ABSTRACT
AIMS: This paper presents the potential of environmentally sourced bacteriophages to affect the growth of clinical isolates of Pseudomonas aeruginosa biofilms, and assesses the respective plaque morphotypes presented by each bacteriophage, in vitro. METHODS AND RESULTS: Bacterial host strains were typed for their ability to produce the quorum sensing-controlled virulence factor pyocyanin, and then tested for bacteriophage susceptibility using the spot test method. The bacteriophages were co-administered with ciprofloxacin in order to determine whether the bacteriophages would demonstrate synergistic or antagonistic behaviour to the antibiotic in vitro. Results suggest a potential relationship between the bacteriophage plaque size and biofilm inhibition, where those producing smaller plaques appear to be more effective at reducing bacterial biofilm formation. CONCLUSIONS: This phenomenon may be explained by a high adsorption rate leading to the rapid formation of smaller plaques, and greater biofilm reduction associated with the loss of viable bacterial cells before the cells can adhere to the surface and form a biofilm. Results from the co-administration of bacteriophage and ciprofloxacin suggest that the two work synergistically to affect P. aeruginosa biofilms. SIGNIFICANCE AND IMPACT OF THE STUDY: The data indicate enhanced efficacy of ciprofloxacin by ≥50%. This could offer an alternative strategy for targeting antibiotic-resistant infections.