Pathogen displacement during intermittent catheter insertion: a novel in vitro urethra model

Abstract

Aim To develop a novel in vitro urethra model and use it to determine if insertion of an intermittent urinary catheter (IC) displaces pathogenic bacteria from the urethral meatus along the urethra. Methods Displacement of microbial growth after catheter insertion was assessed using a novel in vitro urethra model. The in vitro urethra model utilized chromogenic agar and was inoculated with bacteria at one side of the artificial urethra channel, to act as a contaminated urethral meatus, before an IC was inserted into the channel. Three ICs types were used to validate the in vitro urethra model and methodology. Results When compared to the bacterial growth control, a significant difference in bacterial growth was found after insertion of the uncoated (P ≤ 0·001) and hydrophilic coated (P ≤ 0·009) catheters; no significant difference when a prototype catheter was inserted into the in vitro urethra model with either bacterial species tested (P ≥ 0·423). Conclusion The results presented support the hypothesis that a single catheter insertion can initiate a catheter‐associated urinary tract infection. Significance and Impact of the Study The in vitro urethra model and associated methodology were found to be reliable and reproducible (P ≥ 0·265) providing new research tool for the development and validation of emerging technologies in urological healthcare.

Microbial Transfer by Intermittent Catheters

“…Rather than attempting to reproduce the techniques for clean or sterile catheterization used in the clinical setting, we designed these experiments using a worst-case scenario that combined inoculation of both the gloved hands of the operator and meatus with an artificially high microbial challenge (eg, 10 9 and 10 7 , respectively). The meatus was selected for inoculation as it is widely known that the first 15 mm of the urethra (inclusive of the meatus) is not sterile, and catheter insertion risks transferring pathogenic microorganisms into the bladder vesicle 5…”

“…As the catheter is advanced into the anatomical model, various predefined catheter segments were isolated into sample bottles for enumeration (see step 3, Figure 1). These segments were selected based on the catheterization process and the average length of catheter tubing that advanced through the urethra and into the bladder 5. Specifically, the first two 2-inch segments of the catheter (C1 and C2 or US_C1 and US_C2 for unsleeved catheters) were placed into wide-mouthed polypropylene bottles containing 50-mL sterile 0.9% saline.…”

“…22 Additionally, certain design features have been added to ICs to help minimize contamination during insertion such as a ring tip, a protective introducer tip, protective sleeve, handling sleeve, or a gripping mechanism. 27 Modeling UTIs in vitro via catheter contamination has been reported previously including a catheterized bladder model 28,29 and urinary tract model 5,30 for indwelling catheter applications, as well as models for intermittent catheter insertion. 30 This article reports findings from a novel in vitro model of microbial transfer via contaminated, gloved hands with 3 archetypal uropathogenic microbes during simulated intermittent catheter insertion.…”

“…Uropathogenic microorganisms use several mechanisms to infect the urinary tract; one such mechanism is introduction of microbes into the urinary tract by a foreign object such as a catheter resulting in catheter-associated UTI (CAUTI), a complicated UTI. There are several ways that urinary catheters may be exposed to microbes during normal use: examples are touch transfer from contaminated surfaces prior to insertion into the urethra (eg, the user's hands), and transfer from a contaminated meatus during insertion 5. Microbial attachment to the catheter surface is facilitated via expression of adhesion proteins; these proteins are also responsible for attachment to the urothelium, thereby initiating microbial colonization and infection 6…”

A novel in vitro urethra model to demonstrate bacterial displacement during urinary catheter insertion

“…It is envisaged that this model will be a useful tool in the future development of urinary catheters and other devices that can prevent or eliminate the movement of bacteria during medical device insertion. This model and methodology has been recently published in the Journal of Applied Microbiology [5].…”