A broad-host range coliphage against a clinically isolated E. coli O157: isolation and characterization

Escherichia coli O157 is one of the common and problematic pathogens, particularly in developing countries. To isolate a phage against this pathogen, a total of 32 water samples were enriched for phage and two of these samples were found to contain lytic phages that grow on and kill enterohaemorrhagic E. coli serotype O157. Following the primary evaluation, the most efficient phage was chosen for further characterization. The multiplicity of infection, morphology, killing efficiency and bacterial host range were determined under controlled conditions in the laboratory. Isolated phage was designated gBSN-MGB13. According to transmission electron microscopy, this lytic phage morphologically belonged to the myoviridae family. Based on phage efficiency test, a multiplicity of infection of 5 logs of gBSN-MGB13 resulted in 50% reduction in viable bacterial cell count after 20 min incubation in 37 °C without shaking. Since gBSN-MGB13 is a broad-host range phage and effective against several pathogenic species, E. coli O157 as well as Proteus vulgaris and Pseudomonas aeruginosa, its applications could be investigated in complex infections as combinatory therapy. This is an exciting aspect of phage therapy.