Catheter-associated urinary tract infections (CAUTIs) are a significant challenge for intermittent catheter (ICs) users and are thought to be driven by bacterial displacement from the distal urethra to the bladder upon catheter insertion [1-3]. There are a range of commercially available ICs with features that aim to reduce the risk of CAUTIs, including closed-systems, “no touch” sleeves, and protective insertion tips [4]. Other IC features include pre-lubrication that help reduce friction/urethral trauma during catheterisation; however, there are lack of studies investigating the role lubricants play in bacterial displacement and CAUTIs. Using a modified method by Cortese et al. [1], we assessed the effectiveness of two female and male ICs that have been pre-lubricated either by gel- or water- based lubricants in reducing bacterial displacement along a simulated urethra. The study hypothesis was that the use of different IC lubrication can affect bacterial displacement from the meatus/distal urethra, thereby impacting the number of bacteria that can enter the bladder.

Four ICs (CH12) with gel-based (gel-based female [GBF] and gel-based male [GBM], Cure Medical, Henderson, NV, USA) or water-based (water-based male [WBM] and water-based female [WBF], Coloplast Ltd, Orton, Peterborough, UK) lubricants were evaluated. 
Urethra agar channels (UACs) were prepared by dispensing selective molten agar (Harlequin Tryptone Bile Glucuronide agar for E. coli NCIMB 14067 [colonies appear blue-green] and Harlequin vancomycin-resistant Enterococcus chromogenic agar for E. faecalis NCTC 12201 [colonies appear dark green]) into a 30 ml universal container with a 4 mm stainless steel rod. Once the agar had set, the steel rod was removed and the first 1 cm of the UAC was inoculated with the challenge organism before insertion of the test IC. After two minutes (simulating approximate urination time), the IC was removed and the UAC were processed in one of two ways: total viable counts (TVCs) or visual displacement images. TVCs were performed by aseptically cutting the UAC into 1 cm sections starting at the insertion entry, before enumeration of the first (where inoculation has occurred and represents the meatus/distal urethra), third, fifth and seventh (simulated bladder) sections. Numbers of bacteria in section 7 were compared using a Student T-Test to establish significant differences. For visual displacement images, the UACs were incubated at 35±3°C for at least 48 hours, then images were taken of the growth observed along the channels. Five replicates per catheter were performed for each assessment. A no-catheter bacterial growth control was also performed.
Additionally, confocal laser scanning microscopy (CLSM) was performed on the test ICs (n=3 catheters in three catheter UAC contact areas) using fluorescently tagged E. coli to establish where on the catheter the bacteria had been transferred during the testing (i.e., from the contaminated section, the simulated distal urethra).

Visual displacement images show that the challenge organisms remained at the inoculation site of the UAC (first 1 cm) for the no-catheter control (Figure 1). For all test catheters, E. coli was displaced along the UAC to a lesser extent than E. faecalis. Visually, the GBF and GBM ICs displaced fewer bacteria to section 7 of the UAC compared to the WBF and WBM ICs, with the difference being more pronounced with E. coli. TVCs were comparable to the visual images, which showed a consistent downward trend in E. coli (Figure 2) along the UAC for the GBF and GBM ICs, which had displaced fewer bacteria at section 7 compared to the WBM (p=0.0004) and WBF (p=0.0662) catheters, respectively. This difference was also observed for E. faecalis for the WBM (p=0.0022) and WBF (p=0.0003) catheters. Notably, levels of E. coli were undetectable (GBM) or nearly undetectable (GBF) at section 7 for the gel-based lubricant ICs, which was not observed for the other tested catheters. These undetectable levels were not achieved against E. faecalis by any of the ICs tested. CLSM imaging showed the presence of bacteria on the catheter. While all ICs had bacteria present on the surface, most of the bacteria were observed within the gel-based lubricant for the GBF and GBM ICs. In contrast, most of the bacteria were observed in the water of the WBF and WBM ICs.

The ICs with gel-based lubricants (GBF and GBM) displaced fewer bacteria from the distal urethra to the bladder compared to ICs with water-based lubricants (WBF and WBM). The differences in bacterial displacement may be attributed to the differences in lubricant composition and viscosity (gel- versus water-based) which may affect the motility of bacteria. It was observed that the bacteria transferred to the catheter and were also predominantly found within the lubricant, supporting this hypothesis.

Using a validated in vitro urethral agar channel model, we show that ICs with gel-based lubricants displaced fewer bacteria from the distal urethra to the bladder compared to ICs with water-based lubricants. These findings suggest that lubricant type and/or viscosity may play a role in bacterial transfer from a contaminated meatus along the urethra, with the increased viscosity of gel-based lubricants potentially trapping the bacteria to reduce its transfer. Further future research will be performed to establish if this is the case.

Cortese, Y.J., et al., Pathogen displacement during intermittent catheter insertion: a novel in vitro  urethra model. Journal of Applied Microbiology, 2019. 128(4): p. 1191-1200.
Trautner, B.W. and R.O. Darouiche, Catheter-associated infections: pathogenesis affects prevention. Arch Intern Med, 2004. 164(8): p. 842-50.
Barford, J.M.T. and A.R.M. Coates, The pathogenesis of catheter-associated urinary tract infection. Journal of Infection Prevention, 2009. 10(2): p. 50-56

Continence 12S (2024) 101590
DOI: 10.1016/j.cont.2024.101590