Adherence to urethral catheters by bacteria causing nosocomial infections

Is otitis media with effusion a biofilm infection?

Recent attention has focused on the possibility that otitis media with effusion (OME) may represent a chronic infective state such as those evidenced in conditions secondary to biofilms or small colony variants. This review discusses the evidence suggesting that this may indeed be the case and explains why this may prove to be important in the future management of this condition by discussing recent advances in understanding these bacterial phenotypic variants.

PDMS-based polyurethanes with MPEG grafts: mechanical properties, bacterial repellency, and release behavior of rifampicin

PDMS-based polyurethanes (PUs) grafted with monomethoxy poly(ethylene glycol) (MPEG) were synthesized to develop a coating material for urinary catheters with a silicone surface for minimizing urinary tract infections. MPEG was grafted on PDMS-based PUs by two methods depending on the PU synthetic routes: esterification and allophanate reactions. It was confirmed from mechanical characterization that an increase of the hard segment amount enhanced the ultimate strength and Young's modulus, while reducing elongation at the end-points. The incorporation of MPEG in PDMS-based PUs induced a decrease in tensile strength and Young's modulus, and increased elongation at the break point due to its high flexibility. When hydrated in distilled water, mechanical properties of all PUs synthesized in this study deteriorated due to water absorption. It was evident from the bacterial adhesion test that PDMS-based PUs showed moderate resistance to adhesion of E. coli on their surfaces compared to Pellethane, while the incorporation of MPEG significantly enhanced repellency to bacteria, including E. coli and S. epidermidis. We also studied the release behavior of an antibiotic drug, rifampicin, from the polymeric devices fabricated by solvent evaporation. Although rifampicin is hydrophilic and soluble in pH 7.4 phosphate buffer, it showed a sustained release over 45 days from PDMS-based PUs with MPEG that were grafted on ethylene glycol residues by allophanate reaction. This release characteristic was predominantly influenced by a hydrogen bond interaction between the polymers and rifampicin, which was confirmed through an ATR-IR study. This may imply that the specific interaction is responsible for the delayed release. Considering the mechanical properties, morphologies of drug-incorporated polymeric matrices, and drug release behaviors, PDMS-based PU with MPEG that were grafted on ethylene glycol (a chain extender) residues by allophanate reaction showed better material properties for uretharal catheter coating pusposes in order to minimize urinary tract infections.

Urinary catheters: selection, management and prevention of infection

Urinary catheterization is a common procedure for both hospital and community patients. Nurses make many of the decisions in regard to both catheter selection and subsequent catheter care. These decisions, for example, in the type of catheterization (intermittent, indwelling, urethral or suprapubic) should be made on an informed basis. Choosing the optimum catheter material and size can benefit catheter care. Encrustation can be a problem for some catheterized patients and nurses are often involved in trying to prevent or treat it. This and other aspects of catheter management including infection control, constipation and meatal hygiene are discussed.

Hydrogel/silver ion-coated urinary catheter reduces nosocomial urinary tract infection rates in intensive care unit patients: a multicenter study

OBJECTIVES

Indwelling urinary catheters are the leading source of nosocomial urinary tract infections (NUTIs). The Bardex I.C. catheter is a hydrogel latex Foley catheter with a monolayer of silver metal applied to the inner and outer surfaces of the catheter. We investigated the Bardex I.C. catheter for its ability to decrease the NUTI rate in critical care units.

METHODS

Five hospitals participated in a blind prospective study, exchanging the standard latex Foley catheter for the Bardex I.C. Foley catheter. The device use rate and NUTI rate were monitored. Data were collected and analyzed using Wilcoxon rank sum test and four-way analysis of variance. A cost analysis was also performed.

RESULTS

The baseline period, intervention period, and number of device days was similar for both periods. The unadjusted catheter-associated infection rate during the baseline and intervention periods was 7.1 and 4.5 infections per 1000 catheter days, respectively (P <0.01). The adjusted catheter-associated infection rate during the baseline and intervention periods was 8.1 and 4.9 infections per 1000 catheter days, respectively. This was not statistically significant (P = 0. 13).

CONCLUSIONS

A trend toward a reduction in NUTIs with the use of the hydrogel/silver-coated catheter was noted in all intensive care units at each institution as shown by the unadjusted and adjusted catheter-associated infection rates. One hospital demonstrated a statistically significant reduction in NUTIs. However, statistical significance was not met when the results were adjusted. The cost analysis at one institution demonstrated cost savings with the use of the silver-coated catheter. Future analysis may require a double-blind, prospective-controlled study of longer duration to reach statistical significance.

Microbial biofilms: their development and significance for medical device-related infections

Microbial adhesion and biofilm formation on medical devices represent a common occurrence that can lead to serious illness and death. The process by which bacteria and yeast colonize open and closed implants is fairly complicated and involves a series of steps commencing with deposition of host substances onto the material. Prevention and treatment of established biofilms with antimicrobial agents are difficult because the organisms are encased within a protected microenvironment. Efforts to reduce adhesion using specially developed materials, such as hydrophilic or heparin coated, have had modest success once applied to the patient. The reason, at least for the most part, is the diverse milieu into which devices are placed and the multitude of ways in which organisms can colonize surfaces. A better understanding of the process is required, and the knowledge gained must be used to devise new strategies as alternatives to the traditional employment of antibiotics. These new approaches may still use antibiotics but at different concentrations (low to prevent and high to treat infection) and in a different manner (perhaps spiked therapy in which there is a delay between doses to reduce the risk of drug resistance and impact on normal flora). The possibility of applying functional foods to patient management should also be pursued.

Urinary catheters: selection, maintenance and nursing care

Catheterization is often undertaken without sufficient assessment, and the high rates of bacteriuria (10-20%) occurring in catheterized patients seem to be accepted (Ward et al, 1997). This article reviews catheter selection, maintenance and nursing care, highlighting problem areas and suggesting measures that may be taken to reduce the risk factors. A problem-solving approach, based on research evidence relating to catheter care, is presented. Often there is a simple solution to a problem, but treatments based on traditions or myths appear to be the first choice in many situations. This article aims to provide nurses with the evidence base required to establish and maintain a urinary drainage system safely.

In vitro adherence of Pseudomonas aeruginosa to four intraocular lenses

PURPOSE

To compare the relative degrees of adherence of a clinical strain of Pseudomonas aeruginosa to the optic material of four intraocular lenses (IOLs).

SETTING

Center for Applied and Environmental Microbiology, Georgia State University, Atlanta, Georgia, USA.

METHODS

Intraocular lens optics made of poly(methyl methacrylate) (PMMA), AcrySof-acrylic, and silicone were included in this study. The IOLs were incubated in a minimal medium with cells of P. aeruginosa for 2 hours and 18 hours. Cells in the 2 hour experiment were prelabeled with 3H-leucine; those in the 18 hour experiments were postlabeled. After rinsing the IOLs to remove loosely adherent cells, we determined the number of cells adhered to coded lenses from calibration curves of disintegrations per minute versus cells per square millimeter. Additional lenses were incubated with P. aeruginosa and examined with scanning electron microscopy.

RESULTS

The adherence of P. aeruginosa in order of increasing magnitude was AcrySof-acrylic < PMMA < silicone 1 < silicone 2. The differences between all groups were statistically significant. The scanning electron microscopy observations were in general agreement with the radiolabel studies.

CONCLUSIONS

The AcrySof-acrylic IOL was less susceptible to primary adherence and 18 hour biofilm formation by P. aeruginosa than the PMMA and silicone IOLs, indicating that this material reduced pseudomonad adherence and the risk of endophthalmitis following cataract surgery.

Is it possible to prevent bacterial adhesion onto ureteric stents?

The aim of this study was to determine whether the use of bactericidal coatings or immersion in antibiotic solution reduces or prevents bacterial adhesion onto ureteric stents. Precut segments of full silicone, silver-coated and hydrogel-coated ureteric stents were incubated with two uropathogenic bacterial strains with and without previous immersion in antibiotic solution. Tobramycin, ceftriaxone and ciprofloxacin solutions were used, as these antibiotics are commonly administered for the prophylaxis and treatment of urinary tract infection (UTI). Microbiological analysis showed that immersion of ureteric stents in ceftriaxone and ciprofloxacin yielded a significant reduction of bacterial adhesion, whereas immersion in tobramycin did not. The surface material of the stents had no direct influence on bacterial adhesion. In this experimental study, neither the silver nor the hydrogel coat reduced bacterial adhesion onto ureteric stents whereas immersion in a suitable antibiotic solution significantly reduced and even prevented this phenomenon, probably due to the adhesion of the antibiotic onto the stent surface. Prevention of bacterial adhesion onto ureteric stents is essential to reduce the risk of UTI in connection with these devices.

Bacterial adhesion and biofilm formation on various double-J stents in vivo and in vitro

The aim of this study was to determine whether bacterial adhesion and biofilm formation occur on various ureteric stent materials in vivo and in vitro and whether there is any correlation between biofilm formation and urinary tract infection. Using an open surgical procedure, 23 double-J stents of 8 different types were inserted in the ureters of 13 piglets. After 6 weeks intubation, 2 (9%) of the 23 stented renal units yielded positive urine culture. Scanning Electron Microscopy (SEM) showed sporadic bacteria on 7 (30%) of the 23 indwelling ureteric stents and bacterial biofilms on only 2 (9%), those indwelling the renal units which yielded positive urine cultures. Precut segments of the 8 double-J stent brands were incubated with 5 different bacterial strains. Microbiological and SEM analysis of the stents revealed that only 0.1-0.01% of the bacterial inoculum adhered to the stents. There was no statistically significant difference in bacterial adherence to the various stent materials. Interestingly, the two Escherichia coli strains with P-fimbriae adhered significantly more than the two without P-fimbriae. Sporadic bacterial adhesion to ureteric stents seemed to have little clinical significance whereas biofilm formation seemed to result in urinary tract infection. None of the tested stents proved to be superior to the others in this respect, and adhesion appeared to depend on the virulence of the bacteria rather than the properties of the biomaterials.