Effect of Human Insulin on the Formation of Catheter-Associated <i>E. coli</i> Biofilms

Abstract

Biofilm formation is essential for the survival and growth of Escherichia coli in catheter-associated infections. Individuals with type 2 diabetes mellitus can excrete insulin and/or glucose in their urine. This population also has an increased incidence of urinary tract infections. The focus of this study was to determine if the composition of Foley catheter material affects biofilm formation by E. coli in a model system for type 2 diabetes mellitus. Rubber (lubricious-coated), silicon-coated, silver-coated and nitrofurazone-coated catheter segments (5 mm; n = 6) were tested. Catheter segments were added to E. coli ATCC25922 (10 4 CFU/ml, final concentration) in artificial urine alone, or with insulin (40 μU/ml) and/or glucose (0.1%). After incubation (18 h, 37?C, in air and anaerobically) the level of catheter-associated biofilm was determined by crystal violet staining (Abs 550nm ). Statistical analysis was done by ANOVA with post-hoc analysis (Tukey). Neither nitrofurazone-coated nor silver-coated catheters supported the formation of E. coli biofilm, regardless of growth condition tested. In contrast, under aerobic biofilm formation on silicon catheters was significantly higher (p < 0.05) than that on sterile catheter alone. In addition, glucose with insulin induced significantly more biofilm (p < 0.05) than E. coli controls. Biofilm formation was also significantly increased (p < 0.05) under anaerobic conditions on lubricious-coated rubber catheters as compared to sterile catheters. These results may aid in the development of a catheter material that can prevent biofilm formation, or alternatively guide choice of catheter material for individuals shedding insulin in their urine.