CAN PHAGES MODIFY ANTIBIOTICS RESISTANCE PROFILE OF E. FAECALIS?

Introduction: Vancomycin-resistant Enterococcus faecalis (VRE) is considered a serious health threat. Moreover, the treatment options available for VRE infections are limited. Therefore, new classes of effective antibacterial agents are urgently required. A possible solution to combat multidrug resistant bacteria is phage therapy. Phages are viruses that target bacteria and are considered as natural bacterial "killers". Moreover, it has been shown that phages can influence bacterial sensitivity to antibiotics. We hypothesized that the antimicrobial resistance of VRE to vancomycin can be modified using anti-VRE phages: EFDG1 and EFLK1.

Methods: VRE bacterial sensitivity was determined using vancomycin E-test before and after phage treatment. Vancomycin activity against VRE that survived phage treatment was evaluated using an ELISA plate reader. The number of living surviving bacteria was evaluated by CFU/mL. While searching for the mechanism bacteria were stained with Wheat Germ Agglutinin-Alexa Fluor 647 conjugate that attaches to vancomycin binding site on the cell wall. The samples were visualized using confocal microscopy.

Results: Vancomycin MIC against VRE decreased following phage treatment. Lower viable counts of VRE were obtained with vancomycin following exposure to EFDG1 and EFLK1 phages. Confocal microscopy showed an increase in the staining of the bacterial cell wall after treatment with phages.

Conclusion: VRE faecalis sensitivity to vancomycin is modified following exposure to anti-VRE phages EFDG1 and EFLK1. The increase in sensitivity may be attributed to an alteration of the cell-wall peptide subunits to which vancomycin binds.