The increasing risk of antibiotic failure in the treatment of Pseudomonas aeruginosa infections is largely related to the production of a wide range of virulence factors. The use of non-thermal plasma (NTP) is a promising alternative to antimicrobial treatment. Nevertheless, there is still a lack of knowledge about the effects of NTP on the virulence factors production. We evaluated the ability of four NTP-affected P. aeruginosa strains to re-form biofilm and produce Las-B elastase, proteases, lipases, haemolysins, gelatinase or pyocyanin. Highly strains-dependent inhibitory activity of NTP against extracellular virulence factors production was observed. Las-B elastase activity was reduced up to 82% after 15-min NTP treatment, protease activity and pyocyanin production by biofilm cells was completely inhibited after 60 min, in contrast to lipases and gelatinase production, which remained unchanged. However, for all strains tested, a notable reduction in biofilm re-development ability was depicted using spinning disc confocal microscopy. In addition, NTP exposure of mature biofilms caused disruption of biofilm cells and their dispersion into the environment, as shown by transmission electron microscopy. This appears to be a key step that could help overcome the high resistance of P. aeruginosa and its eventual elimination, for example in combination with antibiotics still highly effective against planktonic cells.

• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Biofilms MeSH
• Endopeptidases pharmacology   MeSH
• Virulence Factors MeSH
• Hemolysin Proteins pharmacology   MeSH
• Humans MeSH
• Pancreatic Elastase MeSH
• Plankton MeSH
• Plasma Gases * pharmacology   MeSH
• Peptide Hydrolases MeSH
• Pseudomonas Infections * MeSH
• Pseudomonas aeruginosa MeSH
• Pyocyanine MeSH
• Quorum Sensing MeSH
• Gelatinases pharmacology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Pterostilbene (PTE), a dimethylated analogue of resveratrol, mostly contained in Vitis vinifera leaves or in other plant sources is well-known for its antioxidant activity. Due to its bioavailability, low hydrophilicity and thus ability to penetrate hydrophobic biological membranes it was found to be an antimicrobial agent. These properties of PTE offer the possibility of its use in the treatment of microbial infections. The emergence of antibiotic resistance of microorganisms is often caused by their ability to form biofilm; new substances with antibiofilm activity are therefore sought. The representatives of opportunistic pathogenic gram-positive and gram-negative bacteria as well as fungi were used for the determination of minimum inhibitory concentrations (MIC50 and MIC80), minimum biofilm inhibitory concentrations (MBIC50 and MBIC80) and minimum biofilm eradication concentrations (MBEC50 and MBEC80) of PTE and commonly used antibiotics erythromycin, polymyxin B or antimycotic amphotericin B. Total biofilm biomass was investigated by crystal violet staining, and the results were confirmed using microscopic techniques. The most significant antibiofilm action was proved for gram-positive cocci, e.g., MBEC50 of PTE for all strains of Staphylococcus epidermidis tested was 25 mg/L. By contrast, the antibiotic ERM did not exhibit antibiofilm activity in most cases. The permeabilization of cell membranes of gram-positive cocci biofilm by MBIC50 and MBEC50 of PTE was confirmed by LIVE/DEAD staining using spinning disc confocal microscopy. PTE significantly influenced the ability of gram-positive cocci to form biofilm and it effectively eradicated pre-formed biofilm in vitro; its potential for the treatment of biofilm-associated infections of Staphylococcus spp. or Enterococcus faecalis is thus apparent.

• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Antioxidants pharmacology   MeSH
• Biofilms drug effects   growth & development   MeSH
• Enterococcus faecalis drug effects   MeSH
• Gram-Negative Bacteria drug effects   MeSH
• Gram-Positive Bacteria drug effects   MeSH
• Gram-Positive Cocci drug effects   MeSH
• Plant Leaves chemistry   MeSH
• Microbial Sensitivity Tests MeSH
• Pseudomonas aeruginosa drug effects   MeSH
• Plant Extracts pharmacology   MeSH
• Staphylococcus epidermidis drug effects   MeSH
• Stilbenes pharmacology   MeSH
• Vitis chemistry   MeSH
• Publication type
• Journal Article MeSH

The biofilms of filamentous-forming fungi are a novel and still insufficiently understood research topic. We have studied Aspergillus fumigatus, an ubiquitous opportunistic pathogenic fungus, as a representative model for a study of biofilm formation by filamentous fungi and for assessing the potential anti-biofilm activity of natural substances. The activity of antibiotic amphotericin B and selected natural substances: baicalein, chitosan and rhamnolipid was studied. The minimum suspension inhibitory concentrations (MIC) were determined and the biofilm susceptibility was investigated by determining the metabolic activity of sessile cells (XTT assay) and total biofilm biomass (crystal violet staining). Significant time-dependent differences in substances' anti-biofilm activity were observed. Images of A. fumigatus biofilm were obtained by Cellavista automatic light microscope and spinning disc confocal microscopy. Baicalein and rhamnolipid were not found as suitable substances for inhibition of the A. fumigatus biofilm formation, as neither of the substances inhibited the sessile cells metabolic activity or the total biofilm biomass even at tenfold MIC after 48 h. In contrast, chitosan at 10 × MIC (25 µg mL(-1)), suppressed the biofilm metabolic activity by 90 % and the total biofilm biomass by 80 % even after 72 h of cultivation. Amphotericin B inhibited only 14 % of total biofilm biomass (crystal violet staining) and 35 % of metabolic activity (XTT assay) of adherent cells under the same conditions. Our results therefore suggest chitosan as potential alternative for treating A. fumigatus biofilm-associated infections.

• MeSH
• Amphotericin B pharmacology   MeSH
• Antifungal Agents pharmacology   MeSH
• Aspergillus fumigatus drug effects   physiology   MeSH
• Biofilms drug effects   MeSH
• Chitosan pharmacology   MeSH
• Flavanones pharmacology   MeSH
• Glycolipids pharmacology   MeSH
• Microbial Sensitivity Tests MeSH
• Publication type
• Journal Article MeSH