Catheter-associated Urinary Tract Infection Model Research Articles

Function and contribution of two putative Enterococcus faecalis glycosaminoglycan degrading enzymes to bacteremia and catheter-associated urinary tract infection.

Enterococcus faecalis is a common cause of healthcare-acquired bloodstream infections and catheter-associated urinary tract infections (CAUTIs) in both adults and children. Treatment of E. faecalis infection is frequently complicated by multi-drug resistance. Based on protein homology, E. faecalis encodes two putative hyaluronidases, EF3023 (HylA) and EF0818 (HylB). In other Gram-positive pathogens, hyaluronidases have been shown to contribute to tissue damage and immune evasion, but the function in E. faecalis has yet to be explored. Here, we show that both hylA and hylB contribute to E. faecalis pathogenesis. In a CAUTI model, ΔhylA exhibited defects in bladder colonization and dissemination to the bloodstream, and ΔhylB exhibited a defect in kidney colonization. Furthermore, a ΔhylAΔhylB double mutant exhibited a severe colonization defect in a model of bacteremia while the single mutants colonized to a similar level as the wild-type strain, suggesting potential functional redundancy within the bloodstream. We next examined enzymatic activity, and demonstrate that HylB is capable of digesting both hyaluronic acid (HA) and chondroitin sulfate in vitro, while HylA exhibits only a very modest activity against heparin. Importantly, HA degradation by HylB provided a modest increase in cell density during the stationary phase and also contributed to dampening of lipopolysaccharide-mediated NF-κB activation. Overall, these data demonstrate that glycosaminoglycan degradation is important for E. faecalis pathogenesis in the urinary tract and during bloodstream infection.

Preferential catabolism of l- vs d-serine by Proteus mirabilis contributes to pathogenesis and catheter-associated urinary tract infection.

Proteus mirabilis is a common cause of urinary tract infection, especially in catheterized individuals. Amino acids are the predominant nutrient for bacteria during growth in urine, and our prior studies identified several amino acid import and catabolism genes as fitness factors for P. mirabilis catheter-associated urinary tract infection (CAUTI), particularly those for d- and l-serine. In this study, we sought to determine the hierarchy of amino acid utilization by P. mirabilis and to examine the relative importance of d- vs l-serine catabolism for critical steps in CAUTI development and progression. Herein, we show that P. mirabilis preferentially catabolizes l-serine during growth in human urine, followed by d-serine, threonine, tyrosine, glutamine, tryptophan, and phenylalanine. Independently disrupting catabolism of either d- or l-serine has minimal impact on in vitro phenotypes while completely disrupting both pathways decreases motility, biofilm formation, and fitness due to perturbation of membrane potential and cell wall biosynthesis. In a mouse model of CAUTI, loss of either serine catabolism system decreased fitness, but disrupting l-serine catabolism caused a greater fitness defect than disrupting d-serine catabolism. We, therefore, conclude that the hierarchical utilization of amino acids may be a critical component of P. mirabilis colonization and pathogenesis within the urinary tract.

A Novel Device-Integrated Drug Delivery System for Local Inhibition of Urinary Tract Infection.

Background: Catheter-associated urinary tract infection (CAUTI) is a frequent community-acquired infection and the most common nosocomial infection. Here, we developed a novel antimicrobial catheter concept that utilizes a silicone-based interpenetrating polymer network (IPN) as balloon material to facilitate a topical slow-release prophylaxis of antibacterial agents across the balloon to the urinary bladder.Methods: The balloon material was achieved by modifying low shore hardness silicone tubes with a hydrogel interpenetrating polymer in supercritical CO2 using the sequential method. Release properties and antibacterial efficacy of the IPN balloon treatment concept was investigated in vitro and in a porcine CAUTI model developed for the study. In the latter, Bactiguard Infection Protection (BIP) Foley catheters were also assessed to enable benchmark with the traditional antimicrobial coating principle.Results: Uropathogenic Escherichia coli was undetectable in urinary bladders and on retrieved catheters in the IPN treatment group as compared to control that revealed significant bacteriuria (>105 colony forming units/ml) as well as catheter-associated biofilm. The BIP catheters failed to prevent E. coli colonization of the bladder but significantly reduced catheter biofilm formation compared to the control.Conclusion: The IPN-catheter concept provides a novel, promising delivery route for local treatment in the urinary tract.

Self-Limiting Mussel Inspired Thin Antifouling Coating with Broad-Spectrum Resistance to Biofilm Formation to Prevent Catheter-Associated Infection in Mouse and Porcine Models.

Catheter-associated urinary tract infections (CAUTIs) are one of the most commonly occurring hospital-acquired infections. Current coating strategies to prevent catheter-associated biofilm formation are limited by their poor long-term efficiency and limited applicability to diverse materials. Here, the authors report a highly effective non-fouling coating with long-term biofilm prevention activity and is applicable to diverse catheters. The thin coating is lubricous, stable, highly uniform, and shows broad spectrum prevention of biofilm formation of nine different bacterial strains and prevents the migration of bacteria on catheter surface. The coating method is adapted to human-sized catheters (both intraluminal and extraluminal) and demonstrates long-term biofilm prevention activity over 30 days in challenging conditions. The coated catheters are tested in a mouse CAUTI model and demonstrate high efficiency in preventing bacterial colonization of both Gram-positive and Gram-negative bacteria. Furthermore, the coated human-sized Foley catheters are evaluated in a porcine CAUTI model and show consistent efficiency in reducing biofilm formation by Escherichia coli (E.coli) over 95%. The simplicity of the coating method, the ability to apply this coating on diverse materials, and the high efficiency in preventing bacterial adhesion increase the potential of this method for the development of next generation infection resistant medical devices.

Enterococcus faecalis Polymicrobial Interactions Facilitate Biofilm Formation, Antibiotic Recalcitrance, and Persistent Colonization of the Catheterized Urinary Tract.

Indwelling urinary catheters are common in health care settings and can lead to catheter-associated urinary tract infection (CAUTI). Long-term catheterization causes polymicrobial colonization of the catheter and urine, for which the clinical significance is poorly understood. Through prospective assessment of catheter urine colonization, we identified Enterococcus faecalis and Proteus mirabilis as the most prevalent and persistent co-colonizers. Clinical isolates of both species successfully co-colonized in a murine model of CAUTI, and they were observed to co-localize on catheter biofilms during infection. We further demonstrate that P. mirabilis preferentially adheres to E. faecalis during biofilm formation, and that contact-dependent interactions between E. faecalis and P. mirabilis facilitate establishment of a robust biofilm architecture that enhances antimicrobial resistance for both species. E. faecalis may therefore act as a pioneer species on urinary catheters, establishing an ideal surface for persistent colonization by more traditional pathogens such as P. mirabilis.

Ynt is the primary nickel import system used by Proteus mirabilis and specifically contributes to fitness by supplying nickel for urease activity.

Proteus mirabilis is a Gram-negative uropathogen and frequent cause of catheter-associated urinary tract infection (CAUTI). One important virulence factor is its urease enzyme, which requires nickel to be catalytically active. It is, therefore, hypothesized that nickel import is critical for P. mirabilis urease activity and pathogenesis during infection. P. mirabilis strain HI4320 encodes two putative nickel import systems, designated Nik and Ynt. By disrupting the substrate-binding proteins from each import system (nikA and yntA), we show that Ynt is the primary nickel importer, while Nik only compensates for loss of Ynt at high nickel concentrations. We further demonstrate that these are the only binding proteins capable of importing nickel for incorporation into the urease enzyme. Loss of either nickel-binding protein results in a significant fitness defect in a murine model of CAUTI, but YntA is more crucial as the yntA mutant was significantly outcompeted by the nikA mutant. Furthermore, despite the importance of nickel transport for hydrogenase activity, the sole contribution of yntA and nikA to virulence is due to their role in urease activity, as neither mutant exhibited a fitness defect when disrupted in a urease-negative background.

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.

(p)ppGpp and CodY Promote Enterococcus faecalis Virulence in a Murine Model of Catheter-Associated Urinary Tract Infection.

In Firmicutes, the nutrient-sensing regulators (p)ppGpp, the effector molecule of the stringent response, and CodY work in tandem to maintain bacterial fitness during infection. Here, we tested (p)ppGpp and codY mutant strains of Enterococcus faecalis in a catheter-associated urinary tract infection (CAUTI) mouse model and used global transcriptional analysis to investigate the relationship of (p)ppGpp and CodY. The absence of (p)ppGpp or single inactivation of codY led to lower bacterial loads in catheterized bladders and diminished biofilm formation on fibrinogen-coated surfaces under in vitro and in vivo conditions. Single inactivation of the bifunctional (p)ppGpp synthetase/hydrolase rel did not affect virulence, supporting previous evidence that the association of (p)ppGpp with enterococcal virulence is not dependent on the activation of the stringent response. Inactivation of codY in the (p)ppGpp0 strain restored E. faecalis virulence in the CAUTI model as well as the ability to form biofilms in vitro Transcriptome analysis revealed that inactivation of codY restores, for the most part, the dysregulated metabolism of (p)ppGpp0 cells. While a clear linkage between (p)ppGpp and CodY with expression of virulence factors could not be established, targeted transcriptional analysis indicates that a possible association between (p)ppGpp and c-di-AMP signaling pathways in response to the conditions found in the bladder may play a role in enterococcal CAUTI. Collectively, data from this study identify the (p)ppGpp-CodY network as an important contributor to enterococcal virulence in catheterized mouse bladder and support that basal (p)ppGpp pools and CodY promote virulence through maintenance of a balanced metabolism under adverse conditions.IMPORTANCE Catheter-associated urinary tract infections (CAUTIs) are one of the most frequent types of infection found in the hospital setting that can develop into serious and potentially fatal bloodstream infections. One of the infectious agents that frequently causes complicated CAUTI is the bacterium Enterococcus faecalis, a leading cause of hospital-acquired infections that are often difficult to treat due to the exceptional multidrug resistance of some isolates. Understanding the mechanisms by which E. faecalis causes CAUTI will aid in the discovery of new druggable targets to treat these infections. In this study, we report the importance of two nutrient-sensing bacterial regulators, named (p)ppGpp and CodY, for the ability of E. faecalis to infect the catheterized bladder of mice.

Urinary tract colonization is enhanced by a plasmid that regulates uropathogenic Acinetobacter baumannii chromosomal genes

Multidrug resistant (MDR) Acinetobacter baumannii poses a growing threat to global health. Research on Acinetobacter pathogenesis has primarily focused on pneumonia and bloodstream infections, even though one in five A. baumannii strains are isolated from urinary sites. In this study, we highlight the role of A. baumannii as a uropathogen. We develop the first A. baumannii catheter-associated urinary tract infection (CAUTI) murine model using UPAB1, a recent MDR urinary isolate. UPAB1 carries the plasmid pAB5, a member of the family of large conjugative plasmids that represses the type VI secretion system (T6SS) in multiple Acinetobacter strains. pAB5 confers niche specificity, as its carriage improves UPAB1 survival in a CAUTI model and decreases virulence in a pneumonia model. Comparative proteomic and transcriptomic analyses show that pAB5 regulates the expression of multiple chromosomally-encoded virulence factors besides T6SS. Our results demonstrate that plasmids can impact bacterial infections by controlling the expression of chromosomal genes.

DS86760016, a Leucyl-tRNA Synthetase Inhibitor with Activity against Pseudomonas aeruginosa.

DS86760016 is a new leucyl-tRNA-synthetase inhibitor at the preclinical development stage. DS86760016 showed potent activity against extended-spectrum multidrug-resistant Pseudomonas aeruginosa isolated from clinical samples and in vitro biofilms. In a murine catheter-associated urinary tract infection model, DS86760016 treatment resulted in significant eradication of P. aeruginosa from the kidney, bladder, and catheter without developing drug resistance. Our data suggest that DS86760016 has the potential to act as a new drug for the treatment of Pseudomonas infections.

Biofilm Assays on Fibrinogen-coated Silicone Catheters and 96-well Polystyrene Plates.

Biofilm formation is a well-known bacterial strategy that protects cells from hostile environments. During infection, bacteria found in a biofilm community are less sensitive to antibiotics and to the immune response, often allowing them to colonize and persist in the host niche. Not surprisingly, biofilm formation on medical devices, such as urinary catheters, is a major problem in hospital settings. To be able to eliminate such biofilms, it is important to understand the key bacterial factors that contribute to their formation. A common practice in the lab setting is to study biofilms grown in laboratory media. However, these media do not fully reflect the host environment conditions, potentially masking relevant biological determinants. This is the case during urinary catheterization, where a key element for Enterococcus faecalis and Staphylococcus aureus colonization and biofilm formation is the release of fibrinogen (Fg) into the bladder and its deposition on the urinary catheter. To recapitulate bladder conditions during catheter-associated urinary tract infection (CAUTI), we have developed a fibrinogen-coated catheter and 96-well plate biofilm assay in urine. Notably, enterococcal biofilm factors identified in these in vitro assays proved to be important for biofilm formation in vivo in a mouse model of CAUTI. Thus, the method described herein can be used to uncover biofilm-promoting factors that are uniquely relevant in the host environment, and that can be exploited to develop new antibacterial therapies.

Host and bacterial proteases influence biofilm formation and virulence in a murine model of enterococcal catheter-associated urinary tract infection

Enterococcus faecalis is a leading causative agent of catheter-associated urinary tract infection (CAUTI), the most common hospital-acquired infection. Its ability to grow and form catheter biofilm is dependent upon host fibrinogen (Fg). Examined here are how bacterial and host proteases interact with Fg and contribute to virulence. Analysis of mutants affecting the two major secreted proteases of E. faecalis OG1RF (GelE, SprE) revealed that while the loss of either had no effect on virulence in a murine CAUTI model or for formation of Fg-dependent biofilm in urine, the loss of both resulted in CAUTI attenuation and defective biofilm formation. GelE−, but not SprE− mutants, lost the ability to degrade Fg in medium, while paradoxically, both could degrade Fg in urine. The finding that SprE was activated independently of GelE in urine by a host trypsin-like protease resolved this paradox. Treatment of catheter-implanted mice with inhibitors of both host-derived and bacterial-derived proteases dramatically reduced catheter-induced inflammation, significantly inhibited dissemination from bladder to kidney and revealed an essential role for a host cysteine protease in promoting pathogenesis. These data show that both bacterial and host proteases contribute to CAUTI, that host proteases promote dissemination and suggest new strategies for therapeutic intervention.

Catheterization alters bladder ecology to potentiate Staphylococcus aureus infection of the urinary tract

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging cause of catheter-associated urinary tract infection (CAUTI), which frequently progresses to more serious invasive infections. We adapted a mouse model of CAUTI to investigate how catheterization increases an individual's susceptibility to MRSA UTI. This analysis revealed that catheterization was required for MRSA to achieve high-level, persistent infection in the bladder. As shown previously, catheter placement induced an inflammatory response resulting in the release of the host protein fibrinogen (Fg), which coated the bladder and implant. Following infection, we showed that MRSA attached to the urothelium and implant in patterns that colocalized with deposited Fg. Furthermore, MRSA exacerbated the host inflammatory response to stimulate the additional release and accumulation of Fg in the urinary tract, which facilitated MRSA colonization. Consistent with this model, analysis of catheters from patients with S. aureus-positive cultures revealed colocalization of Fg, which was deposited on the catheter, with S. aureus Clumping Factors A and B (ClfA and ClfB) have been shown to contribute to MRSA-Fg interactions in other models of disease. We found that mutants in clfA had significantly greater Fg-binding defects than mutants in clfB in several in vitro assays. Paradoxically, only the ClfB- strain was significantly attenuated in the CAUTI model. Together, these data suggest that catheterization alters the urinary tract environment to promote MRSA CAUTI pathogenesis by inducing the release of Fg, which the pathogen enhances to persist in the urinary tract despite the host's robust immune response.

The Pathogenic Potential of Proteus mirabilis Is Enhanced by Other Uropathogens during Polymicrobial Urinary Tract Infection

Urinary catheter use is prevalent in health care settings, and polymicrobial colonization by urease-positive organisms, such as Proteus mirabilis and Providencia stuartii, commonly occurs with long-term catheterization. We previously demonstrated that coinfection with P. mirabilis and P. stuartii increased overall urease activity in vitro and disease severity in a model of urinary tract infection (UTI). In this study, we expanded these findings to a murine model of catheter-associated UTI (CAUTI), delineated the contribution of enhanced urease activity to coinfection pathogenesis, and screened for enhanced urease activity with other common CAUTI pathogens. In the UTI model, mice coinfected with the two species exhibited higher urine pH values, urolithiasis, bacteremia, and more pronounced tissue damage and inflammation compared to the findings for mice infected with a single species, despite having a similar bacterial burden within the urinary tract. The presence of P. stuartii, regardless of urease production by this organism, was sufficient to enhance P. mirabilis urease activity and increase disease severity, and enhanced urease activity was the predominant factor driving tissue damage and the dissemination of both organisms to the bloodstream during coinfection. These findings were largely recapitulated in the CAUTI model. Other uropathogens also enhanced P. mirabilis urease activity in vitro, including recent clinical isolates of Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, and Pseudomonas aeruginosa We therefore conclude that the underlying mechanism of enhanced urease activity may represent a widespread target for limiting the detrimental consequences of polymicrobial catheter colonization, particularly by P. mirabilis and other urease-positive bacteria.

Cyclic Di-GMP Signaling Contributes to Pseudomonas aeruginosa-Mediated Catheter-Associated Urinary Tract Infection.

Bis-(3'-5') cyclic dimeric GMP (c-di-GMP) controls the lifestyle transition between the sessile and motile states in many Gram-negative bacteria, including the opportunistic human pathogen Pseudomonas aeruginosa. Under laboratory conditions, high concentrations of c-di-GMP decrease motility and promote biofilm formation, while low concentrations of c-di-GMP promote motility and decease biofilm formation. Here we sought to determine the contribution of c-di-GMP signaling to biofilm formation during P. aeruginosa-mediated catheter-associated urinary tract infection (CAUTI). Using a murine CAUTI model, a decrease in CFU was detected in the bladders and kidneys of mice infected with strains overexpressing the phosphodiesterases (PDEs) encoded by PA3947 and PA2133 compared to those infected with wild-type P. aeruginosa. Conversely, overexpression of the diguanylate cyclases (DGCs) encoded by PA3702 and PA1107 increased the number of bacteria in bladder and significantly increased dissemination of bacteria to the kidneys compared to wild-type infection. To determine which of the DGCs and PDEs contribute to c-di-GMP signaling during infection, a panel of PA14 in-frame deletion mutants lacking DGCs and PDEs were tested in the CAUTI model. Results from these infections revealed five mutants, three containing GGDEF domains (ΔPA14_26970, ΔPA14_72420, and ΔsiaD) and two containing dual GGDEF-EAL domains (ΔmorA and ΔPA14_07500), with decreased colonization of the bladder and dissemination to the kidneys. These results indicate that c-di-GMP signaling influences P. aeruginosa-mediated biofilms during CAUTI. Biofilm-based infections are an important cause of nosocomial infections, since they resist the immune response and traditional antibiotic treatment. Cyclic di-GMP (c-di-GMP) is a second messenger that promotes biofilm formation in many Gram-negative pathogens, including Pseudomonas aeruginosa. Here we determined the contribution of c-di-GMP signaling to catheter-associated urinary tract infection (CAUTI), an animal model of biofilm-based infection. P. aeruginosa with elevated levels of c-di-GMP during the initial infection produces an increased bacterial burden in the bladder and kidneys. Conversely, low concentrations of c-di-GMP decreased the bacterial burden in the bladder and kidneys. We screened a library of mutants with mutations in genes regulating c-di-GMP signaling and found several mutants that altered colonization of the urinary tract. This study implicates c-di-GMP signaling during CAUTI.

Catheter-Associated Urinary Tract Infection by Pseudomonas aeruginosa Is Mediated by Exopolysaccharide-Independent Biofilms

Pseudomonas aeruginosa is an opportunistic human pathogen that is especially adept at forming surface-associated biofilms. P. aeruginosa causes catheter-associated urinary tract infections (CAUTIs) through biofilm formation on the surface of indwelling catheters. P. aeruginosa encodes three extracellular polysaccharides, PEL, PSL, and alginate, and utilizes the PEL and PSL polysaccharides to form biofilms in vitro; however, the requirement of these polysaccharides during in vivo infections is not well understood. Here we show in a murine model of CAUTI that PAO1, a strain harboring pel, psl, and alg genes, and PA14, a strain harboring pel and alg genes, form biofilms on the implanted catheters. To determine the requirement of exopolysaccharide during in vivo biofilm infections, we tested isogenic mutants lacking the pel, psl, and alg operons and showed that PA14 mutants lacking these operons can successfully form biofilms on catheters in the CAUTI model. To determine the host factor(s) that induces the ΔpelD mutant to form biofilm, we tested mouse, human, and artificial urine and show that urine can induce biofilm formation by the PA14 ΔpelD mutant. By testing the major constituents of urine, we show that urea can induce a pel-, psl-, and alg-independent biofilm. These pel-, psl-, and alg-independent biofilms are mediated by the release of extracellular DNA. Treatment of biofilms formed in urea with DNase I reduced the biofilm, indicating that extracellular DNA supports biofilm formation. Our results indicate that the opportunistic pathogen P. aeruginosa utilizes a distinct program to form biofilms that are independent of exopolysaccharides during CAUTI.

Gene expression of Pseudomonas aeruginosa and MRSA within a catheter-associated urinary tract infection biofilm model

Catheter-associated urinary tract infections (CAUTI) have frequently been studied in monocultures in vitro. However, many CAUTI are due to the presence of a mixed microbial community and not just a single population, especially within patients subjected to long-term catheterization. This can potentially have important clinical implications in regards to treatment strategy and outcome. This study revealed that when Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) (both commonly found in CAUTI) were grown together as a mixed culture within a CAUTI model in comparison to their respective monocultures, accelerated biofilm development was observed. Virulence gene expression analysis within P. aeruginosa and MRSA monoculture and mixed biofilms was performed through use of real-time quantitative PCR. It was revealed that production of P. aeruginosa exotoxin A was increased 1839-fold when P. aeruginosa and MRSA were grown together as a mixed biofilm. Significant expression of α-haemolysin by MRSA was not observed in either culture. It is proposed that both the biofilm-forming capability and virulence gene expression of microbes within CAUTI mixed biofilms may differ substantially to the respective microbial monocultures. This highlights the importance of developing specific treatment strategies for CAUTI when polymicrobial communities are present.

Therapeutic Efficacy of Sitafloxacin Against Pseudomonas aeruginosa in a Rat Model of Urinary Tract Infection

Biofilm-forming bacteria on the surface of the urinary catheter cause major concern in hospitalised patients because they are refractory to antibacterial chemotherapy. Pseudomonas aeruginosa is a leading cause of nosocomial infections including catheterassociated urinary tract infection (UTI). Sitafloxacin (DU-6859a), a fluoroquinolone with potent activity against P. aeruginosa, has a good pharmacokinetic profile with high oral absorption and high urinary recovery. We established a rat model of catheterassociated UTI with P. aeruginosa, in which persistent ascending infection is induced by growing the organism in biofilm on the surface of the catheter segment inserted into the bladder. The therapeutic effect of sitafloxacin on the catheter-associated UTI model was examined and compared with that of ciprofloxacin, gentamicin and meropenem.

Therapeutic Efficacy of Fleroxacin for Eliminating Catheter-Associated Urinary Tract Infection in a Rabbit Model

The efficacy of fleroxacin as therapy for experimentally induced catheter-associated urinary tract infection (CAUTI) was examined. A rabbit model of CAUTI using a closed urinary catheter drainage system and the mutant strain of Escherichia coli (WE 6933) were used to examine three dosage regimens (30 mg/kg q8h i.v.; 20 mg/kg q8h i.v.; and 10 mg/kg q8h++i.v.) of fleroxacin administered intravenously for 4 days. Quantitative bacterial counts, urinary concentrations of fleroxacin and desmethylferoxacin, histopathologic changes, and electron microscopic evaluation of catheter-associated biofilm and mucosal biofilm were performed. The results indicated that the bacterial biofilm on the urinary catheter could be eliminated by fleroxacin at 30 mg/kg q8h i.v. and 20 mg/kg q8h i.v. Fleroxacin concentrations in urine exceeded the levels necessary to destroy E. coli. Viable bacteria were eliminated with the third regimen (10 mg/kg q8h i.v.), but electron microscopy demonstrated remnants of bacterial biofilm. Histopathologic changes were significantly reduced in all fleroxacin-treated rabbits, and scanning electron microscopy showed deterioration of the bacterial biofilm on the surface of the Foley catheter in treated animals. These data suggest that fleroxacin may be useful for treating catheter-related infections because these therapeutic dosages limited ascending infections of the urethra and bladder, eliminated catheter-associated biofilms, and killed planktonic bacteria in urine.

Amdinocillin treatment of catheter-associated bacteriuria in rabbits.

The effect of the beta-lactam antibiotic, amdinocillin, on the bacterial biofilm adherent to the Foley catheter surface, the bacterial microcolonies attached to the urinary bladder mucosa, and on planktonic bacteria in the urine was studied in a rabbit model of the closed urinary catheter drainage system. Progressively increasing the dose of antibiotic in this experimental catheter-associated urinary tract infection model first eliminated the bacterial population adherent to the bladder mucosa and then the planktonic population in the urine. The bacterial biofilm on the Foley catheter could be eradicated only by the highest dose of antibiotic (400 mg/kg). Scanning electron microscopy showed a gradual deterioration of bacterial biofilm and reduction in bacterial numbers with increasing antibiotic dosages. These data suggest that antibiotics used in short-term catheterization may reduce the serious sequelae associated with catheter-related infections by clearing the potentially dangerous bladder mucosal bacterial populations and urine planktonic bacteria.