Synergistic bactericidal activity of a naturally isolated phage and ampicillin against urinary tract infecting Escherichia coli O157

Bacteriophages are infectious replicating entities that are under consideration as
antimicrobial bioagents to control bacterial infections. As an alternative or supplement to antibiotics,
bacteriophages can be used to circumvent the resistance to existing antibiotics. The aim of this study
was to assess the synergistic effect of a naturally isolated phage and ampicillin against Escherichia coli
O157.
Materials and Methods: In the present study, a natural phage against E. coli O157 was isolated, the
morphology and molecular characteristics of the phage were identified, and the combination of
bacteriophage and antibiotic to combat clinically isolated drug-resistant E. coli O157 was evaluated.
Results: The results showed the synergistic action between a naturally isolated phage and ampicillin
in solid (disk diffusion test) and liquid culture media. Addition of the isolated phage, gT0E.co-MGY2, to
the microbial lawn of bacteria in modified antibiotic disk diffusion test, altered susceptibility pattern
of E. coli O157 from resistant to sensitive based on the inhibition zones. Combinations of bacteriophage
and ampicillin significantly enhanced the killing of bacterial strainswhen compared to treatment with
ampicillin or phage alone in liquid culture. Moreover, it lasted few hours for ampicillin to reverse the
growth of E. coli O157, while the bacteriophage and combination treatment stopped the proliferation
of bacteria from the beginning, and this can compensate the delayed onset of antibiotic action.
Conclusion: The synergistic action of bacteriophages and antibiotics is an alternative that cannot only
be effective against bacterial infections but also contribute to the reduction of antibiotic resistance.