| Summary: | <p>Abstract</p> <p>Background</p> <p><it>Pseudomonas aeruginosa </it>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 <it>P. aeruginosa</it>.</p> <p>Results</p> <p>We found that minimum inhibitory concentrations (MICs) of NAC for most isolates of <it>P. aeruginosa </it>were 10 to 40 mg/ml, the combination of NAC and ciprofloxacin (CIP) demonstrated either synergy (50%) or no interaction (50%) against the <it>P. aeruginosa </it>strains. NAC at 0.5 mg/ml could detach mature <it>P. aeruginosa </it>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 <it>P. aeruginosa </it>in biofilms at 2.5 mg/ml and > 2 MIC, respectively (<it>p </it>< 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 (<it>p</it> < 0.01). Extracellular polysaccharides (EPS) production by <it>P. aeruginosa </it>also decreased by 27.64% and 44.59% at NAC concentrations of 0.5 mg/ml and 1 mg/ml.</p> <p>Conclusions</p> <p>NAC has anti-bacterial properties against <it>P. aeruginosa </it>and may detach <it>P. aeruginosa </it>biofilms. Use of NAC may be a new strategy for the treatment of biofilm-associated chronic respiratory infections due to <it>P. aeruginosa</it>, although it would be appropriate to conduct clinical studies to confirm this.</p>
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