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 Selleck EGFR inhibitor 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 essential for treating these diseases. N-acetylcysteine (NAC) is a mucolytic agent that has anti-bacterial properties. NAC also decreases biofilm formation by a variety of bacteria [4–6] and reduces the production of an extracellular polysaccharide matrix, while promoting the disruption of mature biofilms [4, 7]. The effect of NAC on P. aeruginosa biofilms has not been extensively studied, and a better understanding of bacterial responses to NAC may GSK2126458 facilitate its use as a biofilm inhibitor. Thus, we investigated the effects of NAC for (i) anti-bacterial properties, (ii) detachment of biofilms, (iii) viable cells in biofilms and (iv) production selleck of extracellular polysaccharides (EPS) by P. aeruginosa. Results 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. The minimum inhibitory concentrations (MICs) of NAC for 18 P. aeruginosa isolates were 10 to 40 mg/ml, and MICs for another 2 isolates were > 40 mg/ml. The combination of NAC and ciprofloxacin demonstrated either synergy (50%) or no interaction (50%) against the P. aeruginosa strains; antagonism was not observed. 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 from producers;

10 (50%) were moderate biofilm producers; 7 (35%) were strong biofilm producers. Effects of NAC on biofilms of P. aeruginosa PAO1 and quantitative analysis using COMSTAT software As shown in Figure 1, biofilms were observed using confocal laser scanning microscopy (CLSM) and three-dimensional images were reconstructed by Olympus FV10-ASM1.7 Software. A GFP-plasmid was inserted into PAO1, which allowed the detection of live bacteria by fluorescence. Observed by CLSM, PAO1 grew in a characteristic pattern with a lawn of bacterial growth on the surface. These results showed that NAC disrupted and inhibited PAO1 biofilms, fluorescence and thickness decreased after exposure to NAC, and there was an NAC dose-dependent effect. Almost no fluorescence was detected after 10 mg/ml NAC treatment, indicating that very few to no live PAO1 were present. Decreased GFP detection levels were associated with increasing concentrations of NAC in each fixed scanning area (Figure 2). Figure 1 Biofilms of P.