Abstract
BackgroundPseudomonas 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.ResultsWe 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.ConclusionsNAC 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.
Highlights
Pseudomonas aeruginosa is a common pathogen in chronic respiratory tract infections
Susceptibility of P. aeruginosa strains to NAC and the in vitro interactive effects of NAC and ciprofloxacin Twenty P. aeruginosa strains were isolated from respiratory samples
Interpretations of biofilm production Using the criteria of Stepanovic et al, P. aeruginosa strains were divided into the following categories: 3 (15%) were weak biofilm producers; 10 (50%) were moderate biofilm producers; 7 (35%) were strong biofilm producers
Summary
Pseudomonas aeruginosa is a common pathogen in chronic respiratory tract infections. It typically makes a biofilm, which makes treatment of these infections difficult. We investigated the inhibitory effects of Nacetylcysteine (NAC) on biofilms produced by P. aeruginosa. 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].
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