Micro-patterned surfaces for reducing bacterial colonization and migration associated with catheter-associated urinary tract infection

Background: The primary device modification strategy for prevention of catheter-associated urinary tract infection (CAUTI) has been to introduce antimicrobial agents onto the catheter material.  However, use of antimicrobial agents can lead to antimicrobial resistance that makes infections difficult to treat. This study presents a unique non-kill, physical surface modification for inhibiting bacterial colonization. This novel biomimetic micro-pattern has demonstrated reduced colonization for several species of microorganisms in vitro.

Objective: The aim was to evaluate in vitro the efficacy of a micro-pattern surface modification in preventing bacterial colonization and migration of a uropathogenic Escherichia coli in the context of silicone Foley catheter application.

Methods: Flat coupons and tubes with and without the micro-pattern were fabricated in silicone. Three variations of the micro-pattern were compared in the colonization assay. Coupons were inoculated with ~10⁶ CFU/ml E. coli in tryptic soy broth (TSB) or artificial urine (AU) and incubated at 37˚C for up to 7 days. Attached cells were enumerated to obtain E. coli colony forming unit (CFU) counts and SEM micrographs of coupons were analyzed for bacterial area coverage.

Additionally, 16 French silicone tube segments were tested in an in vitro migration model to measure the effect of externally patterned tubes for inhibiting migration compared to smooth tubes. Tubes were plugged to test migration on the external surface only, and inoculated at one end with a suspension of E. coli in TSB. Thereafter, tubes were examined at scheduled time-points to determine whether migration had occurred.

 Results: Reduction in E. coli colonization ranged from 38% to 58% on micro-patterned silicone coupons compared to smooth surface, when assessed via enumeration of E. coli CFUs on surfaces and via image analysis of SEM micrographs (Figure 1). Significant reduction in incidence of migration was demonstrated for E. coli, with migration occurring over 27% of smooth tubes vs. only 5% of micro-patterned tubes with a pattern orientation transverse to the direction of migration, yielding 81% reduction in incidence of migration.

Conclusions: The physical surface modification afforded by the micro-patterned texture inhibits the colonization and migration of uropathogenic E. coli in vitro. The results of this study raise the potential for reducing rate of bacteriuria and CAUTI without the use of antimicrobial agents.

Figure 1. Compiled percent reductions comparing micro-patterned surfaces to smooth surfaces for data from all micro-pattern types at various time-points for both growth media. Migration was quantified with a different protocol compared to the other measurement methods; result shown is for the transverse feature orientation. Error bars represent standard error of the mean.