Biofilm formation in uropathogenic strains of Proteus mirabilis and their susceptibility to poly(epsilon-lysine) dendron

Abstract

Proteus mirabilis is the main aetiological bacteria in catheter-associated urinary tract infections (CAUTI). The ability of P. mirabilis to form biofilms plays an important role in the pathogenesis of CAUTI and there are currently no effective antibiotic therapies. Hence, the aim of this study was to detect the growth and biofilm forming ability of P. mirabilis human isolates on 96-well microtitre plates, and study the antimicrobial effect of poly(epsilon-lysine) dendron molecules on the P. mirabilis biofilms. Eight strains isolated from human urinary tract infections and verified as P. mirabilis, were obtained from the Royal Sussex County Hospital, Brighton, UK. The biofilm forming potential of the selected strains was investigated over 24 hours in 96-well microtitre plates. A clinically relevant concentration of bacteria (10 7 CFU/ml) was incubated in triplicate in Luria-Berthani growth medium. Analysis of the biofilms was performed using crystal violet staining and microscopic observations. P. mirabilis strains with the highest biofilm forming ability were selected for their antimicrobial study. Poly(epsilon-lysine) dendron (generation three) were synthesised via solid-phase peptide synthesis, using Fmoc-protected amino acids and characterised with mass spectrometry and high-performance liquid chromatography. The dendron (1– 0.25 mg/ml) was then co-incubated with P. mirabilis bacteria for 24 hours at 37°C, and the corresponding effect on biofilm formation was assessed as above. Statistical analyses were performed using analysis of variance (ANOVA), with statistical significance defined as P 70 %), by decreasing exopolysaccharide production in a dose-dependent manner. These findings suggest that poly(epsilon-lysine) dendron could have a role in the design of alternative antimicrobial agents for control of P. mirabilis biofilm-related infections. Future studies will focus on the dendron’s ability to eradicate preformed biofilms.