Phenotypic Determination of Phage Susceptibility among Multidrug-Resistant Bacteria Isolated from Clinical Samples of Patients of Tertiary Care Centre, Nepal

Shrestha S, Yadav P, Khadka P, Sah R, Mishra SK, Rai JR and Sharma S

Published on: 2023-09-21



The global challenge posed by the emergence of multidrug-resistant (MDR) bacterial species has heightened interest in alternate medicinal approaches. For almost a century, bacterial illnesses have been explored using bacteriophages (BPs) as therapeutic agents. Without harming mammalian cells, the lytic BPs have the ability to lyse bacteria. Because BPs use unique modes of action to provide antibacterial activity, it is believed that they are much safer and better tolerated.


We aimed to isolate and evaluate the in vitro efficacy of BPs against MDR bacteria and establish an alternative strategy to antibacterial therapy.

Materials and Methods

BPs were isolated from different environmental sources: river sites, ponds, and sewage. The presence of phages was determined by the Double Layer Agar Assay. Concentrations of phages were determined in plaque-forming units per milliliter (PFU/mL) by performing a plaque assay, and a susceptibility test was done by observing their lytic effect on pre-identified MDR bacteria.


BPs were obtained from 11 different sources, and 52 out of 73 BPs that showed clear lytic properties were selected. The majority of the isolated phages had lytic effects on their respective specific MDR bacteria to varying degrees, mostly with high efficacy (+++) and high specificity. However, minimum lytic effect even on Citrobacter freundii, indicating a narrow spectrum.  had a wider spectrum of lytic effects on the majority of the MDR isolates. Overall, phages specific for Gram Negative Bacilli (GNB) showed a lytic effect predominantly on GNB, whereas phages specific for Gram Positive Cocci (GPC) showed a lytic effect predominantly on GPC.


Phage therapy can be a promising alternative to antibacterial therapy for the treatment of patients with severe MDR bacterial infections.