Combination of phages and antibiotics with enhanced killing efficacy against dual-species bacterial communities in a three-dimensional lung epithelial model

<i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i> are opportunistic pathogens commonly found in biofilm-associated polymicrobial respiratory infections that are challenging to control. Studies performed in laboratory standard conditions suggest that bacterio(phages) and antibiotic combinations are more active against bacterial communities and biofilms than each agent alone. The purpose of this work was to study the antibacterial efficacy of phage-antibiotic combinations using an <i>in vivo</i>-like three-dimensional lung epithelial model that mimics aspects of the parental tissue, colonized by a mixed bacterial community of <i>P. aeruginosa</i> and <i>S. aureus</i>. The bacterial population was targeted by phages specific to <i>P. aeruginosa</i> and/or gentamicin and ciprofloxacin. The results showed that <i>P. aeruginosa</i> was eradicated from the dual-species community when phage treatment was followed by gentamicin and was significantly reduced when followed by ciprofloxacin. Moreover, applying phages first followed by antibiotics demonstrated superior antibacterial activity compared to simultaneous treatment or treatments with the reverse order of application. This approach also reduced the <i>S. aureus</i> population but not as significant as the <i>P. aeruginosa</i> population. Using an <i>in vivo</i>-like model we demonstrated that phages and antibiotics are effective against dual-species bacterial communities, particularly targeting the <i>P. aeruginosa</i> population. However, but the sequence in which these antimicrobials are applied significantly in fluences the effectiveness of bacterial killing.