BAG3 protein, a member of the BAG co-chaperones family, sustains cell survival, through its interaction with the heat shock protein (HSP) 70, in a variety of normal and neoplastic cell types. bag3 gene expression is induced by stressful stimuli. Here we report for the first time that two of the three putative heat shock-responsive elements (HSEs) in bag3 promoter interact with the heat shock factor (HSF) 1 in vitro and in vivo. Furthermore, downmodulation of HSF1 protein levels by specific small interfering (si) RNAs results in reducing BAG3 protein levels, indicating that the transcription factor plays a major role in bag3 gene expression. Because of the anti-apoptotic role of BAG3 protein, these results disclose a previously unrecognized pathway, through which HSF1 maintains cell survival.

The present study was undertaken in order to understand more about the interaction occurring between S. maltophilia and P. aeruginosa, which are frequently co-isolated from CF airways. For this purpose, S. maltophilia RR7 and P. aeruginosa RR8 strains, co-isolated from the lung of a chronically infected CF patient during a pulmonary exacerbation episode, were evaluated for reciprocal effect during planktonic growth, adhesion and biofilm formation onto both polystyrene and CF bronchial cell monolayer, motility, as well as for gene expression in mixed biofilms. P. aeruginosa significantly affected S. maltophilia growth in both planktonic and biofilm cultures, due to an inhibitory activity probably requiring direct contact. Conversely, no effect was observed on P. aeruginosa by S. maltophilia. Compared with monocultures, the adhesiveness of P. aeruginosa on CFBE41o- cells was significantly reduced by S. maltophilia, which probably acts by reducing P. aeruginosa's swimming motility. An opposite trend was observed for biofilm formation, confirming the findings obtained using polystyrene. When grown in mixed biofilm with S. maltophilia, P. aeruginosa significantly over-expressed aprA, and algD—codifying for protease and alginate, respectively—while the quorum sensing related rhlR and lasI genes were down-regulated. The induced alginate expression by P. aeruginosa might be responsible for the protection of S. maltophilia against tobramycin activity we observed in mixed biofilms. Taken together, our results suggest that the existence of reciprocal interference of S. maltophilia and P. aeruginosa in CF lung is plausible. In particular, S. maltophilia might confer some selective “fitness advantage” to P. aeruginosa under the specific conditions of chronic infection or, alternatively, increase the virulence of P. aeruginosa thus leading to pulmonary exacerbation.

Patients with cystic fibrosis require pharmacological treatment against chronic lung infections. The alpha-helical antimicrobial peptides BMAP-27 and BMAP-28 have shown to be highly active in vitro against planktonic and sessile forms of multidrug-resistant Pseudomonas aeruginosa, Staphylococcus aureus, and Stenotrophomonas maltophilia cystic fibrosis strains. To develop small antibacterial peptides for therapeutic use, we tested shortened/modified BMAP fragments, and selected the one with the highest in vitro antibacterial activity and lowest in vivo acute pulmonary toxicity. All the new peptides have shown to roughly maintain their antibacterial activity in vitro. The 1-18 N-terminal fragment of BMAP-27, showing MIC90 of 16 µg/ml against P. aeruginosa isolates and strain-dependent anti-biofilm effects, showed the lowest pulmonary toxicity in mice. However, when tested in a murine model of acute lung infection by P. aeruginosa, BMAP-27(1-18) did not show any curative effect. If exposed to murine broncho-alveolar lavage fluid BMAP-27(1-18) was degraded within 10 min, suggesting it is not stable in pulmonary environment, probably due to murine proteases. Our results indicate that shortened BMAP peptides could represent a starting point for antibacterial drugs, but they also indicate that they need a further optimization for effective in vivo use.

BackgroundStaphylococcus pseudintermedius is an opportunistic pathogen recognized as the leading cause of skin, ear, and post-operative bacterial infections in dogs and cats. Zoonotic infections have also recently been reported causing endocarditis, infection of surgical wounds, rhinosinusitis, and catheter-related bacteremia. The aim of the present study is to evaluate, for the first time, the pathogenic potential of S. pseudintermedius isolated from a human infection. To this end, strain DSM 25713, which was recently isolated from a wound of a leukemic patient who underwent a bone marrow transplantation, was investigated for biofilm formation and antibiotic-resistance under conditions relevant for wound infection.ResultsThe effect of pH (5.5, 7.1, and 8.7) and the presence of serum (diluted at 1:2, 1:10, and 1:100) on biofilm formation was assessed through a crystal violet assay. The presence of serum significantly reduced the ability to form biofilm, regardless of the pH value tested. In vitro activity of eight antibiotics against biofilm formation and mature 48 h-old biofilms was comparatively assessed by crystal violet assay and viable cell count, respectively. Antibiotics at sub-inhibitory concentrations reduced biofilm formation in a dose-dependent manner, although cefoxitin was the most active, causing a significant reduction already at 1/8xMIC. Rifampicin showed the highest activity against preformed biofilms (MBEC90: 2xMIC). None of the antibiotics completely eradicated the preformed biofilms, regardless of tested concentrations. Confocal and electron microscopy analyses of mature biofilm revealed a complex “mushroom-like” architecture consisting of microcolonies embedded in a fibrillar extracellular matrix.ConclusionsFor the first time, our results show that human wound-associated S. pseudintermedius is able to form inherently antibiotic-resistant biofilms, suggestive of its pathogenic potential, and consistent with recent reports of zoonotic infections.

Exposure to ELF-MF represents a possible new approach for treatment of biofilm-associated cystic fibrosis lung infections.