In Vitro Effects of a Novel Coating Agent on Bacterial Biofilm Development on Ureteral Stents

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

Medical devices such as venous catheters (VCs) and urinary catheters (UCs) are widely used in the hospital setting. However, the implantation of these devices is often accompanied by complications. About 60 to 70% of nosocomial infections (NIs) are linked to biofilms. The main complication is the ability of microorganisms to adhere to surfaces and form biofilms which protect them and help them to persist in the host. Indeed, by crossing the skin barrier, the insertion of VC inevitably allows skin flora or accidental environmental contaminants to access the underlying tissues and cause fatal complications like bloodstream infections (BSIs). In fact, 80,000 central venous catheters-BSIs (CVC-BSIs)-mainly occur in intensive care units (ICUs) with a death rate of 12 to 25%. Similarly, catheter-associated urinary tract infections (CA-UTIs) are the most commonlyhospital-acquired infections (HAIs) worldwide.These infections represent up to 40% of NIs.In this review, we present a summary of biofilm formation steps. We provide an overview of two main and important infections in clinical settings linked to medical devices, namely the catheter-asociated bloodstream infections (CA-BSIs) and catheter-associated urinary tract infections (CA-UTIs), and highlight also the most multidrug resistant bacteria implicated in these infections. Furthermore, we draw attention toseveral useful prevention strategies, and advanced antimicrobial and antifouling approaches developed to reduce bacterial colonization on catheter surfaces and the incidence of the catheter-related infections.

Recanalize ureteral stents with focused ultrasound

BACKGROUND

Maintaining ureteral patency is imperative to preventing renal injury and systemic infection. Ureteral stents are small conduits connecting the kidney and the bladder. They have been widely used to treat ureteral obstructions and ureteral leaks. The most problematic and frequent stent-associated complication is stent encrustation. This occurs when mineral crystals (e.g. calcium, oxalate, phosphorus, struvite) are deposited onto the surface and internal lumen of the stent. Encrustation can lead to the obstruction of a stent and increases risk of systemic infection. As a result, ureteral stents need to be replaced typically every 2-3 months.

PURPOSE

In this study, we present a non-invasive, high-intensity focused ultrasound (HIFU)-based technique to recanalize obstructed stents. By taking advantage of the mechanical force produced by a HIFU beam, including acoustic radiation force, acoustic streaming, and cavitation, HIFU can break up encrustations, clearing the stent of obstruction.

METHODS

The ureteral stents for this study were obtained from patients undergoing ureteral stent removal. Under the guidance of ultrasound imaging, the encrustation in the stents were located, and then targeted by HIFU at frequencies of 0.25 and 1 MHz. The duty cycle of HIFU was 10%, and the HIFU burst repetition rate was 1 Hz, while the HIFU amplitude was varied to find the threshold pressure that would displace encrustations. The treatment duration was limited at 2 min (or 120 shots from HIFU). The treatments were carried out in two different orientations (parallel and perpendicular) of the ureteral stent with respect to the HIFU beam. For each setting, five treatments were conducted for a maximum duration of 2 min. During the entire treatment, an ultrasound imaging system was used to monitor the movement of encrustations inside the stent. The peak negative HIFU pressures needed to move the encrustations inside the stent was recorded for quantitative analysis.

RESULTS

Our results demonstrated that at both 0.25 and 1 MHz ultrasound frequencies, obstructed stents could be recanalized. At 0.25 MHz, the needed average peak negative pressure was 0.52 MPa in parallel orientation and 0.42 MPa in perpendicular orientation. At 1 MHz, the needed average peak negative pressure was 1.10 MPa in parallel orientation and 1.15 MPa in perpendicular orientation CONCLUSIONS: This first in-vitro study has demonstrated the feasibility of non-invasive HIFU to recanalize ureteral stents. This technology has a potential to reduce the need for ureteral stent exchange.

All-in-one properties of an anticancer-covered airway stent for the prevention of malignant central airway obstruction

Malignant central airway obstruction (MCAO) resulting from tumor metastasis and compression severely impairs respiration, posing life-threatening risks. To address this, we employed a synergistic modification strategy, combining cisplatin (CIS) and silver nanoparticles (AgNPs). Polycaprolactone (PCL) served as a drug carrier, enabling the preparation of a functional CIS@AgNPs@PCL fiber membrane-covered airway stent via electrospinning. This approach aimed to enhance the patency rate of MCAO. Characterization via ATR-FTIR, scanning electron microscope-energy-dispersive spectroscopy, and transmission electron microscope confirmed successful immobilization of CIS and AgNPs onto the stent surface. CIS@AgNPs@PCL substantially suppressed non-small cell lung cancer cells (A549), causing DNA damage, ultrastructural disruption, and over 50% apoptosis in 48 h. It also displayed potent antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans biofilms. A mouse subcutaneous tumor recurrence model assessed anti-cancer efficacy. CIS@AgNPs@PCL fiber-covered stents significantly inhibited lung cancer tissue and enhanced anti-cancer effects by up-regulating caspase-3 and Bax, while down-regulating Bcl-2. This study's functional airway stent provides a proof-of-concept for an integrated anti-cancer and antibacterial strategy. It promptly restores the lumen, inhibits biofilm formation, prevents tumor progression, and improves postoperative MCAO patency.

A modified biodegradable mesh ureteral stent for treating ureteral stricture disease

Ureteral stricture disease (USD) is a common urologic condition. Patients with ureteral stricture disease may suffer from ipsilateral flank pain, nausea, urinary calculi, infection, and impaired renal function. The treatments of USD include surgery, followed by implantation of the ureteral stent to aid the drainage of the urine. The traditional ureteral stent may sometimes cause urological infection, encrustation, and discomfort. To decrease the complication of the ureteral stent, we modified the structure and material based on the traditional ureteral stent. The traditional nondegradable Double-J shape tubular ureteral stent was turned into the biodegradable mesh ureteral stent. The modified mesh ureteral stent and Double-J ureteral stent were inserted into the ureters of the USD animals, respectively. The results of the gross morphology, serology, urinalysis, histology, microstructure, et al. demonstrated that modified mesh ureteral stent has a favorable ability in supporting the ureter and has no effect on cell proliferation, migration, apoptosis, and cell cycle of the human uroepithelial cells. The mesh ureteral stent could relieve ureter obstruction and can be slowly biodegraded after 3-5 months of implantation without the need for a second surgery to remove the stent. Compared to the Double-J ureteral stent, the modified mesh ureteral stent has a lower rate of urinary tract infection and less encrustation. It is expected to be an alternative treatment approach for USD. However, due to the limited number of animals and clinical data, further study focused on the application value in clinical practice are essential. STATEMENT OF SIGNIFICANCE: This study demonstrates: 1. A modified biodegradable mesh ureteral stent; 2. Without the need for a second surgery to remove the stent; 3. A lower rate of urinary tract infection and less encrustation than a double-J ureteral stent; 4. An alternative treatment approach for USD.

A PEDOT nano-composite for hyperthermia and elimination of urological bacteria

Novel modalities for overcoming recurrent urinary tract infections associated with indwelling urinary catheters are needed, and rapidly induced hyperthermia is one potential solution. PEDOT nanotubes are a class of photothermal particles that can easily be incorporated into silicone to produce thin, uniform coating on medical grade silicone catheters; subsequent laser stimulation therein imparts temperature elevations that can eliminate bacteria and biofilms. PEDOT silicone coatings are stable following thermal sterilization and repeated heating and cooling cycles. Laser stimulation can induce temperature increases of up to 55 °C in 300 s, but only 45 s was needed for ablation of UTI inducing E. coli biofilms in vitro. This work also demonstrates that mild hyperthermia of 50 °C, applied for only 31 s in the presence of antibiotics could eliminate E. coli biofilm as effectively as high temperatures. This work culminates in the evaluation of the PEDOT NTs for photothermal elimination of E. coli in an in vivo model to demonstrate the safety and effectiveness of a photothermal nanocomposite (16 s treatment time) for rapid clearance of E. coli.

Bacterial colonization in three different parts of double J stent

Introduction:

Due to the extensive use of indwelling stents and catheters in urology, bacterial colonization on these materials is a significant cause of infections in this group of patients. This study aims to investigate and compare the bacterial colonization in urine and in the three zones of the double J (DJ) stent.

Methods:

Between August 2019 and May 2020, 67 patients (18–78 years old) who underwent DJ stenting were recruited in the study. Surgeries before stenting included transurethral lithotripsy (TUL), percutaneous nephrolithotomy (PCNL), or diagnostic ureteroscopy. Before stenting, sterile urine samples were collected, and urinary cultures were performed, and the same procedure was done after removal of the DJ stents. DJ stent cultures were also performed.

Results:

61 patients were analyzed. The mean age of all patients was 53 ± 16 years. The mean time of DJ installation in all patients was 27.6 ± 6.7 days (14–43 days). In these three parts of the DJ, 70.5%, 67.2%, and 72.1% of patients were without a colony, respectively. The microorganism distribution is approximately the same in the lower and upperparts, and Escherichia coli has the highest frequency (11.5%). The odds ratio (OR) of contamination was significantly lower in men than in women, but overweight and diabetes were not associated.

Conclusion:

The severity and pattern of bacterial colonization are not significantly different in the proximal, distal, and middle parts of the DJ stent.

New Stent Technologies

Ureteral stents are an indispensable part of any (endo-) urologic practice. Despite the widely demonstrated advantages of stents, they also carry a considerable risk of side effects and complications, such as urinary symptoms, pain, hematuria, decreased quality of life, stent-related infection, and encrustation. Multiple pathways in preventing or mitigating these side effects and complications and improving stent efficacy have been and are being investigated, including stent architecture and design, biomaterials, and coatings. This article provides an update on currently researched and available stents as well as future perspectives.

Problems and solutions of stent biofilm and encrustations: A review of literature

A ureteral stent is a commonly implanted urological device in patients with urinary tract obstruction. The main role of these stents is to allow adequate drainage of urine from the kidney into the bladder. Individuals with strictures, tumors, or obstructions from urinary stones do not have adequate urine flow and require ureteral stents as a part of their treatment to avoid potential hydronephrosis and renal failure. Although ureteral stents are highly effective in treating urinary tract obstructions, they have associated morbidities, such as biofilm formation and encrustation. Researchers have studied about how to diminish these negative outcomes by developing novel stent materials. Different coatings and biomaterials have been developed to reduce bacterial adhesion and crystal deposition onto the stent surfaces. Moreover, new investigation technologies, such as microfluidic platforms and encrustation sensors, have been utilized to better study the stents. Biofilms and encrustations can stem from bacterial origins; therefore, understanding the urinary microbiome will also provide insight into the solutions for treating them. There are still some gaps in our knowledge regarding the exact underlying mechanisms of stent-associated biofilms and encrustation. Future studies should include continuous testing of novel stent biomaterials for safety and efficacy, developing new technologies for identifying and extracting biofilms, enriching the assessment of stent encrustation, and diving deeper into understanding the urinary microbiome.

Strategies to Improve Patient Outcomes and QOL: Current Complications of the Design and Placements of Ureteric Stents

Ureteric stents have played a vital role in relieving urinary obstruction in many urological conditions. Although they are extremely successful, stents have been associated with complications and reduced patients' health-related quality of life (HRQoL). There are many factors that may affect the quality and longevity of stents. In this review, we have highlighted the journey and innovation of ureteric stents through the modern day. A literature review was conducted to identify relevant articles over the last 20 years. There is a plethora of evidence with various indications for the use of ureteral stents and how they affect QoL. There is still ongoing research to develop the ideal stent with reduced encrustation, one that resists infection and is also comfortable for the patients. Stents made from metal alloys, polymers and biodegradable materials have unique properties in their own right but also have certain deficiencies. These have been discussed along with an overview of newly developed stents. Certain pharmacological adjuncts have also been highlighted that may be useful to improve patient's tolerance to stents. In summary, this paper describes the features of the different types of stents and the problems that are frequently encountered, including effect on patients' HRQoL and financial burden to healthcare providers.

A case report of endorectal displacement of a right ureteral stent following radiochemotherapy and Bevacizumab

Background

The angiogenesis inhibitor monoclonal antibody Bevacizumab is presently the standard treatment for numerous neoplasms but particular toxicities are emerging, such as hypertension, haemorrhage, thromboembolism, gastrointestinal perforation, fistulae, and delayed wound healing. The addition of Bevacizumab to radio and chemotherapy has improved the overall survival rate in patients with metastatic, persistent or recurrent cervical carcinoma. However an increased risk of enteric or urinary fistula formation has been documented, related to hypoxia which is induced by the inhibition of angiogenesis. Moreover, previous pelvic surgery, repeated ureteral stenting and radiation are additional risk factors.

Case presentation

We describe the remarkable case of a right ureteral stent displacement inside the rectum lumen in a patient treated with Bevacizumab for pelvic recurrence of cervical cancer. The patient was referred to our Urology Department with urinary sepsis and bilateral hydronephrosis. Right ureteral stent substitution was planned; at cystoscopy the distal loop of the stent was not visualized inside the bladder. The presence of the distal loop of the right ureteral inside the rectum was clearly demonstrated with a CT scan.

Conclusions

Since Bevacizumab is increasingly used in the treatment of gynaecological neoplasms and indwelling ureteral stents are often required to treat or prevent ureteral compressions, similar cases are likely to be diagnosed and this complication should be considered in the management of advanced pelvic cancers.

Latest advancements in ureteral stent technology

Urological diseases such as tumours, kidney stones, or strictures in the ureter can lead to a number of health consequences, including life-threatening complications. Ureteral stents have been widely used as a valid solution to restore compromised urological function. Despite their clinical success, stents are subject to failure due to encrustation and biofilm formation, potentially leading to urinary tract infection. The current review focuses on recent advancements in ureteral stent technology, which have been reported in recent scientific journals or patents. Web of Science and Google Scholar have been used as a search engine to perform this review, using the keywords "Ureteral + Stent + Design", "Ureteral + Stent + Material + Coating", "Ureteric + Stent" and "Ureteral + Stent". A significant proportion of technological developments has focused on innovating the stent design to overcome migration and urinary reflux, as well as investigating novel materials and coatings to prevent biofilm formation, such as poly(N,N-dimethylacrylamide) (PDMMA) and swellable polyethylene glycol diacrylate (PEGDA). Biodegradable ureteral stents (BUS) have also emerged as a new generation of endourological devices, overcoming the "forgotten stent syndrome" and reducing healthcare costs. Moreover, efforts have been made to develop pre-clinical test methods, both experimental and computational, which could be employed as a screening platform to inform the design of novel stent technologies.