This study was designed to evaluate the effect of phage-antibiotic synergy in reducing antibiotic resistance. The initial numbers of Staphylococcus aureus treated with ciprofloxacin, phages, and combination were significantly reduced by 3.47, 4.62, and 5.75 log CFU/mL, respectively, at the early 12 h of incubation. The combination treatment most effectively inhibited the growth of S. aureus, showing more than 4 log reduction in 18 h of incubation at 37°C. The significant reduction in biofilm formation by S. aureus was observed at the combination treatment (3.91 log). Ciprofloxacin-treated S. aureus cells became resistant to both ciprofloxacin and phage, showing the mutant frequencies of 27% and 25%, respectively, whereas no antibiotic- and phage-resistant S. aureus cells were observed at the combined treatment of ciprofloxacin and phages. These results provide useful information for reducing the risk of antibiotic resistance in human and food animals.
Keywords: Staphylococcus aureus; antibiotic resistance; ciprofloxacin; mutant frequency; phage-antibiotic combination.