In Situ Microscopy Imaging of Biofilm Formation on Mannoside-modified Silicone Surfaces

The prevention of catheter-associated urinary tract infection (CAUTI) over long-term usage of urinary catheters remains a great challenge. Antibiotic resistance is an inevitable outcome of urinary catheterization and is closely associated with CAUTIs. An alternative approach is needed to combine broad-spectrum antibiotics, improved diagnostic, and surveillance techniques to prevent bacterial attachment to the catheter. Bacterial interference is a non-antibiotic-based strategy for CAUTI prevention using benign bacteria as living guards against pathogenic colonization on catheter surfaces. We proposed to pre-establish benign bacterial biofilm on the catheter surface to enhance the effectiveness of the bacterial interference strategy against urinary pathogenic colonization. Escherichia coli 83972 as a prophylactic agent has been utilized in several pilot-scale clinical studies for the prevention of CAUTI. The mannoside-presenting surfaces promote early-stage adhesion of an engineered strain of E. coli 83972 expressing type 1 fimbriae (denoted as fim+ E. coli 83972) terminated with FimH adhesin that binds mannoside derivatives. In this study, we modified the silicone surface with a series of mannoside derivatives and incubated the fim+ E. coli 83972 under both static and flow conditions. We showed that the bacterial adhesion and biofilm formation were directly related to the mannoside binding affinity. To systematically study the effect of the immobilized mannoside binding affinities on the biofilm formation at the early stage by fim+ E. coli 83972, we constructed a device allowing for in situ microscopy imaging with z-stack of the biofilm formation on the mannoside-modified silicone surfaces. The result of the quantitative analysis of the imaging data showed that the first layer of bacteria attached on a stronger binding affinity mannoside surface on silicone not only exhibited a higher coverage on the surface but also promoted the growth and stability of the upper layers. Finally, we showed that the silicone catheter surfaces coated with urinary proteins enabled the binding of wild-type E. coli 83972 without type I fimbriae under both static and flow conditions.