Our research showed that the amounts of EPS produced by P. aeruginosa strains were also significantly inhibited by 0.5 and 1 mg/ml of NAC. Taking into account the results given above, NAC may be a potent agent for treating P. aeruginosa biofilms associated infections, and can be used

in combination with ciprofloxacin. Stafanger [21] studied the effect of peroral NAC in patients with cystic fibrosis and chronic pulmonary P. aeruginosa infection, a significant improvement of the spirometric values was proved after NAC treatment in the patients with peak expiratory flow rate below or equal to this website 70% of predicted normal values. Stey [22] reviewed the publications on the effect of oral NAC in chronic bronchitis, eleven randomized controlled NAC trials were analysed (a total of 2,011 patients), concluded that oral NAC reduced the risk of exacerbation and improved symptoms in patients with chronic bronchitis compared with palcebo. But the benefit it achieved still remains unclear. We are not sure whether it took into account the other elements such as anti-bacterial activities and detach biofilms or not? It needs further study. NAC can be administered by nebulization or direct instillation, orally or intravenously. The concentrations tested in our study are much higher than those reach in serum when administer by an intravenous or oral route. Nevertheless, it may be possible that using local respiratory application (10% solution may be used undiluted

for inhalation) obtains Ibrutinib nmr useful concentrations to disrupt biofilms and control biofilm-associated infections of P. aeruginosa. Conclusions In conclusion, our results suggest that NAC has anti-bacterial properties against P. aeruginosa and may detach P. aeruginosa biofilms. It may

be a new strategy for the treatment of biofilm-associated chronic respiratory infections, although it would be appropriate to conduct in vivo animal models and clinical studies to confirm this. Methods Bacterial strains P. aeruginosa Glycogen branching enzyme PAO1 expressing a green fluorescent protein (GFP) plasmid (pMRP9-1) was kindly donated by Dr. E. P. Greenberg (University of Washington, Seattle). An additional 20 strains of P. aeruginosa isolated from respiratory samples were studied. Determination of minimum inhibitory concentrations (MIC) and drug-drug interactions Crystalline NAC (Sigma-Aldrich, USA) was dissolved in distilled water to make a 100 mg/ml solution; the pH of solution was adjusted to 7.2 before use. Stock solution of ciprofloxacin (National Institute for the Control of Pharmaceutical and Biological Products, China) was prepared at concentrations of 4096 μg/ml in the distilled water. MICs of NAC and ciprofloxacin were determined using a broth micro-dilution assay according to Clinical Laboratory Standards Institute (CLSI) guidelines [23]. Each well of a 96-well microtiter plate containing 100 μl from a series of diluted NAC with Mueller-Hintor broth was inoculated with 100 μl of P.