N-acetylcysteine inhibit biofilms produced by Pseudomonas aeruginosa

We found that minimum inhibitory concentrations (MICs) of NAC for most isolates of P. aeruginosa were 10 to 40 mg/ml, the combination of NAC and ciprofloxacin (CIP) demonstrated either synergy (50%) or no interaction (50%) against the P. aeruginosa strains. NAC at 0.5 mg/ml could detach mature P. aeruginosa biofilms. Disruption was proportional to NAC concentrations, and biofilms were completely disrupted at 10 mg/ml NAC. Analysis using COMSTAT software also showed that PAO1 biofilm biomass decreased and its heterogeneity increased as NAC concentration increased. NAC and ciprofloxacin showed significant killing of P. aeruginosa in biofilms at 2.5 mg/ml and > 2 MIC, respectively (p < 0.01). NAC-ciprofloxacin combinations consistently decreased viable biofilm-associated bacteria relative to the control; this combination was synergistic at NAC of 0.5 mg/ml and CIP at 1/2MIC (p < 0.01). Extracellular polysaccharides (EPS) production by P. aeruginosa also decreased by 27.64% and 44.59% at NAC concentrations of 0.5 mg/ml and 1 mg/ml.NAC has anti-bacterial properties against P. aeruginosa and may detach P. aeruginosa biofilms. Use of NAC may be a new strategy for the treatment of biofilm-associated chronic respiratory infections due to P. aeruginosa, although it would be appropriate to conduct clinical studies to confirm this.Pseudomonas aeruginosa is a known common pathogen in respiratory tract infections. These diseases are usually chronic, such as pulmonary infections in intubated patients and for patients with cystic fibrosis (CF), bronchiectasis, diffuse panbronchiolitis [1,2] and chronic obstructive pulmonary disease (COPD). One reason why treating these infections is difficult is the production of biofilms by P. aeruginosa [3]. Organisms in the biofilm become more resistant than planktonic bacteria to physical and chemical attacks, such as by chemotherapeutic reagents. Discovering substances that inhibit biofilm formation and/or disrupt established biofilms is essen