Combined Bacteriophage and Antibiotic Treatment Prevents Pseudomonas aeruginosa Infection of Wild Type and cftr- Epithelial Cells

Abstract

With the increase of infections due to multidrug resistant bacterial pathogens and the shortage of antimicrobial molecules with novel targets, interest in bacteriophages as a therapeutic option has regained much attraction. Before the launch of future clinical trials, <i>in vitro</i> studies are required to better evaluate the efficacies and potential pitfalls of such therapies. Here we studied in an <i>ex vivo</i> human airway epithelial cell line model the efficacy of phage and ciprofloxacin alone and in combination to treat infection by <i>Pseudomonas aeruginosa</i>. The Calu-3 cell line and the isogenic CFTR knock down cell line (<i>cftr</i>-) infected apically with <i>P. aeruginosa</i> strain PAO1 showed a progressive reduction in transepithelial resistance during 24 h. Administration at 6 h p.i. of single phage, phage cocktails or ciprofloxacin alone prevented epithelial layer destruction at 24 h p.i. Bacterial regrowth, due to phage resistant mutants harboring mutations in LPS synthesis genes, occurred thereafter both <i>in vitro</i> and <i>ex vivo</i>. However, co-administration of two phages combined with ciprofloxacin efficiently prevented PAO1 regrowth and maintained epithelial cell integrity at 72 p.i. The phage/ciprofloxacin treatment did not induce an inflammatory response in the tested cell lines as determined by nanoString^® gene expression analysis. We conclude that combination of phage and ciprofloxacin efficiently protects wild type and <i>cftr</i>- epithelial cells from infection by <i>P. aeruginosa</i> and emergence of phage resistant mutants without inducing an inflammatory response. Hence, phage-antibiotic combination should be a safe and promising anti-Pseudomonas therapy for future clinical trials potentially including cystic fibrosis patients.