytic bacteriophages and evaluate their efficacy for lysing multidrug-resistant K. pneumoniae.

Municipal wastewater samples were collected and filtered using 0.22 µm syringe filters and cultivated with log-phase cultures of K. pneumoniae using enrichment media. After 48 h of incubation, the cultures were centrifuged, and the resultant supernatant was filtered (0.22 µm). The detection of the phage was done using the spot assay with K. pneumoniae as the host. One-step growth kinetics and bacterial reduction tests were conducted to assess the growth kinetics of the isolated phage. The stability of the isolated phage was characterized by subjecting it to various temperature and pH conditions. The chemical stability of the K. pneumoniae phage was determined by exposing it to various organic compounds. A panel of 20 bacterial strains was tested using the spot assay, as well as double agar overlying assay, to determine the host range of the isolated phage.

Out of 40 wastewater samples tested, only one sample was tested positive for the K. pneumoniae phage (2.5%) that was lytic against the host strain. The K. pneumoniae phage had a latent period of 15 min and a burst size of 100 virions per infected cell. It was most stable at 37°C and pH range of 6.0 to 10.0. Chemically, the K. pneumoniae phage was resistant to 10% chloroform treatment. Transmission electron micrograph indicated that the K. pneumoniae phage belonged to the order Caudovirales, family Siphoviridae, morphotype B1.

Most of the characteristic features of the K. pneumoniae phage indicated the potential of this phage to be used in phage therapy. Hence, a comprehensive study is highly recommended to characterize the K. pneumoniae phage genome, detect its molecular interactions with the host cell, and determine its lytic activity in combination with other phages, which may lead to the efficient utilization of this phage in phage therapy against K. pneumoniae infections.