Biomaterials Used in Urology: Current Issues of Biocompatibility, Infection, and Encrustation*

Abstract

This review focuses on the biomaterials used in urology, in particular, the properties of urethral catheters and ureteral stents currently being used in clinical practice. The importance of biomaterial type, biocompatibility, and encrustations are discussed and explained. Current management of bacterial infection and the importance of biofilms are presented, with recommendations based on published information.

Role of biofilm in catheter-associated urinary tract infection☆

“…For example, several studies reported that gram-negative bacteria adhered less to siliconized rubber than to other catheter materials. 4,72 Fig 1 shows a confocal microscopy image of a siliconized latex surface that had been incubated with E coli in broth for only 48 hours; a thick biofilm is clearly visible. Impregnating urinary catheters with antimicrobial agents, such as silver ions or nitrofurazone, 73 has also been attempted.…”

“…2 A formal definition of biofilm includes 3 components: (1) adherence of the microorganisms, either to a surface or to each other; (2) a change in gene expression resulting in a different phenotype from the planktonic state; and (3) an extracellular matrix composed of host components and secreted bacterial products. 3,4 A functional definition of biofilm also includes the fact that biofilm results in chronic, persistent infections that are difficult to eradicate with antimicrobial therapy. 5 The relevance of biofilm to catheter-associated urinary tract infection (UTI) (CAU-TI) is that a foreign body, such as an indwelling urethral catheter, connecting a normally sterile, hydrated body site to the outside world will inevitably become colonized with microorganisms.…”

“…5 The relevance of biofilm to catheter-associated urinary tract infection (UTI) (CAU-TI) is that a foreign body, such as an indwelling urethral catheter, connecting a normally sterile, hydrated body site to the outside world will inevitably become colonized with microorganisms. 4 Thus, the central character in the story of CAUTI is really the biofilm on the urinary catheter. …”

“…The first step in biofilm formation on a urinary catheter is deposition of a conditioning film of host urinary components, including proteins, electrolytes, and other organic molecules. 4 This conditioning film can transform the surface of the urinary catheter and neutralize any antiadhesive properties. 3 Free-swimming bacteria attach to the surface through hydrophobic and electrostatic interactions and through the use of flagella.…”

“…3 Free-swimming bacteria attach to the surface through hydrophobic and electrostatic interactions and through the use of flagella. 4,10 Attachment is followed by cell division, recruitment of additional planktonic bacteria, and secretion of extracellular matrix. Cell-to-cell signaling directs the formation of loosely packed 3-dimensional structures with fluid channels between them to permit exchange of nutrients and wastes.…”