CAUTI are responsible for 20% of episodes of healthcare associated bacteremia in acute care facilities and >50% in long term care facilities.4 Due to these pervasive infections and shortcomings with current treatment and prevention measures, various strategies have been proposed to alleviate this healthcare burden. CAUTI ensues following microbial contamination of the catheter surface. Infection becomes persistent once biofilm formation arises, shielding the pathogens from host immune responses, antibiotics, and antimicrobial agents.5 Several approaches have been taken to modify urinary catheters and materials in efforts to reduce microbial contamination. Antifouling agents on the catheter surface seek to reduce bacterial attachment via steric or electrostatic hindrance.
Catheters coated or infused with biocidal agents can kill pathogens on contact or by elution from the catheter surface. Another strategy to prevent CAUTIs is “bacterial interference”. In contrast to altering the catheter material, “bacterial interference” utilizes living biological agents to compete against uropathogens. Unfortunately, past attempts with commensal strains of E. coli showed limited effectiveness. We became interested in the idea of bacterial interference in CAUTI because of our work developing new probiotic delivery devices to compete against dysbiotic bacteria in the vagina.6-8 For vaginal delivery we had been using different species of Lactobacillus because they are the most common and abundant vaginal bacteria associated with healthy outcomes. Lactobacillus can also be present in the urinary tract where it has been suggested that it may be protective by warding off invading uropathogens. Probiotic Lactobacillus has a long history of safety and in vitro studies have demonstrated the efficacy of several strains against a wide range of uropathogens. Therefore, we reasoned that Lactobacillus would be ideal for “bacterial interference” catheters.
When choosing our design, we turned to 3D bioprinting for several reasons. First, we thought that incorporation of the probiotic into the material itself would give the interference strain a better chance of maintaining an evenly distributed association with the catheter than would dip-coating catheter tubing with the probiotic. Second, 3D printing offers a new method to design catheters with multiple controls that can be optimized to meet the design requirements for custom outcomes. For example, modulating the inner diameter or the tip inlet area to inner lumen area ratio can support different flow rates,9 which could influence bacterial adhesion on the catheter surface. From printing speed and infill density per layer to the printing thickness of each layer, such controls are attuned contingent on the biomaterial utilized and influence mechanical strength.10,11 With high accuracy and resolution, 3D printing can adhere to precise dimensions to elicit a specific behavior of release that is influenced by the surface area-to-volume ratio when biological agents are incorporated into the inks.12 We designed bioprints, composed of a two-part silicone system with a 10:1 mixing ratio and cured at 50°C, to mimic 12 Fr Foley female catheter tubing.13 The formulated bioprint containing L. rhamnosus showed minimal degradation (<2%) and swelling of the outer diameter was <3% when exposed to artificial urine media.
Our previous study demonstrated the ability to incorporate living L. rhamnosus into 3D bioprints and to recover viable bacteria under static conditions in vitro with concentrations >107 CFU/mg after 48 hr.13 Most encouraging was that the L. rhamnosus bioprints were effective at limiting catheter infection by uropathogenic Escherichia coli (UPEC) in vitro (complete eradication after 48 hr in prevention assay).13 The probiotic L. rhamnosus bacteria proliferated and formed a biofilm, taking up space on the surface of the bioprint, and released lactic acid (45 mg of L-lactic acid and 9 mg of D-lactic acid per mg bioprint cumulatively by 14 days) and hydrogen peroxide (>0.1 mM daily).13 Thus, this new probiotic catheter provided an ideal “two-hit punch” that inhibits uropathogens by two different and complementary mechanisms. In our most recent study, we extended our work to demonstrate that 3D-bioprints retain viability and release of probiotics under flow conditions in vitro and in a mouse model of indwelling urinary catheterization.14 Next, we plan to determine the efficacy of 3D bioprints in a preclinical mouse model of CAUTI and to begin fabricating full catheter prototypes that incorporate probiotic bioprints. Building upon work targeting vaginal microbiome dysbiosis, we also plan to engage in mathematical modeling and computational analysis to explore optimal designs and therapeutic strategies.15 Ultimately, we hope that probiotic urinary catheters will be successful at reducing the healthcare burden of CAUTI and provide relief to patients suffering from these often complicated and life-threatening infections.
Written by:
- Anthony J. Kyser, Department of Bioengineering, University of Louisville Speed School of Engineering, Louisville, KY
- Hermann B. Frieboes, Department of Bioengineering, Department of Pharmacology and Toxicology, University of Louisville Speed School of Engineering, Center for Predictive Medicine, Brown Cancer Center, University of Louisville, Louisville, KY, USA.
- Nicole M. Gilbert, Department of Pediatrics, Division of Infectious Diseases, Department of Molecular Microbiology, Department of Obstetrics and Gynecology, Center for Women's Infectious Disease Research, Washington University School of Medicine, St. Louis, MO
- Gray M. Reducing catheter-associated urinary tract infection in the critical care unit. AACN Adv Crit Care. 2010;21(3):247-257.
- Flores-Mireles AL, Walker JN, Caparon M, Hultgren SJ. Urinary tract infections: epidemiology, mechanisms of infection and treatment options. Nature Reviews Microbiology. 2015;13(5):269-284.
- Foxman B. The epidemiology of urinary tract infection. Nat Rev Urol. 2010;7(12):653-660.
- Nicolle LE. Catheter associated urinary tract infections. Antimicrob Resist Infect Control. 2014;3:23.
- Guiton PS, Hung CS, Hancock LE, Caparon MG, Hultgren SJ. Enterococcal biofilm formation and virulence in an optimized murine model of foreign body-associated urinary tract infections. Infect Immun. 2010;78(10):4166-4175.
- Minooei F, Gilbert NM, Zhang L, et al. Rapid-dissolving electrospun nanofibers for intra-vaginal antibiotic or probiotic delivery. Eur J Pharm Biopharm. 2023;190:81-93.
- Minooei F, Kanukunta AR, Mahmoud MY, et al. Mesh and layered electrospun fiber architectures as vehicles for Lactobacillus acidophilus and Lactobacillus crispatus intended for vaginal delivery. Biomater Adv. 2023;154:213614.
- Mahmoud MY, Wesley M, Kyser A, et al. Lactobacillus crispatus-loaded electrospun fibers yield viable and metabolically active bacteria that kill Gardnerella in vitro. Eur J Pharm Biopharm. 2023;187:68-75.
- Stewart CA, Yamaguchi E, Teixeira Vaz J, Gaver DP, 3rd, Ortenberg J. Flow characteristics of urethral catheters of the same caliber vary between manufacturers. J Pediatr Urol. 2017;13(4):377.e371-377.e376.
- Farmer ZL, Utomo E, Domínguez-Robles J, et al. 3D printed estradiol-eluting urogynecological mesh implants: Influence of material and mesh geometry on their mechanical properties. Int J Pharm. 2021;593:120145.
- Janusziewicz R, Mecham SJ, Olson KR, Benhabbour SR. Design and Characterization of a Novel Series of Geometrically Complex Intravaginal Rings with Digital Light Synthesis. Adv Mater Technol. 2020;5(8).
- Kyser AJ, Fotouh B, Mahmoud MY, Frieboes HB. Rising role of 3D-printing in delivery of therapeutics for infectious disease. J Control Release. 2024.
- Kyser AJ, Mahmoud MY, Johnson NT, et al. Development and Characterization of Lactobacillus rhamnosus-Containing Bioprints for Application to Catheter-Associated Urinary Tract Infections. ACS Biomater Sci Eng. 2023;9(7):4277-4287.
- Kyser AJ, Greiner A, Harris V, Patel R, Frieboes HB, Gilbert NM. 3D-Bioprinted Urinary Catheters Enable Sustained Probiotic Recovery Under Flow and Improve Bladder Colonization In Vivo. Probiotics Antimicrob Proteins. 2025.
- Rai V, Kyser AJ, Goodin DA, Mahmoud MY, Steinbach-Rankins JM, Frieboes HB. Computational Modeling of Probiotic Recovery from 3D-Bioprinted Scaffolds for Localized Vaginal Application. Ann 3D Print Med. 2023;11.