The Effect of Bacteriophage T4 and PB-1 Infection with Tobramycin on the Survival of Escherichia coli and Pseudomonas aeruginosa Biofilms
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Populations of bacterial cells growing as biofilms demonstrate greater resistance to antibiotics compared to planktonic cells. Consequently, there is renewed interest in bacteriophage therapy as an alternative to antimicrobial chemotherapy. Although phages may be more effective than antibiotics alone in reducing biofilm mass, they are often not able to eradicate the biofilm. The aim of this study was to determine if bacteriophage in combination with an antimicrobial would be more effective in decreasing biofilm mass compared to the use of either antibiotic or phage alone. It was also of interest to determine if the combination of phage and antibiotic could reduce the emergence of either antibiotic or phage resistant mutants. Escherichia coli or Pseudomonas aeruginosa 48 h biofilms were challenged with phage T4 or PB-1, respectively, in combination with tobramycin. At 6 h and 24 h post challenge, total cells, tobramycin resistant cells, and phage resistant cells were determined. The use of phage in combination with antibiotic resulted in an enhanced reduction of E. coli biofilms compared to either phage or antibiotic alone. The combination of phage and antibiotic resulted in a reduction in P. aeruginosa biofilms compared to phage alone. The combination of phage with antibiotic resulted in a reduced emergence of phage resistant (39% to 99%) and antibiotic resistant (26% to >99%) cells compared to treatment with either phage or antibiotic alone. The study suggests the combination of phage and antibiotic is more effective in reducing both biofilm mass and the emergence of resistance than the use of either phage or antibiotic alone. The study also suggests biofilm survival is dependent on the phage-host system.