The bacterial displacement test: an in vitro microbiological test for the evaluation of intermittent catheters and urinary tract infection

AIMS

Intermittent catheters (ICs) are commonly used in bladder management, but catheter-associated urinary tract infections (CAUTIs) remain challenging. Insertion tips may reduce the risk of CAUTIs by minimizing bacterial transfer along the urinary tract. However, there are few laboratory tests to evaluate such technologies. We describe the use of an adapted in vitro urethra agar model to assess bacterial displacement by ICs.

METHODS AND RESULTS

Simulated urethra agar channels (UACs) were prepared with catheter-specific sized channels in selective media specific to the challenge organisms. UACs were inoculated with Escherichia coli and Enterococcus faecalis before insertion of ICs, and enumeration of UAC sections was performed following insertion. Four ICs were evaluated: Cure Catheter® Closed System (CCS), VaPro Plus Pocket™, Bard® Touchless® Plus, and SpeediCath® Flex Set. CCS demonstrated significantly reduced bacterial displacement along the UACs compared to the other ICs and was also the only IC with undetectable levels of bacteria toward the end of the UAC (representing the proximal urethra).

CONCLUSION

The bacterial displacement test demonstrated significant differences in bacterial transfer between the test ICs with insertion tips, which may reflect their different designs. This method is useful for evaluating CAUTI prevention technology and may help guide future technology innovations.

Tackling catheter-associated urinary tract infections with next-generation antimicrobial technologies

Urinary catheters and other medical devices associated with the urinary tract such as stents are major contributors to nosocomial urinary tract infections (UTIs) as they provide an access path for pathogens to enter the bladder. Considering that catheter-associated urinary tract infections (CAUTIs) account for approximately 75% of UTIs and that UTIs represent the most common type of healthcare-associated infections, novel anti-infective device technologies are urgently required. The rapid rise of antimicrobial resistance in the context of CAUTIs further highlights the importance of such preventative strategies. In this review, the risk factors for pathogen colonization in the urinary tract are dissected, taking into account the nature and mechanistics of this unique environment. Moreover, the most promising next-generation preventative strategies are critically assessed, focusing in particular on anti-infective surface coatings. Finally, emerging approaches in this field and their likely clinical impact are examined.

A strategy to control colonization of pathogens: embedding of lactic acid bacteria on the surface of urinary catheter

Indwelling urinary catheterization is one of the major causes of urinary tract infection (UTI) in hospitalized patients worldwide. A catheter serves as a surface for the colonization and formation of biofilm by UTI-related pathogenic bacteria. To combat the biofilm formation on its surface, several strategies have already been employed such as coating it with antibiofilm and antimicrobial compounds. For instance, the application of lactic acid bacteria (LAB) offers a potential strategy for the treatment of biofilm formation on the surface of the urinary catheter due to its ability to kill the pathogenic bacteria. The killing of pathogenic bacteria by LAB occurs via the production of antimicrobial compounds such as lactic acid, bacteriocin, and hydrogen peroxide. LAB also displays a competitive exclusion mechanism to prevent the adhesion of pathogens on the surfaces. Hence, LAB has been extensively applied as a bacteriotherapy to combat infectious diseases. Several strategies have been employed to attach LAB to a surface, but its easy detachment during long time exposure becomes one of the drawbacks in its application. Here, we have proposed a novel strategy for its adhesion on the surface of the urinary catheter with the utilization of mannose-specific adhesin (Msa) protein in a way similar as uropathogenic bacteria interacts between Msa present on the tip of the type I fimbriae/pilus and the mannose moieties on the host epithelial cell surfaces. KEY POINTS: • Urinary tract infection (UTI) is one of the common hospital-acquired infections, which is associated with the application of an indwelling urinary catheter. • Based on the competitive exclusions properties of LAB, attachment of the LAB on the catheter surface would be a promising approach to control the formation of pathogenic biofilm. • The strategy employed for the adhesion of LAB is via a covalent interaction of its mannose-specific adhesin (Msa) protein to the mannose residues grafted on the catheter surface.

Pilot Ex Vivo and In Vitro Evaluation of a Novel Foley Catheter with Antimicrobial Periurethral Irrigation for Prevention of Extraluminal Biofilm Colonization Leading to Catheter-Associated Urinary Tract Infections (CAUTIs)

CAUTI remains a serious healthcare issue for incontinent patients whose urine drainage is managed by catheters. A novel double-balloon Foley catheter was developed which was capable of irrigating the extraluminal catheter surfaces within the periurethral space between the urethral-bladder junction and meatus. The catheter has a retention cuff that is inflated to secure the catheter in the bladder and a novel irrigation cuff proximal to the urethral-bladder junction capable of providing periurethral irrigation from the urethral-bladder junction to the meatus. Uniform periurethral irrigation was demonstrated in an ex vivo porcine model by adding a dye to the antimicrobial urethral irrigation solution. An in vitro biofilm colonization model was adapted to study the ability of periurethral irrigation with a newly developed antimicrobial combination consisting of polygalacturonic acid + caprylic acid (PG + CAP) to prevent axial colonization of the extraluminal urethral indwelling catheter shaft by common uropathogens. The extraluminal surface of control catheters that were not irrigated formed biofilms along the entire axial urethral tract after 24 hours. Significant (p < 0.001) inhibition of colonization was seen against multidrug-resistant Pseudomonas aeruginosa (PA), carbapenem-resistant Escherichia coli (EC), and carbapenem-resistant Klebsiella pneumoniae (KB). For other common uropathogens including Candida albicans (CA), Proteus mirabilis (PR), and Enterococcus faecalis (EF), a first irrigation treatment completely inhibited colonization of half of the indwelling catheter closest to the bladder and a second treatment largely disinfected the remaining intraurethral portion of the catheter towards the meatus. The novel Foley catheter and PG + CAP antimicrobial irrigant prevented biofilm colonization in an in vitro CAUTI model and merits further testing in an in vivo CAUTI prevention model.

Vitamin C in the Presence of Sub-Inhibitory Concentration of Aminoglycosides and Fluoroquinolones Alters Proteus mirabilis Biofilm Inhibitory Rate

Vitamin C has antimicrobial activity and is often used as an oral supplement accompanying antibiotic treatment in urinary tract infections (UTI). Proteus mirabilis is the third common species responsible for UTIs that are mostly treated with fluoroquinolones or aminoglycosides. Treatment of the UTI caused by P. mirabilis is problematic due to the ability to form biofilm on the urinary catheters. The aim of the study was to evaluate the influence of ascorbic acid in combination with antibiotics on P. mirabilis abilities to form biofilm. The susceptibility of P. mirabilis reference strain ATCC^® 29906™ and four clinical strains isolated from the urine samples of patients with urinary catheter were evaluated according to EUCAST recommendations. The influence of ascorbic acid (0.4 mg × mL⁻¹) in combination with antibiotics on biofilm formation was evaluated spectrophotometrically. Aminoglycosides at sub-inhibitory concentrations more successfully limited biofilm formation by P. mirabilis strains without ascorbic acid addition. Inhibition rate differences at the lowest concentrations of gentamicin and amikacin were statistically significant (p ≤ 0.05). Ascorbic acid addition to the culture medium limited the inhibitory effect of fluoroquinolones, facilitating biofilm formation by P. mirabilis strains. The addition of ascorbic acid during aminoglycosides therapy may disturb treatment of urinary tract infections related to the presence of P. mirabilis biofilm.

Evaluating Efficacy of Antimicrobial and Antifouling Materials for Urinary Tract Medical Devices: Challenges and Recommendations

In Europe, the mean incidence of urinary tract infections in intensive care units is 1.1 per 1000 patient-days. Of these cases, catheter-associated urinary tract infections (CAUTI) account for 98%. In total, CAUTI in hospitals is estimated to give additional health-care costs of £1-2.5 billion in the United Kingdom alone. This is in sharp contrast to the low cost of urinary catheters and emphasizes the need for innovative products that reduce the incidence rate of CAUTI. Ureteral stents and other urinary-tract devices suffer similar problems. Antimicrobial strategies are being developed, however, the evaluation of their efficacy is very challenging. This review aims to provide considerations and recommendations covering all relevant aspects of antimicrobial material testing, including surface characterization, biocompatibility, cytotoxicity, in vitro and in vivo tests, microbial strain selection, and hydrodynamic conditions, all in the perspective of complying to the complex pathology of device-associated urinary tract infection. The recommendations should be on the basis of standard assays to be developed which would enable comparisons of results obtained in different research labs both in industry and in academia, as well as provide industry and academia with tools to assess the antimicrobial properties for urinary tract devices in a reliable way.

Incidence and Risk Factors for Urinary Tract Infection in an Elder Home Care Population in Taiwan: A Retrospective Cohort Study

Urinary tract infection (UTI) is a common infection worldwide. Numerous studies have demonstrated risk factors for UTI in facilities and communities. In this study, we aimed to identify risk factors for UTI in home care patients. Patients who received home care for at least three months in 2017 were included. A UTI episode was defined by admission for UTI treatment, and/or a visit to an outpatient department for UTI and receiving antibiotic prescription. A total of 598 patients aged 81.9 years were included. Overall 47% (281) had at least one UTI episode. After analysis, urinary catheter indwelling was the most important risk factor (odds ratio (OR), 3.21). Underlying diseases (coronary artery disease (CAD), chronic kidney disease (CKD), diabetes mellitus (DM)) were related to UTI with OR ranging from 1.46 to 1.79. Higher Alb (albumin) (OR 0.68) and Hb (hemoglobin) (OR 0.91) were inversely related to UTI. Polypharmacy (OR 1.84) and lower Barthel index scores (OR 1.62) were also related to UTI by different degrees. In conclusion, apart from the unmodifiable factors, avoiding prolonged urinary catheter placement, unnecessary prescriptions, and keeping good nutritional status may help to prevent UTI in home care patients.

Azithromycin-Ciprofloxacin-Impregnated Urinary Catheters Avert Bacterial Colonization, Biofilm Formation, and Inflammation in a Murine Model of Foreign-Body-Associated Urinary Tract Infections Caused by Pseudomonas aeruginosa

Pseudomonas aeruginosa is a multifaceted pathogen causing a variety of biofilm-mediated infections, including catheter-associated urinary tract infections (CAUTIs). The high prevalence of CAUTIs in hospitals, their clinical manifestations, such as urethritis, cystitis, pyelonephritis, meningitis, urosepsis, and death, and the associated economic challenges underscore the need for management of these infections. Biomaterial modification of urinary catheters with two drugs seems an interesting approach to combat CAUTIs by inhibiting biofilm. Previously, we demonstrated the in vitro efficacy of urinary catheters impregnated with azithromycin (AZM) and ciprofloxacin (CIP) against P. aeruginosa Here, we report how these coated catheters impact the course of CAUTI induced by P. aeruginosa in a murine model. CAUTI was established in female LACA mice with uncoated or AZM-CIP-coated silicone implants in the bladder, followed by transurethral inoculation of 10⁸ CFU/ml of biofilm cells of P. aeruginosa PAO1. AZM-CIP-coated implants (i) prevented biofilm formation on the implant's surface (P ≤ 0.01), (ii) restricted bacterial colonization in the bladder and kidney (P < 0.0001), (iii) averted bacteriuria (P < 0.0001), and (iv) exhibited no major histopathological changes for 28 days in comparison to uncoated implants, which showed persistent CAUTI. Antibiotic implants also overcame implant-mediated inflammation, as characterized by trivial levels of inflammatory markers such as malondialdehyde (P < 0.001), myeloperoxidase (P < 0.05), reactive oxygen species (P ≤ 0.001), and reactive nitrogen intermediates (P < 0.01) in comparison to those in uncoated implants. Further, AZM-CIP-coated implants showed immunomodulation by manipulating the release of inflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and IL-10 to the benefit of the host. Overall, the study demonstrates long-term in vivo effectiveness of AZM-CIP-impregnated catheters, which may possibly be a key to success in preventing CAUTIs.