Bandara, H. M. H. N., Herpin, M. J., Kolacny, D., Harb, A., Romanovicz, D., and Smyth, H. D. C.
The challenge of eliminating Pseudomonas aeruginosainfections, such as in cystic fibrosis lungs, remains unchanged due to the rapid development of antibiotic resistance. Poor drug penetration into dense P. aeruginosabiofilms plays a vital role in ineffective clearance of the infection. Thus, the current antibiotic therapy against P. aeruginosabiofilms need to be revisited and alternative antibiofilm strategies need to be invented. Fungal quorum sensing molecule (QSM), farnesol, appears to have detrimental effects on P. aeruginosa. Thus, this study aimed to codeliver naturally occurring QSM farnesol, with the antibiotic ciprofloxacin as a liposomal formulation to eradicate P. aeruginosabiofilms. Four different liposomes (with ciprofloxacin and farnesol, Lcip+far; with ciprofloxacin, Lcip; with farnesol, Lfar; control, Lcon) were prepared using dehydration–rehydration method and characterized. Drug entrapment and release were evaluated by spectrometry and high performance liquid chromatography (HPLC). The efficacy of liposomes was assessed using standard biofilm assay. Liposome-treated 24 h P. aeruginosabiofilms were quantitatively assessed by XTT reduction assay and crystal violet assay, and qualitatively by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). Ciprofloxacin release from liposomes was higher when encapsulated with farnesol (Lcip+far) compared to Lcip(3.06% vs 1.48%), whereas farnesol release was lower when encapsulated with ciprofloxacin (Lcip+far) compared to Lfar(1.81% vs 4.75%). The biofilm metabolism was significantly lower when treated with Lcip+faror Lcipcompared to free ciprofloxacin (XTT, P< 0.05). When administered as Lcip+far, the ciprofloxacin concentration required to achieve similar biofilm inhibition was 125-fold or 10-fold lower compared to free ciprofloxacin or Lcip, respectively (P< 0.05). CLSM and TEM confirmed predominant biofilm disruption, greater dead cell ratio, and increased depth of biofilm killing when treated with Lcip+farcompared to other liposomal preparations. Thus, codelivery of farnesol and ciprofloxacin is likely to be a promising approach to battle antibiotic resistant P. aeruginosabiofilms by enhancing biofilm killing at significantly lower antibiotic doses.