epidermidis biofilms and the reduction in coverage was significant (P<0.001) for strains PAO1,

6750, 14:2, 23:1 and 27:1, but not for 15159. As for the dual-species biofilms shown in Fig. 3, a pronounced effect was seen for selleck chemicals llc strain 14:2. Similar effects were seen with the P. aeruginosa supernatants for the other S. epidermidis strains (Mia and C103), although the effects were less pronounced (data not shown). To determine whether the dispersal effect on S. epidermidis biofilms was due to cell lysis, S. epidermidis cells remaining in the biofilms after exposure to the P. aeruginosa biofilm supernatants were examined with the BacLight LIVE/DEAD stain. For all the S. epidermidis strains (Mia, C103 and C121), over 90% of the cells were viable after treatment

with each of the P. aeruginosa supernatants (data not shown). Protein Tyrosine Kinase inhibitor Similarly, the level of viability of the dispersed cells was over 90% as shown by staining or growth on 110 agar. In order to investigate what might be responsible for the variable effect of the P. aeruginosa strains (PAO1, NCTC 6750, 14:2, 23:1, 27:1 and 15159), biofilm supernatants were investigated for the release of a number of known virulence factors. The type strain PAO1 and the clinical isolate 15159 were found to be positive for the production of the quorum-sensing signal C4-HSL, while all the other strains were negative (Table 1). All the P. aeruginosa strains were positive for pyocyanin production, except 14:2 and 27:1, which were negative in this assay (Table 1). These results indicate that the repertoire of extracellular

products released from the 17-DMAG (Alvespimycin) HCl cells varies according to the strain. The secretion of extracellular proteases from P. aeruginosa cells growing in biofilms was investigated with zymography of culture supernatants (Fig. 5a). This showed differences between the strains in their degree of gelatinase activity. The supernatants from the two laboratory strains: PAO1 and NCTC 6750 as well as the clinical isolate 15159 contained at least three major bands of proteolytic activity at >150, 70 and 50 kDa. The >150 kDa enzyme has been identified previously by immuno-blotting and N-terminal sequencing as a multimeric form of P. aeruginosa elastase (Schmidtchen et al., 2003). In the same study, P. aeruginosa alkaline protease was demonstrated to band at around 50 kDa. This 50 kDa band, but not the higher molecular weight fractions, was also present in supernatants from strains 23:1 and 27:1 while the culture supernatant from biofilms of strain 14:2 appeared to lack any proteolytic activity. SDS-PAGE of the same material under reducing conditions confirmed differences in the extracellular protein profiles between the strains (Fig. 5b). Two different protein banding patterns could be identified, with strains PAO1, NCTC 6750 and 15159 showing a similar pattern and 14:2, 23:1 and 27:1 strains sharing many common bands.