Immobilization of proteases on chitosan for the development of films with anti-biofilm properties.

Bacterial resistance due to biofilm formation-particularly Staphylococci biofilms-is associated with multiple problems in medical settings where biofilms can colonize medical indwelling devices and cause nosocomial infections. It was against this backdrop that we explored the anti-biofilm activities of a set of proteases against biofilm formation by Staphylococcus aureus, Listeria monocytogenes and Pseudomonas aeruginosa. The selected screened enzymes were immobilized on chitosan to obtain films with anti-biofilm activities. Immobilization efficiency was about 94% for protease from Bacillus licheniformis and reached up to 96% for Neutrase. In vitro assays performed in brain heart infusion (BHI) broth using the Biofilm Ring Test highlighted that immobilized enzymes were efficient against biofilms of Staphylococci cultures, especially protease from B. licheniformis and Neutrase from Bacillus amyloliquefaciens.

Anti-biofilm activity: a function of Klebsiella pneumoniae capsular polysaccharide.

Competition and cooperation phenomena occur within highly interactive biofilm communities and several non-biocides molecules produced by microorganisms have been described as impairing biofilm formation. In this study, we investigated the anti-biofilm capacities of an ubiquitous and biofilm producing bacterium, Klebsiella pneumoniae. Cell-free supernatant from K. pneumoniae planktonic cultures showed anti-biofilm effects on most Gram positive bacteria tested but also encompassed some Gram negative bacilli. The anti-biofilm non-bactericidal activity was further investigated on Staphylococcus epidermidis, by determining the biofilm biomass, microscopic observations and agglutination measurement through a magnetic bead-mediated agglutination test. Cell-free extracts from K. pneumoniae biofilm (supernatant and acellular matrix) also showed an influence, although to a lesser extend. Chemical analyses indicated that the active molecule was a high molecular weight polysaccharide composed of five monosaccharides: galactose, glucose, rhamnose, glucuronic acid and glucosamine and the main following sugar linkage residues [→ 2)-α-L-Rhap-(1 →]; [→ 4)-α-L-Rhap-(1 →]; [α-D-Galp-(1 →]; [→ 2,3)-α-D-Galp-(1 →]; [→ 3)-ß-D-Galp-(1 →] and, [→ 4)-ß-D-GlcAp-(1 →]. Characterization of this molecule indicated that this component was more likely capsular polysaccharide (CPS) and precoating of abiotic surfaces with CPS extracts from different serotypes impaired the bacteria-surface interactions. Thus the CPS of Klebsiella would exhibit a pleiotropic activity during biofilm formation, both stimulating the initial adhesion and maturation steps as previously described, but also repelling potential competitors.

High-throughput screening of metal-N-heterocyclic carbene complexes against biofilm formation by pathogenic bacteria.

A set of molecules including a majority of metal-N-heterocyclic carbene (NHC) complexes (metal=Ag, Cu, and Au) and azolium salts were evaluated by high-throughput screening of their activity against biofilm formation associated with pathogenic bacteria. The anti-planktonic effects were compared in parallel. Representative biofilm-forming strains of various genera were selected (Listeria, Pseudomonas, Staphylococcus, and Escherichia). All the compounds were tested at 1 mg L(-1) by using the BioFilm Ring Test. An information score (IS, sum of the activities) and an activity score (AS, difference between anti-biofilm and anti-planktonic activity) were determined from normalized experimental values to classify the most active molecules against the panel of bacterial strains. With this method we identified lipophilic Ag(I) and Cu(I) complexes possessing aromatic groups on the NHC ligand as the most efficient at inhibiting biofilm formation.