Electron microscopic study of an infected Foley catheter

A scanning and transmission electron microscopic study was made of material from the surface of a Foley catheter removed from an 87-year-old woman with antibiotic-resistant bacteriuria. A thick, adherent bacterial biofilm was found. The sessile adherent bacteria were surrounded by an extensive exopolysaccharide glycocalyx that appears to be fundamental in the pathogenesis of catheter-associated urinary tract infections and their resistance to systemic antibiotic therapy.     

Catheter-associated urinary tract infections

In the past few years it has been clearly demonstrated that the concept of bacterial biofilm production permits an understanding and provides some explanation of the pathogenesis, diagnosis and treatment of catheter-associated urinary tract infections. This concept describes the colonization of catheter surfaces and the movement of bacteria against the urinary flow. It explains the antibacterial resistance of these matrix-enclosed sessile populations of bacteria. The catheter encrustation can be observed as mineralizing bacterial biofilm. The differentiation in swarming cells exposing a much higher activity of the enzyme urease is responsible for the predominant role of Proteus mirabilis in obstructing encrustations. The guidelines for the prevention of catheter-associated urinary tract infections were developed over the past decades by clinicians and are still valid. They can now be better understood taking into consideration these new theories. As overuse of urethral catheters and non-compliance of their recommended use are still apparent, educational and surveillance programmes are needed to help maintain good standards of care.     

The development of bacterial biofilms on indwelling urethral catheters

The biofilm mode of growth has been implicated in the majority of human bacterial infections. In the urinary tract, notable biofilm-associated infections include prostatitis, chronic cystitis, struvite urolithiasis, and catheter-associated infections. Biofilms protect the causative organisms from host defences and antimicrobial therapy. Biofilm formation has traditionally been considered to result from adhesion and capsule formation by adherent microorganisms. Recent work has shown that a large number of genes are activated during this process, some of which have been associated with twitching motility, quorum sensing, and slow growth. In this paper, we review some of the recent work on biofilm biology and highlight its role in urinary tract infections, particularly those associated with urinary catheters.     

Catheter-associated and nosocomial urinary tract infections: antibiotic resistance and influence on commonly used antimicrobial therapy

The objective is to evaluate resistance between community-acquired urinary tract infections (CAUTI), nosocomialy-acquired urinary tract infections (NAUTI), and empirical therapy adequacy. E. coli is the predominant pathogen of both CAUTI and NAUTI, followed by Klebsiella spp. in NAUTI and Pseudomonas spp. in catheter-associated urinary tract infections. The highest level of general resistance was found among isolates of NAUTI and catheter-associated UTI followed by CAUTI isolates. Absolute or high level resistance for commonly used empirical antimicrobial therapy was found in catheter-associated UTI and NAUTI while resistance among CAUTI was respectable. Patients with NAUTI as well as patients with catheter-associated urinary tract infections have similar resistance and similar microorganisms isolated as a causative agents, and should not be empirically treated unless the clinical emergency requests.     

Adherence of gram-negative uropathogens to human uroepithelial cells

The adherence of several gram-negative uropathogens to human uroepithelial cells was examined with scanning and transmission electron microscopy, and in vitro adhesion assays. The bacteria studied demonstrated different extracellular structures: fimbria and glycocalyx. Human uroepithelial cells were obtained from a bladder tumor cell line (T-24) and from different groups of patients, including those with no history of urinary tract infection (controls), recurrent urinary tract infection, acute cystitis and bladder tumors before and after bacillus Calmette-Guerin therapy. Results from these comparative studies showed that bacteria with extracellular structures adhered better than those bacteria without extracellular structures. It also was shown that uroepithelial cells obtained from patients with recurrent urinary tract infection and with acute cystitis were more susceptible to bacterial adherence than the uroepithelial cells of the controls (there were significant increases of 2 to 5-fold in mean adherence in the former 2 groups, p equals 0.015 and 0.002). There was no significant difference in bacterial adherence between the T-24 cells and the bladder tumor cells before bacillus Calmette-Guerin treatment. However, in both groups after treatment with bacillus Calmette-Guerin the mean adherence increased 2 to 4-fold (p equals 3 times 10(-5)). A survey of 29 bladder tumor patients also showed a 5-fold increase in the incidence of acquired urinary tract infection after bacillus Calmette-Guerin therapy. These results reveal a correlation between bacterial adherence and urinary tract infection, and suggest that bacterial adherence to uroepithelial cells depends upon the bacterial extracellular structures and the source of the uroepithelial cells.     

Prophylactic efficacy of a new gentamicin-releasing urethral catheter in short-term catheterized rabbits

OBJECTIVE: To describe an indwelling urethral catheter coated with gentamicin sulphate on the inner and outer surface of the catheter, and to evaluate the efficacy and safety of this catheter in preventing catheter-associated infections in rabbits. Materials and methods Sixty rabbits were divided equally into control and experimental groups which were then subdivided equally according to the duration of catheterization (1, 3 and 5 days). Silicone-treated latex catheters were used in the control group and gentamicin-releasing catheters in the experimental group. Urine samples and surface swabs from the catheter were cultured for bacteriological assessment, and the catheter surface examined by scanning electron microscopy to structurally analyse the biofilms. RESULTS: The gentamicin-releasing catheter reduced the incidence of bacteriuria (defined as > or = 100 c.f.u./mL) after both 3 and 5 days of catheterization (eight and 10 rabbits, respectively, for the control catheter, vs two and four rabbits for the gentamicin-releasing catheter, P < 0.05). The surfaces of the gentamicin-releasing catheter were colonized less often than those of the control catheter after both 3 and 5 days (eight and 10, respectively, for the control, vs one and four for the gentamicin-releasing catheter, P < 0.05). Scanning electron microscopy showed the formation of bacterial biofilm throughout the 3-day and 5-day control catheters, but deterioration of the bacterial biofilm was visible on the surface of the gentamicin-releasing catheters. CONCLUSION: This new gentamicin-releasing catheter produced an antibacterial barrier which inhibited catheter-associated urinary tract infection with no toxicity for at least 5 days. These in vivo studies suggest that this new catheter may be useful for controlling infection, with systemic and local safety, in patients undergoing short-term indwelling urethral catheterization.     

Bacteriological and architectural studies of infected stones

The stones associated with urinary tract infection were cultured using a method to distinguish between surface contamination and bacteria within the stone. Twenty three of 30 stones (77%) were infected mainly by Proteus mirabilis or Pseudomonas aeruginosa and most were composed of struvite and/or apatite. Most oxalate and uric acid stones were sterile; occasionally the stones with positive culture had a non-urea-splitting bacteria and these were thought to have been infected secondarily. Some infected stones were studied by light microscopy scanning election microscopy and transmission electron microscopy. We found many rods in the interstices of crystals of struvite and apatite extensively from the nucleus to peripheral layers. These findings are important in the prevention and treatment of infection stones.     

Phytohemagglutinin lymphocyte stimulation in children with recurrent urinary tract infections

The delayed hypersensitivity (T cell) response of children with recurrent urinary tract infections, normal children, and children with other bacterial infections was measured by the ability of their lymphocytes to react in vitro to phytohemagglutinin. A comparison among these three groups demonstrated no differences in response. We conclude that the delayed hypersensitivity response is grossly normal in most children with recurrent urinary tract infections.     

Scanning electron microscopy of human urine and purified Tamm-Horsfall's glycoprotein

Dialyzed and dehydrated human urine and purified Tamm-Horsfall's glycoprotein revealed similar morphology by scanning electron microscopy. Single filaments, with diameters between 15-45 nm, splitting off and merging with thicker fibers at irregular intervals made up a three-dimensional meshwork with submicrometer pores. The resulting "fishing net" is capable of trapping microorganisms and may facilitate their elimination from the urinary tract by micturition. Tamm-Horsfall's glycoprotein may accordingly be a factor protecting against urinary tract infections.     

Sinnvolle und nicht sinnvolle Hygienemaßnahmen in der Urologie

In urology, catheter-associated urinary tract infections are most common, and postoperative wound infections the second most common nosocomial infections. This article gives an overview of standard hygiene measures, but focuses on proven and unproven hygiene measures for preventing catheter-associated urinary tract infections and postoperative wound infections. Consistent implementation of these measures contributes to minimizing infection rates and to establishing a quality standard, whereby surveillance of nosocomial infections contributes substantially to internal quality assurance.     

The anti-adherence effect of heparin: A visual analysis

The various intrinsic bladder mucosal defenses against bacterial invasion, including the anti-adherence action of the surface mucopolysaccharide layer, have been documented in recent years. Studies have suggested Heparin, a mucopolysaccharide, may have anti-adherence action. We used scanning electron microscopy to visually evaluate the effects of intravesical HCl, Heparin and Protamine on the interaction between E. coli and rat bladders. Our findings concurred with previous statistical analyses using radio-isotope labelled bacteria, suggesting a beneficial anti-adherence effect of Heparin which can be negated by Protamine. We also noted a white coating on the bacteria in bladders treated with Heparin. We suggest this may represent minute amounts of Heparin coating the bacteria, thus decreasing bacterial adherence to bladder mucosa. Analogues of Heparin, without anti-coagulant properties, may be useful in prophylaxis against urinary tract infections.     

Clinical studies and morphological response on ST-95 (fosfomycin)

Clinical effects of ST-95 (fosfomycin) on infections of the urinary tract were studied on the basis of morphological changes of the urinary bacteria. The subjects were 22 inpatients with complex infections of the urinary tract. ST-95 was dissolved in physiologic saline (2 g/100 ml) and administered intravenously by drip infusion over a 1-hour period twice daily for 5 days. According to the UTI criteria, the treatment was effective in 13 (81%) of the 16 evaluable cases. The present effectiveness in 8 patients with chronic catheterization was 75%. No side effects were observed in any patient. Among the laboratory data, GOT and GPT were slightly increased in 1 patient, but their relations with the treatment were unknown. In one patient (P. vulgaris; MIC: 12.5 micrograms/ml), changes in the urinary ST-95 concentration, viable bacterial count, and morphology of the bacteria were studied after the initial administration. The urinary viable cell count was 1.5 x 10(7) cells/ml before administration, but it was reduced to 1.6 x 10(4) cells/ml at the end of the 1-hour infusion, and decreased progressively thereafter to complete disappearance after 12 hours. Under differential interference microscopy, filamentous debris of bacteria and spherical bacteria with irregular surface were observed from immediately after the end of the administration. By transmission electron microscopy, the cell wall showed a number of projections with formation of vacuolar structures in the space between the cell wall and the irregularly-shaped cytoplasms. In conclusion, the results of administration of ST-95 in complex infections of the urinary tract were satisfactory. The morphological changes of the bacteria suggested that this agent acts at an early stage of cell wall synthesis.     

In vitro quantitative adherence of bacteria to intravascular catheters

Adapting standard techniques, a simple in vitro system was devised to compare quantitative bacterial adherence to iv catheters of different compositions. Upon brief immersion of catheters in suspensions of Staphylococcus aureus, coagulase-negative staphylococci, and Escherichia coli, organisms adhered to catheter surfaces. After overnight growth in broth, organisms remained adherent and formed colonies, as shown by light and scanning electron microscopy. In addition, quantitative adherence using a blood agar roll technique, expressed as bacteria per square centimeter of catheter surface area per 10(6) colonies per milliliter inoculum, was calculated. Adherence was greater on polyvinylchloride (PVC) catheters (geometric mean 342) than on Teflon catheters (geometric mean 49.6) for coagulase-negative staphylococci (P less than 0.005). Also, the number of coagulase-negative staphylococci adherent to PVC catheters was significantly greater than for E. coli (geometric mean 70.6) at analogous inocula (P less than 0.02). Differences in bacterial adherence to the surface of iv devices may be important in the pathogenesis of catheter-associated infections. This in vitro method could prove useful in testing bacterial adherence properties of newly developed catheter materials, and allow development of catheters less prone to be associated with bacterial adherence and catheter-related infections.     

细菌生物膜对尿管相关性尿路感染的影响

目的 探讨细菌生物膜对留置尿管相关性尿路感染的影响。方法 对留置尿管不同时间的43例患者，于撤除尿管时行尿液细菌培养，并采用阿利新蓝-刚果红联合染色和扫描电镜观察尿管细菌生物膜形成情况，分析尿管细菌生物膜形成与尿管细菌培养及抗生素应用情况的关系。结果 留置尿管患者尿管细菌生物膜阳性率，3d组为0（0／4），1周组33．3％（4／12），2周组71．4％（10／14），4周组100．0％（13／13）。应用抗生素组60．6％（20／33），未用抗生素组70．0％（7／10），2组差异无统计学意义，P〉0．05。结论 细菌生物膜形成是留置尿管相关性尿路感染的重要致病因素，抗生素预防治疗效果不明显。缩短尿管留置时间，采用封闭式引流等仍是尿路感染主要的防治方法。     

妊娠期尿路感染相关因素及临床防治

目的了解妊娠期尿路感染的危险因素、主要病原菌及敏感抗生素,以提高诊治水平。方法选取2008年1月至2014年1月在我院住院的106例妊娠合并尿路感染患者,并选取产科门诊进行产前检查的无尿路感染的孕妇126例进行回顾性研究。结果年龄、孕周、糖尿病、既往尿路感染、泌尿系结石、贫血、流产是妊娠期尿路感染的高危因素,文化程度与妊娠期的尿路感染相关。妊娠期尿路感染病原菌以大肠埃希菌为主（占60．3％）。革兰阴性杆菌对青霉素类及喹诺酮类抗生素耐药率高,对头孢呋辛、头孢唑林、头孢他啶、头孢哌酮、头孢吡肟、亚胺培南、呋哺妥因敏感。革兰阳性球菌对半合成青霉素、喹诺酮类耐药率较高,对头孢呋辛、头孢唑林、头孢他啶、头孢哌酮、头孢吡肟、亚胺培南、呋喃妥因敏感。结论应注意妊娠期尿路感染的高危因素,加强孕期尿液检查及中段尿培养检查,选用敏感、合理的抗菌素治疗。     

Catheter-associated bacteriuria. An experimental study

A bacteriologically-stressed catheterized animal model was developed to evaluate the comparative importance of the intraluminal versus the extraluminal route of catheter-acquired urinary tract infections. This study indicated that in short-term catheterization (less than 7 days), contamination of the drainage spout or accidental disconnection of the drainage tube resulted in bacteriuria within a short time (32-48 hours). If a strict sterile closed drainage system was maintained, the extraluminal route assumed more importance in the development of bacteriuria, however this pathway was considerably slower (72-168 hours). It appeared that catheter-associated bacteriuria results from ascending bacterial colonization within glycocalyx-enclosed biofilm on the inside and/or outside surfaces of the catheter and drainage systems. Development of a biomaterial that inhibits bacterial adherence and does not allow upstream colonization of bacteria on the catheter drainage system would significantly influence the rate of catheter-acquired urinary tract infection.     

Bacterial colonization of percutaneous sutures

The direct electron microscopic examination of 15 sutures and 15 staples removed from 10 healed surgical wounds showed, on the intradermal portions, consistent colonization by bacteria growing in adherent biofilms. This clearly demonstrable bacterial colonization of biomaterials within the wound tract had not resulted in infection or perceptible inflammation in any of the wounds. These bacterial cells were of several morphotypes, including gram-positive cocci, and all specimens yielded cultures of the autochthonous (native) skin bacterium, Staphylococcus epidermidis. The bacteria within the wound tracts were enveloped by extracellular material that appeared on scanning electron microscopy to be a condensed amorphous residue and on transmission electron microscopy to be a fibrous extracellular matrix. We suggest that this mode of growth, in which the colonizing bacteria are enveloped in a copious exopolysaccharide glycocalix, protects the bacteria from host defense factors and accounts for their persistence on the suture surfaces until they are removed with the sutures.     

Catheter-associated urinary tract infection therapy by bladder irrigation — Success or washout?

The sterility of the urinary tract is maintained in part by the outflow of urine which prevents pathogenic organisms from ascending into the bladder. The use of a urinary catheter in a patient's management impairs this protective mechanism. Prolonged usage increases the risk of infection. A variety of techniques and irrigation fluids have been used to prevent or treat catheter-associated urinary tract infections (UTI) caused by bacteria and certain fungi. Despite promising results, the efficacy of bladder irrigation has been limited by toxic effects of the solutions used and the development of bacterial resistance. When catheterization is essential it should be for a limited period, allied to careful patient and catheter hygiene. In long term catheterization, catheter blockages may be cleared by intermittent irrigation using sterile saline. Although the use of amphotericin irrigation is effective in treating candidal UTI, the use of bladder irrigation in bacterial UTI remains controversial.     

Potential contribution of optional urease-positive bacteria to idiopathic urinary calcium stone formation

We investigated the effects of weak to moderate urease hydrolysis by optional urease-positive microorganisms in an artificial urine model enriched with calcium phosphate and calcium oxalate in respect of calcium stone formation. The incubation experiments were performed using a discontinuously running fermenter device to simulate the urinary system. The kinetics of cell division rates, pH and ammonium ion production were measured and correlated to crystallite appearance in the incubation medium. Qualitative analyses of the sediments revealed apatite. Investigations using light microscopy and scanning electron microscopy (SEM) confirmed the matrix effect of bacterial glycoproteins. It was shown that initiation of calcium oxalate stone formation is in all probability equally determined by matrix effects and by heteronuclear crystailization if the urinary tract is infected by optional urease-positive bacteria. When urinary inorganic phosphate is present, calcium phosphate nidi are always initially formed, and may subsequently be coated by calcium oxalate.     

Experimental study of gastrointestinal mucopathy after severe burns]

Changes in gastrointestinal tract mucous membrane after serious burns were studied with light microscopy, transmission electron microscopy and scanning electron microscopy. The results showed that changes in the gastrointestinal tract mucous membrane included not only erosions and ulcers, but also mucoid necrosis and bacterial translocation. The injuries of the intestinal mucous membrane began from the apex of villi. There are epithelial necrosis, with desquamation and exposure of villi. The injuries are much more serious and extensive than that of gastric mucous membrane, especially in the jejunum. These results suggested that after serious burns, not only there were stress ulcers of the gastroduodenum, but the whole gastrointestinal tract was involved.