The Impact of Silver-coating of a Urinary Catheter on Bacterial Adherence, Biofilm Formation, Bacteriuria, Positive Culture, UTI, and the Association of Urovirulence Factors with Biofilm Formation in Escherichia Coli

Catheter-associated bacteriuria (CAB) and urinary tract infection (CAUTI) are important clinical problems in catheterized humans and dogs. A variety of methods to reduce CAB and CAUTI have been investigated, and in humans, silver coating of urinary catheters has been shown to reduce CAB and CAUTI in randomized prospective clinical trials. The objectives of the studies reported in this thesis are to evaluate adherence of clinical isolates of E. coli to a silver coated urinary catheter, evaluate the potential association of E. coli urovirulence factors to E. coli biofilm formation in vitro, and assess the efficacy of the silver coated urinary catheter in canine patients in a randomized clinical trial. Clinical isolates of E. coli were incubated with silver coated and standard (uncoated) urinary catheters. Significantly fewer bacteria were adhered to the silver coated urinary catheter at 24, 48, and 72 hours of incubation, and following subjective analysis using SEM analysis. Clinical isolates of E. coli were investigated for the presence of urovirulence factors and the association between these urovirulence factors and biofilm formation in vitro. Prevalence of urovirulence factors were similar to what has been reported, and cnf1 was associated with biofilm formation. A prospective, randomized, controlled clinical trial was performed to assess the ability of silver coated urinary catheters to reduce CAB and CAUTI in hospitalized dogs requiring catheterization. Catheterized dogs were assessed for bacteriuria, positive culture, and urinary tract infections following catheterization. No significant differences were noted between groups in regard to CAB, CAUTI, and positive culture incidence in the two groups. We have shown that clinical E. coli isolates adhered less to a silver coated urinary catheter compared to a non-silver coated urinary catheter in vitro, and that cnf1 is associated with in vitro biofilm formation. We were unable to detect a significant difference in CAUTI or CAB in hospitalized dogs, most likely due to low study numbers. Further clinical studies are required to determine the utility of these catheters in hospitalized patients.