Comparative Evaluation Of The Activity Of Staphylococcal Bacteriophages With Different Classes Of Antibiotics

Introduction. Phage–antibiotic synergy (PAS) is a novel concept that highlights the combined use of bacteriophages and antibiotics in the fight against bacterial infections. PAS shows promise in overcoming antimicrobial resistance, as phages can enhance the bacterial sensitivity to antibiotics and influence biofilms, resistance mechanisms, and the metabolic activity of microorganisms. In addition to these positive effects, an antagonistic effect has also been described in the interaction between bacteriophages and certain types of antimicrobial agents. Understanding the dynamics of this interaction is crucial for the development of innovative therapeutic strategies against multidrug-resistant pathogens.

Methods. To determine the effect of different antibiotics on bacteriophage reproduction, a modification of the disk-diffusion method was used. For this, a daily culture of host bacteria and the corresponding model phage strain were added to a melted and cooled medium. After the medium solidified, antibiotic disks were placed on its surface. The effect of antibiotics on bacteriophage reproduction was assessed after 24 hours by determining the inhibition or enhancement of plaque formation at the boundary of the bacterial culture growth inhibition zone. The bacterial test culture used was Staphylococcus aureus DSM 799, and the model bacteriophage was phage St12f.

Results. The experimental results showed that different classes of antibiotics affected the reproduction of the bacteriophage St12f in different ways. Three types of effects were observed: synergy (the enhancement of plaque formation in the zone with sublethal doses of antibiotics), antagonism (reductions in the number and size of plaques), and neutral action. Specifically, synergistic effects were observed with penicillins, cephalosporins, and fluoroquinolones; antagonistic effects were noted with certain antibiotics from the groups of macrolides, tetracyclines, oxazolidinones, rifamycins, sulfonamides, and phenicols. Aminoglycosides exhibited neutral effects.

Conclusions. We believe that studying phage–antibiotic interactions should become an essential component of the combined use of phages and antibiotics for the treatment of various bacterial infections.