Does Treatment Order Matter? Investigating the Ability of Bacteriophage to Augment Antibiotic Activity against Staphylococcus aureus Biofilms

Abstract

The inability to effectively treat biofilm-related infections is a major clinical challenge. This has been attributed to the heightened antibiotic tolerance conferred to bacterial cells embedded within biofilms. Lytic bacteriophages (phages) have evolved to effectively infect and eradicate biofilm-associated cells. The current study was designed to investigate the ability of phage treatment to enhance the activity of antibiotics against biofilm-forming Staphylococcus aureus. The biofilm positive S. aureus strain ATCC 35556, the lytic S. aureus phage SATA-8505, and five antibiotics (cefazolin, vancomycin, dicloxacillin, tetracycline, and linezolid), used to treat S. aureus infections, were tested in this study. The ability of the SATA-8505 phage to augment the effect of these antibiotics against biofilm-associated S. aureus cells was assessed by exposing them to one of the five following treatment strategies: (i) antibiotics alone, (ii) phage alone, (iii) a combination of the two treatments simultaneously, (iv) staggered exposure to the phage followed by antibiotics, and (v) staggered exposure to antibiotics followed by exposure to phage. The effect of each treatment strategy on biofilm cells was assessed by enumerating viable bacterial cells. The results demonstrate that the treatment of biofilms with either SATA-8505, antibiotics, or both simultaneously resulted in minimal reduction of viable biofilm-associated cells. However, a significant reduction [up to 3 log colony forming unit (CFU)/mL] was observed when the phage treatment preceded antibiotics. This effect was most pronounced with vancomycin and cefazolin which exhibited synergistic interactions with SATA-8505, particularly at lower antibiotic concentrations. This in vitro study provides proof of principle for the ability of phages to augment the activity of antibiotics against S. aureus biofilms. Our results also demonstrate that therapeutic outcomes can be influenced by the sequence in which these therapeutic agents are administered, and the nature of their interactions. Further investigation into the interactions between lytic phages and antibiotics against various biofilm-forming organisms is important to direct future clinical translation of efficacious antibiotic–phage combination therapeutic strategies.

Bacteriophages as Adjuvant to Antibiotics for the Treatment of Periprosthetic Joint Infection Caused by Multidrug-Resistant Pseudomonas aeruginosa

“…They are able to degrade biofilm matrix, thereby enhancing the efficacy of antibiotics and reducing the concentration of antibiotics required to eradicate infection (13,14). Recent studies have demonstrated that phages can eradicate biofilms by their synergistic action with antibiotics (15,16).…”

Phage-Antibiotic Synergy via Delayed Lysis

“…Lysogenized phage P1 in E. coli showed PAS in the presence of ciprofloxacin, and a P1 Ref endonuclease amplified the lytic cycle when a bacterial SOS response was induced by DNA damage (11). A synergistic effect was also observed when removing P. aeruginosa and S. aureus biofilms (12,13). The degree of synergy depended upon the specific antibiotic used (14).…”

Evaluation of Sb-1 bacteriophage activity in enhancing antibiotic efficacy against biofilm, degrading the exopolysaccharide matrix and targeting persister cells of Staphylococcus aureus

“…A similar effect was also observed for vancomycin and ciprofloxacin. The promising potential of the phage-antibiotic staggered treatment has been recently highlighted by other two groups (14, 15), and may be related to the potential antagonistic effect of simultaneous treatment with antibiotics, which inhibit and/or kill bacteria, and bacteriophages, which require replicating bacterial cells to propagate (33, 34).…”

“…Ryan et al showed that a synergistic effect of cefotaxime was observed when used in combination with the T4 phage against Escherichia coli biofilm (13). Two independent studies also demonstrated that pre-treating Pseudomonas aeruginosa (14) and S. aureus (15) biofilms with bacteriophages before antibiotic administration determined a major reduction of bacterial viability compared to the effect observed with the simultaneous administration of these therapeutic agents. However, none of the above-mentioned papers investigated the mechanisms through which phages can enhance antibiotics activity against biofilms.…”