Modulation of crystalline Proteus mirabilis biofilm development on urinary catheters

Characterization, genome analysis and antibiofilm efficacy of lytic Proteus phages RP6 and RP7 isolated from university hospital sewage

The crystalline formation of biofilms by Proteus blocks the urine flow which often complicates the health care of catheterized patients. Bacteriophages has been highlighted as a promising tool to control biofilm-mediated bacterial infections. Here, we isolated and characterized two newly isolated lytic phages capable of infecting clinical isolates of P. mirabilis and P. vulgaris. Moreover, insights regarding the biological and molecular characterization were analysed. Both RP6 and RP7 phages showed a Proteus-genus-specific profile, administering no lytic activity against other family of Enterobacteriaceae. The optimal MOI value of the RP6 and RP7 phages were determined as 0.1 and 0.01, respectively. The one-step growth curve showed that RP6 and RP7 phages have a short latent period of 20 min and large burst size of 220-371 PFU/ML per infected host cell. Bacteria growth was reduced immediately after the phages were added, which is shown by the optical density (OD) measurement after 24 hr. Proteus phage RP6 and RP7 were found to eradicate both the planktonic and mature biofilms produced by the Proteus isolates tested. Genome sequence of Proteus phage RP6 was found to be 58,619 bp, and a G-C content of 47%. Also, Proteus phage RP7 genome size was 103,593 bp with G-C ratio of 38.45%. A total of 70 and 172 open reading frame (ORF) was encoded in RP6 and RP7 phage genomes, respectively. Interestingly, there were no tRNA encoded by Proteus phage RP6 genome even though there is a significant G-C content difference between the phage and its host. Additionally, the exhibition of highly lytic activity and absence of virulence and antibiotic-resistant genes in both Proteus RP6 and RP7 phages emphasized that this newly isolated phages are promising for potential therapeutic phages.

A Phage Cocktail To Control Surface Colonization by Proteus mirabilis in Catheter-Associated Urinary Tract Infections

Proteus mirabilis is a biofilm-forming bacterium and one of the most common causes of catheter-associated urinary tract infections (CAUTIs). The rapid spread of multidrug-resistant P. mirabilis represents a severe threat to management of nosocomial infections. This study aimed to isolate a potent phage cocktail and assess its potential to control urinary tract infections caused by biofilm-forming P. mirabilis. Two lytic phages, Isf-Pm1 and Isf-Pm2, were isolated and characterized by proteome analysis, transmission electron microscopy, and whole-genome sequencing. The host range and effect of the phage cocktail to reduce the biofilm formation were assessed by a cell adhesion assay in Vero cells and a phantom bladder model. The samples treated with the phage cocktail showed a significant reduction (65%) in the biofilm mass. Anti-quorum sensing and quantitative real-time PCR assays were also used to assess the amounts of transcription of genes involved in quorum sensing and biofilm formation. Furthermore, the phage-treated samples showed a downregulation of genes involved in the biofilm formation. In conclusion, these results highlight the efficacy of two isolated phages to control the biofilms produced by P. mirabilis CAUTIs. IMPORTANCE The rapid spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) bacterial strains and biofilm formation of bacteria have severely restricted the use of antibiotics and become a challenging issue in hospitals. Therefore, there is a necessity for alternative or complementary treatment measures, such as the use of virulent bacteriophages (phages), as effective therapeutic strategies.

Dynamically crosslinked polydimethylsiloxane-based polyurethanes with contact-killing antimicrobial properties as implantable alloplasts for urological reconstruction

A large population of patients is reported to suffer from urinary bladder-associated irreversible physiological disorders, rationalizing a continuous surge for structural and functional substitutes of urinary tissues, including ureters, bladder-wall, and urethra. The current gold standard for bladder reconstruction, an autologous gastrointestinal graft, is proven not to be an ideal substitute in the clinic. While addressing this unmet clinical need, a unique platform of antimicrobial polydimethyl siloxane-modified polyurethanes (TPU/PDMS) is designed and developed for its potential application as a urological implant. To the best of our knowledge, this study reports for the first time the successful integration of varying contents of PDMS within the molten polyurethane matrix using in situ crosslinking methodology. Thus, compatibilized binary blends possess clinically relevant viscoelastic properties to sustain high pressure, large distensions, and surgical manipulation. Furthermore, different chemical strategies are explored to covalently incorporate quaternized moieties, including 4-vinyl pyridine (4-VP), branched-polyethyleneimine (bPEI) as well as bPEI-grafted-(acrylic acid-co-vinylbenzyltriphenyl phosphonium chloride) (PAP), and counter urinary tract infections. The modified compositions, endowed with contact killing surfaces, reveal nearly three log reduction in bacterial growth in pathogenically infected artificial urine. Importantly, the antimicrobial TPU/PDMS blends support the uninhibited growth of mitochondrially viable murine fibroblasts, in a manner comparable to the medical-grade polyurethane. Collectively, the obtained results affirmed the newly developed polymers as promising biomaterials in reconstructive urology. STATEMENT OF SIGNIFICANCE: The clinical procedure for end-stage bladder disease remains replacement or augmentation of the bladder wall with a section of the patient's gastrointestinal tract. However, the absorptive and mucus-producing epithelium of intestinal segment is liable to short- and long-term complications. The dynamically crosslinked polydimethyl siloxane-based polyurethanes proposed herein, and the associated synthesis strategies to induce polycation grafted non-exhaustive contact-killing surfaces against uropathogents, have a significant clinical prospect in reconstructive urology. As an 'off-the-shelf' available alloplastic substitute, these blends offer the potential to circumvent the challenges associated with non-urinary autografts or scaffold based regenerative engineering and, thereby, shorten as well as simplify the surgical treatment. The targeted application has been conceived for a bladder patch to assist in various urinary diseases including, bladder carcinoma, refractory overactive bladder, interstitial cystitis, etc. However, given the ease of fabrication, moldability and the wide spectrum of mechanical properties that could be encompassed, these blends also present the possibility to be manifested into artificial ureteral or urethral conduits.

Infection-Triggered, Self-Cleaning Surfaces with On-Demand Cleavage of Surface-Localized Surfactant Moieties

Biofouling of surfaces is a major cause of infection and leads to significant patient morbidity and mortality within healthcare settings. With ever-increasing concerns over antibiotic resistance and associated challenges in eradicating surface-attached biofilm communities, efficacious antifouling materials are urgently required. We herein describe the development of an inherently antiadherent polymer system with the capacity for on-demand cleavage of surface-localized surfactant moieties. The nonionic surfactant, Triton X-100, was linked to hydrogel monomers via hydrolytically labile ester bonds. Synthesized copolymers exhibited pH-dependent switching of surfactant release, with elution triggered under the alkaline conditions characteristic of catheter-associated urinary tract infections and subsequently slowed down as the pH decreased, representing eradication of infection. In addition, the materials demonstrated complete resistance to adherence of Staphylococcus aureus following 24 h incubation in infected artificial urine, with reductions in adherence of Proteus mirabilis of up to 89% also observed. This dual-pronged approach with active, infection-responsive cleavage of surfactant to enhance the antiadherent properties of the surfactant-modified surfaces represents a promising self-cleaning strategy without associated concerns over bacterial resistance.

Multifunctional, Low Friction, Antimicrobial Approach for Biomaterial Surface Enhancement

Poly(vinyl chloride) (PVC) biomaterials perform a host of life-saving and life-enhancing roles when employed as medical devices within the body. High frictional forces between the device surface and interfacing tissue can, however, lead to a host of complications including tissue damage, inflammation, pain, and infection. We herein describe a versatile surface modification method using multifunctional hydrogel formulations to increase lubricity and prevent common device-related complications. In a clinically relevant model of the urinary tract, simulating the mechanical and biological environments encountered in vivo, coated candidate catheter surfaces demonstrated significantly lower frictional resistance than uncoated PVC, with reductions in coefficient of friction values of more than 300-fold due to hydration of the surface-localized polymer network. Furthermore, this significant lubrication capacity was retained following hydration periods of up to 28 days in artificial urine at pH 6 and pH 9, representing the pH of physiologically normal and infected urine, respectively, and during 200 repeated cycles of applied frictional force. Importantly, the modified surfaces also displayed excellent antibacterial activity, which could be facilely tuned to achieve reductions of 99.8% in adherence of common hospital-acquired pathogens, Staphylococcus aureus and Proteus mirabilis, relative to their uncoated counterparts through incorporation of chlorhexidine in the coating matrix as a model antiseptic. The remarkable, and pH-independent, tribological performance of these lubricious, antibacterial, and highly durable surfaces offers exciting promise for use of this PVC functionalization approach in facilitating smooth and atraumatic insertion and removal of a wide range of medical implants, ultimately maintaining user health and dignity.

Bacterial biofilm formation on indwelling urethral catheters

Urethral catheters are the most commonly deployed medical devices and used to manage a wide range of conditions in both hospital and community care settings. The use of long-term catheterization, where the catheter remains in place for a period >28 days remains common, and the care of these patients is often undermined by the acquisition of infections and formation of biofilms on catheter surfaces. Particular problems arise from colonization with urease-producing species such as Proteus mirabilis, which form unusual crystalline biofilms that encrust catheter surfaces and block urine flow. Encrustation and blockage often lead to a range of serious clinical complications and emergency hospital referrals in long-term catheterized patients. Here we review current understanding of bacterial biofilm formation on urethral catheters, with a focus on crystalline biofilm formation by P. mirabilis, as well as approaches that may be used to control biofilm formation on these devices. SIGNIFICANCE AND IMPACT OF THE STUDY: Urinary catheters are the most commonly used medical devices in many healthcare systems, but their use predisposes to infection and provide ideal conditions for bacterial biofilm formation. Patients managed by long-term urethral catheterization are particularly vulnerable to biofilm-related infections, with crystalline biofilm formation by urease producing species frequently leading to catheter blockage and other serious clinical complications. This review considers current knowledge regarding biofilm formation on urethral catheters, and possible strategies for their control.

Responsive and Synergistic Antibacterial Coatings: Fighting against Bacteria in a Smart and Effective Way

Antibacterial coatings that eliminate initial bacterial attachment and prevent subsequent biofilm formation are essential in a number of applications, especially implanted medical devices. Although various approaches, including bacteria-repelling and bacteria-killing mechanisms, have been developed, none of them have been entirely successful due to their inherent drawbacks. In recent years, antibacterial coatings that are responsive to the bacterial microenvironment, that possess two or more killing mechanisms, or that have triggered-cleaning capability have emerged as promising solutions for bacterial infection and contamination problems. This review focuses on recent progress on three types of such responsive and synergistic antibacterial coatings, including i) self-defensive antibacterial coatings, which can "turn on" biocidal activity in response to a bacteria-containing microenvironment; ii) synergistic antibacterial coatings, which possess two or more killing mechanisms that interact synergistically to reinforce each other; and iii) smart "kill-and-release" antibacterial coatings, which can switch functionality between bacteria killing and bacteria releasing under a proper stimulus. The design principles and potential applications of these coatings are discussed and a brief perspective on remaining challenges and future research directions is presented.

Encapsulation of Biological Agents in Hydrogels for Therapeutic Applications

Hydrogels are materials specially suited for encapsulation of biological elements. Their large water content provides an environment compatible with most biological molecules. Their crosslinked nature also provides an ideal material for the protection of encapsulated biological elements against degradation and/or immune recognition. This makes them attractive not only for controlled drug delivery of proteins, but they can also be used to encapsulate cells that can have therapeutic applications. Thus, hydrogels can be used to create systems that will deliver required therapies in a controlled manner by either encapsulation of proteins or even cells that produce molecules that will be released from these systems. Here, an overview of hydrogel encapsulation strategies of biological elements ranging from molecules to cells is discussed, with special emphasis on therapeutic applications.

Evaluation of a ureteral catheter coating by means of a BioEncrustation in vitro model

Biomaterials for applications in the urinary tract are challenged with both biofilm formation and encrustation, two highly interconnected processes. While great effort has been achieved developing promising materials there is only a limited choice of sophisticated in vitro models that are available to analyse the performance of biomaterials prior to performing delicate and expensive in vivo studies. In this study we present a complex BioEncrustation model that imitates both the processes of multi-species biofilm formation and encrustation in vitro. The resulting crystalline biofilms are compared to the deposits found on explanted ureteral stent surfaces (in vivo situation) and to deposits formed in an experimental set up that does not contain bacteria (Encrustator®). Further focus of this study is dedicated to employing the developed BioEncrustation model to evaluate the effect multifunctional coatings impose on the processes of biofilm formation and encrustation under in vitro conditions. The investigated TANP coating combines unspecific and broad band specific antibacterial properties with a degrading polymer matrix that is intended to inhibit crystal formation. The coating was prepared on both polyurethane and silicone tubes and the subsequent results of the in vitro BioEncrustation analyses reveal a promising potential for employing the coating to render ureteral stent surfaces more biocompatible.

Role of nutrient limitation in the competition between uropathogenic strains of Klebsiella pneumoniae and Escherichia coli in mixed biofilms

Klebsiella pneumoniae and Escherichia coli form mixed species biofilms in catheter-associated urinary tract infections. Recently, a detrimental effect of K. pneumoniae over E. coli was observed in mixed species biofilms grown in an artificial urine medium. The mechanism behind this competitive interaction was studied. K. pneumoniae partially outcompeted E. coli in early-stage batch-fed biofilms, whereas both microorganisms co-exist at longer times (K. pneumoniae:E. coli ratio, 55:1), as shown by cell counts and confocal microscopy. E. coli cells were scattered along the K. pneumoniae biofilm. Biofilm supernatants did not appear to contain either antimicrobial or anti-biofilm activities against E. coli. Biofilms grown under continuous flow prevented interspecies competition. K. pneumoniae showed both increased siderophore production and better growth in iron-limited media compared to E. coli. In summary, these results indicate the importance of nutrient (particularly iron) competition in the modulation of the bacterial composition of mixed species biofilms formed by uropathogenic K. pneumoniae and E. coli.

Anti-Adherent Biomaterials for Prevention of Catheter Biofouling

Medical device-associated infections present a leading global healthcare challenge, and effective strategies to prevent infections are urgently required. Herein, we present an innovative anti-adherent hydrogel copolymer as a candidate catheter coating with complementary hydrophobic drug-carrying and eluting capacities. The amphiphilic block copolymer, Poloxamer 188, was chemically-derivatized with methacryloyl moieties and copolymerized with the hydrogel monomer, 2-hydroxyethyl methacrylate. Performance of the synthesized copolymers was evaluated in terms of equilibrium swelling, surface water wettability, mechanical integrity, resistance to encrustation and bacterial adherence, and ability to control release of the loaded fluoroquinolone antibiotic, ofloxacin. The developed matrices were able to provide significant protection from fouling, with observed reductions of over 90% in both adherence of the common urinary pathogen Escherichia coli and encrusting crystalline deposits of calcium and magnesium salts relative to the commonly employed hydrogel, poly (hydroxyethyl methacrylate). Additionally, the release kinetics of a loaded hydrophobic drug could be readily tuned through facile manipulation of polymer composition. This combinatorial approach shows significant promise in the development of suitable systems for prevention of catheter-associated infections.

Study of Crystal Formation and Nitric Oxide (NO) Release Mechanism from S-Nitroso-N-acetylpenicillamine (SNAP)-Doped CarboSil Polymer Composites for Potential Antimicrobial Applications

Stable and long-term nitric oxide (NO) releasing polymeric materials have many potential biomedical applications. Herein, we report the real-time observation of the crystallization process of the NO donor, S-nitroso-N-acetylpenicillamine (SNAP), within a thermoplastic silicone-polycarbonate-urethane biomedical polymer, CarboSil 20 80A. It is demonstrated that the NO release rate from this composite material is directly correlated with the surface area that the CarboSil polymer film is exposed to when in contact with aqueous solution. The decomposition of SNAP in solution (e.g. PBS, ethanol, THF, etc.) is a pseudo-first-order reaction proportional to the SNAP concentration. Further, catheters fabricated with this novel NO releasing composite material are shown to exhibit significant effects on preventing biofilm formation on catheter surface by Pseudomonas aeruginosa and Proteus mirabilis grown in CDC bioreactor over 14 days, with a 2 and 3 log-unit reduction in number of live bacteria on their surfaces, respectively. Therefore, the SNAP-CarboSil composite is a promising new material to develop antimicrobial catheters, as well as other biomedical devices.

Prevention of encrustation and blockage of urinary catheters by Proteus mirabilis via pH-triggered release of bacteriophage

The crystalline biofilms of Proteus mirabilis can seriously complicate the care of patients undergoing long-term indwelling urinary catheterisation. Expression of bacterial urease causes a significant increase in urinary pH, leading to the supersaturation and precipitation of struvite and apatite crystals. These crystals become lodged within the biofilm, resulting in the blockage of urine flow through the catheter. Here, we describe an infection-responsive surface coating for urinary catheters, which releases a therapeutic dose of bacteriophage in response to elevated urinary pH, in order to delay catheter blockage. The coating employs a dual-layered system comprising of a lower hydrogel 'reservoir' layer impregnated with bacteriophage, capped by a 'trigger' layer of the pH-responsive polymer poly(methyl methacrylate-co-methacrylic acid) (EUDRAGIT®S 100). Evaluation of prototype coatings using a clinically reflective in vitro bladder model system showed that catheter blockage time was doubled (13 h to 26 h (P < 0.05)) under conditions of established infection (10⁸ CFU ml^-1) in response to a 'burst-release' of bacteriophage (10⁸ PFU ml^-1). Coatings were stable both in the absence of infection, and in the presence of urease-negative bacteria. Quantitative and visual analysis of crystalline biofilm reduction show that bacteriophage constitute a promising strategy for the prevention of catheter blockage, a clinical problem for which there is currently no effective control method.

Conjugation of Lectin to Poly(ε-caprolactone)-block-glycopolymer Micelles for In Vitro Intravesical Drug Delivery

Amphiphilic poly(ε-caprolactone)-block-poly[2-(α-d-mannopyranosyloxy) ethyl acrylamide] (PCL-b-PManEA) block copolymers were synthesized via a combination of ring-opening polymerization (ROP), reversible addition-fragmentation chain transfer (RAFT) polymerization and reactive ester-amine reaction. The PCL-b-PManEA block copolymers can self-assemble into micelles and encapsulate anticancer drug doxorubicin (DOX). To enhance mucoadhesive property of the resulting DOX-loaded PCL-b-PManEA micelles, Concanavalin A (ConA) lectin was further conjugated with the micelles. Turbidimetric assay using mucin shows that the DOX-loaded PCL-b-PManEA@ConA micelles are mucoadhesive. DOX release from the DOX-loaded PCL-b-PManEA@ConA micelles in artificial urine at 37 °C exhibits an initial burst release, followed by a sustained and slow release over three days. Confocal laser scanning microscope (CLSM) images indicate that the DOX-loaded PCL-b-PManEA@ConA micelles can be effectively internalized by UMUC3 human urothelial carcinoma cells. The DOX-loaded PCL-b-PManEA@ConA micelles exhibit significant cytotoxicity to these cells.

Testing a Model of Self-Management of Fluid Intake in Community-Residing Long-term Indwelling Urinary Catheter Users

BACKGROUND

Urinary tract infection and blockage are serious and recurrent challenges for people with long-term indwelling catheters, and these catheter problems cause worry and anxiety when they disrupt normal daily activities.

OBJECTIVE

The goal was to determine whether urinary catheter-related self-management behaviors focusing on fluid intake would mediate fluid intake-related self-efficacy toward decreasing catheter-associated urinary tract infection (CAUTI) and/or catheter blockage.

METHODS

The sample involved data collected from 180 adult community-living, long-term indwelling urinary catheter users. The authors tested a model of fluid intake self-management related to fluid intake self-efficacy for key outcomes of CAUTI and blockage. To account for the large number of zeros in both outcomes, a zero-inflated negative binomial (ZINB) structural equation model was tested.

RESULTS

Structurally, fluid intake self-efficacy was positively associated with fluid intake self-management, suggesting that higher fluid intake self-efficacy predicts more (higher) fluid intake self-management; however, fluid intake self-management was not associated with either the frequency of CAUTIs or the presence or absence of CAUTI. Fluid intake self-efficacy was positively related to fluid intake self-management, and fluid intake self-management predicted less frequency of catheter blockage, but neither fluid intake self-efficacy nor fluid intake self-management predicted the presence or absence of blockage.

DISCUSSION

Further research is needed to better understand determinants of CAUTI in long-term catheter users and factors which might influence or prevent its occurrence. Increased confidence (self-efficacy) and self-management behaviors to promote fluid intake could be of value to long-term urinary catheter users to decrease catheter blockage.

An Infection-Responsive Approach To Reduce Bacterial Adhesion in Urinary Biomaterials

Infection is an inevitable consequence of chronic urinary catheterization with associated problems of recurrent catheter encrustation and blockage experienced by approximately 50% of all long-term catheterized patients. In this work, we have exploited, for the first time, the reported pathogen-induced elevation of urine pH as a trigger for "intelligent" antimicrobial release from novel hydrogel drug delivery systems of 2-hydroxyethyl methacrylate and vinyl-functionalized nalidixic acid derivatives, developed as candidate infection-resistant urinary catheter coatings. Demonstrating up to 20-fold faster rates of drug release at pH 10, representing infected urine pH, than at pH 7 and achieving reductions of up to 96.5% in in vitro bacterial adherence, our paradigm of pH-responsive drug delivery, which requires no external manipulation, therefore represents a promising development toward the prevention of catheter-associated urinary tract infections in vivo.

Development of a Phage Cocktail to Control Proteus mirabilis Catheter-associated Urinary Tract Infections

Proteus mirabilis is an enterobacterium that causes catheter-associated urinary tract infections (CAUTIs) due to its ability to colonize and form crystalline biofilms on the catheters surface. CAUTIs are very difficult to treat, since biofilm structures are highly tolerant to antibiotics. Phages have been used widely to control a diversity of bacterial species, however, a limited number of phages for P. mirabilis have been isolated and studied. Here we report the isolation of two novel virulent phages, the podovirus vB_PmiP_5460 and the myovirus vB_PmiM_5461, which are able to target, respectively, 16 of the 26 and all the Proteus strains tested in this study. Both phages have been characterized thoroughly and sequencing data revealed no traces of genes associated with lysogeny. To further evaluate the phages’ ability to prevent catheter’s colonization by Proteus, the phages adherence to silicone surfaces was assessed. Further tests in phage-coated catheters using a dynamic biofilm model simulating CAUTIs, have shown a significant reduction of P. mirabilis biofilm formation up to 168 h of catheterization. These results highlight the potential usefulness of the two isolated phages for the prevention of surface colonization by this bacterium.

Molecular identification of multi drug resistant bacteria from urinary tract infected urine samples

Urinary tract infections (UTIs) are of great concern in both developing and developed countries all over the world. Even though the infections are more common in women and children, they are at a considerable rate in men and of all ages. The uropathogens causing the infections are spread through various routes. The treatment generally recommended by the physicians is antibiotic usage. But, most of the uropathogens have evolved antibiotic resistance mechanisms. This makes the present situation hectic in control and prevention of UTIs. The present study aims to illustrate the multidrug resistance patterns among isolated bacterial strains from infected urine samples in Odisha state, India. Four bacterial strains were isolated and identified as Proteus sp. SK3, Pseudomonas sp. ADMK77, Proteus sp. BLKB2 and Enterobacter hormaechei strain CW-3 by 16S rRNA gene sequencing. Phylogenetc analysis indicated the strains belong to three various genera namely, Proteus, Pseudomonas and Enterobacter. The evolutionary timeline of the bacteria was studied by constructing phylogenetic trees by Neighborhood Joining method. The presence of ESBL gene and biofilm forming capability were studied for the four strains. Antibiotic susceptibility patterns of the isolates were studied toward the commonly recommended antibiotics. Both the Proteus strains were found commonly susceptible to aminoglycoside and sulphonamide groups. Pseudomonas strain was found to be susceptible to cephems, aminoglycosides and fluoroquinolones. Enterobacter sp was found to be resistant to almost all antibiotic groups and susceptible to only sulphonamides group. The antibiotic susceptibility patterns of the bacteria help in choosing the empirical antibiotic treatment for UTI.

Novel Insights into the Proteus mirabilis Crystalline Biofilm Using Real-Time Imaging

The long-term use of indwelling catheters results in a high risk from urinary tract infections (UTI) and blockage. Blockages often occur from crystalline deposits, formed as the pH rises due to the action of urease-producing bacteria; the most commonly found species being Proteus mirabilis. These crystalline biofilms have been found to develop on all catheter materials with P. mirabilis attaching to all surfaces and forming encrustations. Previous studies have mainly relied on electron microscopy to describe this process but there remains a lack of understanding into the stages of biofilm formation. Using an advanced light microscopy technique, episcopic differential interference contrast (EDIC) microscopy combined with epifluorescence (EF), we describe a non-destructive, non-contact, real-time imaging method used to track all stages of biofilm development from initial single cell attachment to complex crystalline biofilm formation. Using a simple six-well plate system, attachment of P. mirabilis (in artificial urine) to sections of silicone and hydrogel latex catheters was tracked over time (up to 24 days). Using EDIC and EF we show how initial attachment occurred in less than 1 h following exposure to P. mirabilis. This was rapidly followed by an accumulation of an additional material (indicated to be carbohydrate based using lectin staining) and the presence of highly elongated, motile cells. After 24 h exposure, a layer developed above this conditioning film and within 4 days the entire surface (of both catheter materials) was covered with diffuse crystalline deposits with defined crystals embedded. Using three-dimensional image reconstruction software, cells of P. mirabilis were seen covering the crystal surfaces. EDIC microscopy could resolve these four components of the complex crystalline biofilm and the close relationship between P. mirabilis and the crystals. This real-time imaging technique permits study of this complex biofilm development with no risk of artefacts due to sample manipulation. A full understanding of the stages and components involved in crystalline encrustation formation will aid in the development of new protocols to manage and ultimately prevent catheter blockage.

Urinary catheters: history, current status, adverse events and research agenda

For more than 3500 years, urinary catheters have been used to drain the bladder when it fails to empty. For people with impaired bladder function and for whom the method is feasible, clean intermittent self-catheterization is the optimal procedure. For those who require an indwelling catheter, whether short- or long-term, the self-retaining Foley catheter is invariably used, as it has been since its introduction nearly 80 years ago, despite the fact that this catheter can cause bacterial colonization, recurrent and chronic infections, bladder stones and septicaemia, damage to the kidneys, the bladder and the urethra, and contribute to the development of antibiotic resistance. In terms of medical, social and economic resources, the burden of urinary retention and incontinence, aggravated by the use of the Foley catheter, is huge. In the UK, the harm resulting from the use of the Foley catheter costs the National Health Service between £1.0-2.5 billion and accounts for ∼2100 deaths per year. Therefore, there is an urgent need for the development of an alternative indwelling catheter system. The research agenda is for the new catheter to be easy and safe to insert, either urethrally or suprapubically, to be retained reliably in the bladder and to be withdrawn easily and safely when necessary, to mimic natural physiology by filling at low pressure and emptying completely without damage to the bladder, and to have control mechanisms appropriate for all users.

S-Nitroso-N-acetylpenicillamine (SNAP) Impregnated Silicone Foley Catheters: A Potential Biomaterial/Device To Prevent Catheter-Associated Urinary Tract Infections

Urinary Foley catheters are utilized for management of hospitalized patients and are associated with high rates of urinary tract infections (UTIs). Nitric oxide (NO) potently inhibits microbial biofilm formation, which is the primary cause of catheter associated UTIs (CAUTIs). Herein, commercial silicone Foley catheters are impregnated via a solvent swelling method with S-nitroso-N-acetyl-D-penicillamine (SNAP), a synthetic NO donor that exhibits long-term NO release and stability when incorporated into low water-uptake polymers. The proposed catheters generate NO surface-fluxes >0.7 × 10^–10 mol min^–1 cm^–2 for over one month under physiological conditions, with minimal SNAP leaching. These biomedical devices are demonstrated to significantly decrease formation of biofilm on the surface of the catheter tubings over 3, 7, and 14 day periods by microbial species (Staphylococcus epidermidis and Proteus mirabilis) commonly causing CAUTIs. Toxicity assessment demonstrates that the SNAP-impregnated catheters are fully biocompatible, as extracts of the catheter tubings score 0 on a 3-point grading scale using an accepted mouse fibroblast cell-line toxicity model. Consequently, SNAP-impregnated silicone Foley catheters can likely provide an efficient strategy to greatly reduce the occurrence of nosocomial CAUTIs.

Ultrashort cationic naphthalene-derived self-assembled peptides as antimicrobial nanomaterials

Self-assembling dipeptides conjugated to naphthalene show considerable promise as nanomaterial structures, biomaterials, and drug delivery devices. Biomaterial infections are responsible for high rates of patient mortality and morbidity. The presence of biofilm bacteria, which thrive on implant surfaces, are a huge burden on healthcare budgets, as they are highly resistant to current therapeutic strategies. Ultrashort cationic self-assembled peptides represent a highly innovative and cost-effective strategy to form antibacterial nanomaterials. Lysine conjugated variants display the greatest potency with 2% w/v NapFFKK hydrogels significantly reducing the viable Staphylococcus epidermidis biofilm by 94%. Reducing the size of the R-group methylene chain on cationic moieties resulted in reduction of antibiofilm activity. The primary amine of the protruding R-group tail may not be as readily available to interact with negatively charged bacterial membranes. Cryo-SEM, FTIR, CD spectroscopy, and oscillatory rheology provided evidence of supramolecular hydrogel formation at physiological pH (pH 7.4). Cytotoxicity assays against murine fibroblast (NCTC 929) cell lines confirmed the gels possessed reduced cytotoxicity relative to bacterial cells, with limited hemolysis upon exposure to equine erythrocytes. The results presented in this paper highlight the significant potential of ultrashort cationic naphthalene peptides as future biomaterials.

Clinical complications of urinary catheters caused by crystalline biofilms: something needs to be done

This review is largely based on a previous paper published in the journal Spinal Cord. The care of many patients undergoing long-term bladder catheterization is complicated by encrustation and blockage of their Foley catheters. This problem stems from infection by urease-producing bacteria, particularly Proteus mirabilis. These organisms colonize the catheter forming an extensive biofilm; they also generate ammonia from urea, thus elevating the pH of urine. As the pH rises, crystals of calcium and magnesium phosphates precipitate in the urine and in the catheter biofilm. The continued development of this crystalline biofilm blocks the flow of urine through the catheter. Urine then either leaks along the outside of the catheter and the patient becomes incontinent or is retained causing painful distension of the bladder and reflux of urine to the kidneys. The process of crystal deposition can also initiate stone formation. Most patients suffering from recurrent catheter encrustation develop bladder stones. P. mirabilis establishes stable residence in these stones and is extremely difficult to eliminate from the catheterized urinary tract by antibiotic therapy. If blocked catheters are not identified and changed, serious symptomatic episodes of pyelonephritis, septicaemia and endotoxic shock can result. All types of Foley catheters including silver- or nitrofurazone-coated devices are vulnerable to this problem. In this review, the ways in which biofilm formation on Foley catheters is initiated by P. mirabilis will be described. The implications of understanding these mechanisms for the development of an encrustation-resistant catheter will be discussed. Finally, the way forward for the prevention and control of this problem will be considered.

Evaluation of environmental scanning electron microscopy for analysis of Proteus mirabilis crystalline biofilms in situ on urinary catheters

Proteus mirabilis is a common cause of catheter-associated urinary tract infections and frequently leads to blockage of catheters due to crystalline biofilm formation. Scanning electron microscopy (SEM) has proven to be a valuable tool in the study of these unusual biofilms, but entails laborious sample preparation that can introduce artefacts, undermining the investigation of biofilm development. In contrast, environmental scanning electron microscopy (ESEM) permits imaging of unprocessed, fully hydrated samples, which may provide much insight into the development of P. mirabilis biofilms. Here, we evaluate the utility of ESEM for the study of P. mirabilis crystalline biofilms in situ, on urinary catheters. In doing so, we compare this to commonly used conventional SEM approaches for sample preparation and imaging. Overall, ESEM provided excellent resolution of biofilms formed on urinary catheters and revealed structures not observed in standard SEM imaging or previously described in other studies of these biofilms. In addition, we show that energy-dispersive X-ray spectroscopy (EDS) may be employed in conjunction with ESEM to provide information regarding the elemental composition of crystalline structures and demonstrate the potential for ESEM in combination with EDS to constitute a useful tool in exploring the mechanisms underpinning crystalline biofilm formation.

Biocide activity against urinary catheter pathogens

Antimicrobial effects of essential oils against bacteria associated with urinary catheter infection was assessed. Tests were performed on 14 different bacterial species cultured either planktonically or as biofilms. Biofilms were found to be up to 8-fold more tolerant of the test agents. Higher antimicrobial tolerance was also evident in tests conducted in artificial urine. Eugenol exhibited higher antimicrobial effects against both planktonic cells and biofilms than did terpinen, tea tree oil, and cineole.

Antibiotic resistance pattern among biofilm producing and non producing Proteus strains isolated from hospitalized patients; matter of hospital hygiene and antimicrobial stewardship

A retrospective study on antimicrobial susceptibility and biofilm production were carried out for eighty eight strains of Proteus strains isolated from UTI and other hospital samples during April 2011-April 2012. The antibiotic susceptibility was carried out by Kirby-Bauer disk diffusion and MIC by E-test. Biofilm production was measured by microtiter method and confirmed by Scanning electron microscopy. Plasmids from biofilm producing isolates were detected by alkaline lysis technique. From 88 patients infected by proteus species, 58% were female and 42% were mail. The most frequent age range was 20-29 (77.39%) and the least were 60-69 years old (3.4%) (p = 0.05). Eighty one isolates were identified as P. mirabilis while, 7 identified as P. vulgaris. 67.04% [n = 59] of the isolates showed MIC range (16-32 +/- 0.05 microg mL(-1)) to ceftriaxone, 46.59% [n = 41] exhibited least MIC range to chloramphenicol (8-64 +/- 0.08 microg mL(-1)). 31% [n = 28] of the isolates also exhibited MIC range 1-4 microg mL(-1) to ciprofloxacin. 17% [n = 15] of the isolates exhibited strong biofilm while, 6% [n = 6] did not show any biofilm (p < or = 0.05). Plasmid isolation from biofilm producing isolates revealed that stains number 19, 24 and 87' that produced strong biofilm carried similar high M. Wt. plasmid. From above results it can be concluded that the majority of Proteus isolated from UTI patients were belong to P. mirabilis. Ciprofloxacin was the most effective antibiotic for treatment of the infected patients. Limited number of the isolates could produce strong biofilm that were bearing plasmids. Majority of the biofilm producing isolates were also resistance at least to 4 antibiotics routinely prescribed in our hospital.

Polymeric nanoparticles with encapsulated superparamagnetic iron oxide and conjugated cisplatin for potential bladder cancer therapy

Amphiphilic poly(ε-caprolactone)-b-poly(propargyl methacrylate-click-mercaptosuccinic acid-co-poly(ethylene glycol) methyl ether methacrylate) (PCL-b-P(PMA-click-MSA-co-PEGMA)) were synthesized by a combination of ring-opening polymerization, reversible addition-fragmentation chain transfer (RAFT) polymerization, and thiol-yne "click" reaction. The hydrophobic PCL core can be used to load superparamagnetic iron oxide nanoparticles (SPIONs), while the pendant dicarboxylic groups in the hydrophilic shell are used to coordinate cisplatin. These SPIONs-loaded, cisplatin-conjugated polymeric nanoparticles (Pt-Fe-PNs) are superparamagnetic at room temperature and are mucoadhesive. Release of cisplatin from Pt-Fe-PNs in artificial urine at 37 °C was characterized by an initial burst release with a release of ∼30% of the cisplatin in the first 4 h followed by a slow sustained release over 4 days. The cisplatin release can be further enhanced by increasing the temperature. These Pt-Fe-PNs can effectively induce cytotoxicity against UMUC3 bladder cancer cells with IC(50) of 32.3 μM. These results indicate that Pt-Fe-PNs is potentially a promising cisplatin delivery vehicle which can be combined with SPIONs-induced hyperthermia for bladder cancer therapy.

The encrustation and blockage of long-term indwelling bladder catheters: a way forward in prevention and control

OBJECTIVES

To review the literature showing that understanding how Foley catheters become encrusted and blocked by crystalline bacterial biofilms has led to strategies for the control of this complication in the care of patients undergoing long-term indwelling bladder catheterization.

METHODS

A comprehensive PubMed search of the literature published between 1980 and December 2009 was made for relevant articles using the Medical Subject Heading terms 'biofilms', 'urinary catheterization', 'catheter-associated urinary tract infection' and 'urolithiasis'. Papers on catheter-associated urinary tract infections and bacterial biofilms collected during 40 years of working in the field were also reviewed.

RESULTS

There is strong experimental and epidemiological evidence that infection by Proteus mirabilis is the main cause of the crystalline biofilms that encrust and block Foley catheters. The ability of P. mirabilis to generate alkaline urine and to colonize all available types of indwelling catheters allows it to take up stable residence in the catheterized tract in bladder stones and cause recurrent catheter blockage.

CONCLUSION

The elimination of P. mirabilis by antibiotic therapy as soon as it appears in the catheterized urinary tract could improve the quality of life for many patients and reduce the current expenditure of resources when managing the complications of catheter encrustation and blockage. For patients who are already chronic blockers and stone formers, antibiotic treatment is unlikely to be effective owing to the resistance of cells in the crystalline biofilms. Strategies such as increasing fluid intake with citrated drinks could control the problem until bladder stone removal can be organized.

Strategy to control catheter encrustation with citrated drinks: a randomized crossover study

PURPOSE

Nucleation pH is the pH at which Ca and Mg come out of urine to form crystals. If the safety margin between voiding pH and nucleation pH could be increased, it would increase the possibility of an alternative to controlling the activity of urease producing bacteria as a strategy to control catheter encrustation.

MATERIALS AND METHODS

We performed a 6-week randomized crossover study in 24 patients with catheter blockage who were randomly allocated to a specific sequence of 3 consecutive available treatments, including increased fluid intake, lemon juice and potassium citrate. Each patient received all available regimens. At the end of each week 24-hour urine samples were analyzed for voiding and nucleation pH, citrate, Ca and Mg.

RESULTS

Mean +/- SD nucleation pH increased from 7.45 +/- 0.60 at baseline to 7.93 +/- 0.50, 7.68 +/- 0.64 and 7.96 +/- 0.37 in the lemon juice, increased fluid intake and potassium citrate groups, respectively (p <0.0001). Mean urinary citrate increased significantly (p <0.0001), in particular due to lemon juice and potassium citrate effects. The association between treatment and Ca was weak (p = 0.12) while that of Mg was negative due to lemon (p <0.001). Average increase in the safety margin (nucleation pH minus voiding pH) beyond baseline was 0.84 (95% CI 0.63-1.04), 0.57 (95% CI 0.37-0.78) and 0.41 (95% CI 0.20-0.61) for lemon juice, increased fluid intake and potassium citrate, respectively. A strong treatment effect on the safety margin was apparent even when controlling for study design (p <0.001).

CONCLUSIONS

Increased fluid intake with lemon juice may be a simple, inexpensive, effective strategy to control catheter encrustation.

Crystalline bacterial biofilm formation on urinary catheters by urease-producing urinary tract pathogens: a simple method of control

The problem of catheter encrustation stems from infection by urease-producing bacteria. These organisms generate ammonia from urea, elevate the pH of urine and cause crystals of calcium and magnesium phosphates to form in the urine and the biofilm that develops on the catheter. In this study, a laboratory model was used to compare the ability of 12 urease-positive species of urinary tract pathogens to encrust and block catheters. Proteus mirabilis, Proteus vulgaris and Providencia rettgeri were able to raise the urinary pH above 8.3 and produce catheter-blocking crystalline biofilms within 40 h. Morganella morganii and Staphylococcus aureus elevated the pH of urine to 7.4 and 6.9, respectively, and caused some crystal deposition in the biofilms but did not block catheters in the 96 h experimental period. Isolates of Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Serratia marcescens, Pseudomonas aeruginosa and Providencia stuartii were only capable of raising the pH of urine to a maximum of 6.4 and failed to cause crystal deposition in the biofilm. The most effective way to prevent catheter encrustation was shown to be diluting urine and increasing its citrate concentration. This strategy raises the nucleation pH (pH(n)) at which calcium and magnesium phosphates crystallize from urine. Increasing the fluid intake of a healthy volunteer with citrated drinks resulted in urine with a pH(n) of >8.0 in which catheter encrustation was inhibited. It is suggested that this dietary strategy will be an effective means of controlling catheter encrustation, whichever bacterial species is causing the problem.

The effect of EDTA instillations on the rate of development of encrustation and biofilms in Foley catheters

The aim of this research was to examine whether a daily instillation of tetra sodium ethylenediaminetetraacetic acid (EDTA) solution could reduce the rate at which encrustation by crystalline Proteus mirabilis biofilms blocks urinary catheters. Sets of three bladder models were fitted with size 14 all-silicone catheters. Tetra sodium EDTA solution was instilled into the catheter following biofilm development. Catheters were examined by digital photography and scanning electron microscopy for evidence of encrustation. The results showed that the mean time to blockage of the control catheters was 45 h for saline, 57 h for water and 67 h for those exposed to daily instillations of the EDTA solution. Statistical analysis confirmed that the mean encrustation rate on the EDTA-treated catheters was significantly lower than on the control-treated devices (P = 0.047). This in vitro study indicates that EDTA may have beneficial effects in reducing the complication of catheter encrustation and blockage by crystalline biofilms.

Biofilm and other causes of pain in catheterization

This article looks at the anatomy of the bladder and how sensations, including pain, are transmitted to the brain. The use of urinary catheters is discussed and initially, the development of biofilm is addressed, from its cause, structure and effect, to how it can be treated. Many of the problems arising from biofilm and the resulting encrustation, can lead to pain, and the causes of this are discussed. Other problems which can cause patients to experience pain are also considered, and where there are possible solutions, these have been put forward. However, even when good practice is carried out, there will still be problems encountered, and further research is needed.

Bacterial biofilms in patients with indwelling urinary catheters

Bacteria have a basic survival strategy: to colonize surfaces and grow as biofilm communities embedded in a gel-like polysaccharide matrix. The catheterized urinary tract provides ideal conditions for the development of enormous biofilm populations. Many bacterial species colonize indwelling catheters as biofilms, inducing complications in patients' care. The most troublesome complications are the crystalline biofilms that can occlude the catheter lumen and trigger episodes of pyelonephritis and septicemia. The crystalline biofilms result from infection by urease-producing bacteria, particularly Proteus mirabilis. Urease raises the urinary pH and drives the formation of calcium phosphate and magnesium phosphate crystals in the biofilm. All types of catheter are vulnerable to encrustation by these biofilms, and clinical prevention strategies are clearly needed, as bacteria growing in the biofilm mode are resistant to antibiotics. Evidence indicates that treatment of symptomatic, catheter-associated urinary tract infection is more effective if biofilm-laden catheters are changed before antibiotic treatment is initiated. Infection with P. mirabilis exposes the many faults of currently available catheters, and plenty of scope exists for improvement in both their design and production; manufacturers should take up the challenge to improve patient outcomes.

Observations on the development of the crystalline bacterial biofilms that encrust and block Foley catheters

The care of many patients undergoing long-term bladder catheterisation is complicated when the flow of urine through the catheter is blocked by encrustation. The problem results from infection by urease-producing bacteria, especially Proteus mirabilis, and the subsequent formation of crystalline biofilms on the catheter. The aim of this study was to discover how P. mirabilis initiates the development of these crystalline biofilms. The early stages in the formation of the biofilms were observed on a range of Foley catheters in a laboratory model of the catheterised bladder. Scanning electron micrographs revealed that when all-silicone, silicone-coated latex, hydrogel-coated latex, hydrogel/silver-coated latex and nitrofurazone silicone catheters were inserted into bladder models containing P. mirabilis and alkaline urine, their surfaces were rapidly coated with a microcrystalline foundation layer. X-ray microanalysis showed that this material was composed of calcium phosphate. Bacterial colonisation of the foundation layer followed and by 18h the catheters were encrusted by densely populated crystalline P. mirabilis biofilms. These observations have important implications for the development of encrustation-resistant catheters. In the case of silver catheters for example, bacterial cells can attach to the crystalline foundation layer and continue to grow, protected from contact with the underlying silver. If antimicrobials are to be incorporated into catheters to prevent encrustation, it is important that they diffuse into the urine and prevent the rise in pH that triggers crystal formation.

Complicated catheter-associated urinary tract infections due to Escherichia coli and Proteus mirabilis

Catheter-associated urinary tract infections (CAUTIs) represent the most common type of nosocomial infection and are a major health concern due to the complications and frequent recurrence. These infections are often caused by Escherichia coli and Proteus mirabilis. Gram-negative bacterial species that cause CAUTIs express a number of virulence factors associated with adhesion, motility, biofilm formation, immunoavoidance, and nutrient acquisition as well as factors that cause damage to the host. These infections can be reduced by limiting catheter usage and ensuring that health care professionals correctly use closed-system Foley catheters. A number of novel approaches such as condom and suprapubic catheters, intermittent catheterization, new surfaces, catheters with antimicrobial agents, and probiotics have thus far met with limited success. While the diagnosis of symptomatic versus asymptomatic CAUTIs may be a contentious issue, it is generally agreed that once a catheterized patient is believed to have a symptomatic urinary tract infection, the catheter is removed if possible due to the high rate of relapse. Research focusing on the pathogenesis of CAUTIs will lead to a better understanding of the disease process and will subsequently lead to the development of new diagnosis, prevention, and treatment options.

Candidate targets for new antivirulence drugs: selected cases of bacterial adhesion and biofilm formation

Management of bacterial infections is becoming increasingly difficult due to the rising frequency of strains that are resistant to many current antibiotics. New types of antibiotics are, therefore, urgently needed. Virulence factors or virulence-associated phenotypes such as adhesins and biofilm formation are highly attractive targets for new drugs. Specific adhesion provides bacteria with target selection and prevents removal by hydrodynamic flow forces. Bacterial adhesion is of paramount importance for bacterial pathogenesis. Adhesion is also the first step in biofilm formation. Biofilm formation is particularly problematic in medical contexts because biofilm-associated bacteria are particularly hard to eradicate. Several promising candidate drugs that target bacterial adhesion and biofilm formation are being developed. Some of these might be valuable weapons for fighting infectious diseases in the future. Here we use illustrative examples, mainly from the enterics, to demonstrate the principles.