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Open Access Highly Accessed Research article

N-acetylcysteine inhibit biofilms produced by Pseudomonas aeruginosa

Tiemei Zhao and Youning Liu*

Author Affiliations

Department of Respiratory diseases, Chinese PLA General Hospital, Beijing, China

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BMC Microbiology 2010, 10:140  doi:10.1186/1471-2180-10-140

Published: 12 May 2010

Abstract

Background

Pseudomonas aeruginosa is a common pathogen in chronic respiratory tract infections. It typically makes a biofilm, which makes treatment of these infections difficult. In this study, we investigated the inhibitory effects of N-acetylcysteine (NAC) on biofilms produced by P. aeruginosa.

Results

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.

Conclusions

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.