Antimicrobial, antiadhesive and antibiofilm potential of lipopeptides synthesised by Bacillus subtilis, on uropathogenic bacteria.

The aim of this study was to investigate the antimicrobial effect of lipopeptide biosurfactants from surfactin, iturin and fengycin families, synthesised by the Bacillus subtilis I'1a strain, on uropathogenic bacteria, including the effects on planktonic growth, processes of biofilm formation and dislodging. Antimicrobial activity was tested against 32 uropathogenic strains belonging to 12 different species of Gram-negative and Gram-positive bacteria. The sensitivity of 25 tested bacterial strains to the B. subtilis I'1a filtrate was confirmed by an agar diffusion assay. None of the strains seemed to be sensitive to pure surfactin at concentrations ranging from 0.1 mg × ml(-1) to 0.4 mg ml(-1). After the treatment of uropathogens with B. subtilis lipopeptides, the metabolic activity of planktonic cells was inhibited by 88.05±3.96% in the case of 21 studied uropathogens, the process of biofilm formation was reduced by 88.15±4.77% in the case of 24 uropathogens and mature biofilms of 18 strains were dislodged by about 81.20±4.72%. Ten strains of uropathogenic bacteria were selected to study the antimicrobial activity of surfactin (concentrations 0.1, 0.2 and 0.4 mg × ml(-1)). Surfactin had no influence on the metabolic activity of planktonic forms of uropathogens, however, biofilms of 5 tested strains were reduced by 64.77±9.05% in the presence of this biosurfactant at the concentration 0.1 mg × ml(-1). The negative effect of the compound on the biofilm formation process was observed at all concentrations used. The above-described results were fully confirmed by CLSM. It could suggest that synergistic application of biosurfactants could be efficient in uropathogen eradication.