Prevention of infections caused by central venous catheters--established and novel measures

Antimicrobial, mechanical and thermal studies of silver particle-loaded polyurethane

Silver-particle-incorporated polyurethane films were evaluated for antimicrobial activity towards two different bacteria: Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Distributed silver particles sourced from silver nitrate, silver lactate and preformed silver nanoparticles were mixed with polyurethane (PU) and variously characterized by field emission scanning electron microscopy (FESEM), fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD) and contact angle measurement. Antibacterial activity against E.coli was confirmed for films loaded with 10% (w/w) AgNO3, 1% and 10% (w/w) Ag lactate and preformed Ag nanoparticles. All were active against S. aureus, but Ag nanoparticles loaded with PU had a minor effect. The apparent antibacterial performance of Ag lactate-loaded PU is better than other Ag ion-loaded films, revealed from the zone of inhibition study. The better performance of silver lactate-loaded PU was the likely result of a porous PU structure. FESEM and FTIR indicated direct interaction of silver with the PU backbone, and XRD patterns confirmed that face-centred cubic-type silver, representative of Ag metal, was present. Young's modulus, tensile strength and the hardness of silver containing PU films were not adversely affected and possibly marginally increased with silver incorporation. Dynamic mechanical analysis (DMA) indicated greater thermal stability.

Central venous catheter infections and antibiotic therapy during long-term home parenteral nutrition: an 11-year follow-up study

BACKGROUND

Catheter-related bloodstream infections are a serious and common complication in patients receiving home parenteral nutrition (HPN).

METHODS

Prevalence of infections, type of agents, and effectiveness of antibiotic therapy were evaluated in 296 patients (133 males, 163 females; mean age 58.2 +/- 13.5 years) receiving HPN for at least 3 months, from January 1995 to December 2006. Patients underwent 99,969 (331 +/- 552; minimum 91, maximum 4353) days of catheterization, corresponding to 93,236 (311 +/- 489; minimum 52, maximum 4353) days of HPN.

RESULTS

Fifty-two patients (24 males and 28 females; 35 oncological and 17 nononcological) were diagnosed with 169 infections. The overall corresponding infection rate was 2.0 per 1000 days of catheterization, with a progressive, regular decrease with time. In 30 cases, immediate central venous catheter removal was necessary. Infections were eradicated in 103 of 139 (74%) cases. As to the most common causative agent, 86 (51%) infections were due to Staphylococcus epidermidis. Of these, 64 were treated from 1995 to 2004, 57 of them (89%) successfully; 22 were treated from 2005 onward, only 7 of them (32%) successfully.

CONCLUSIONS

Although the global infection rate has progressively decreased over the years, S epidermidis has shown an alarming increase in resistance to antibiotic treatment in the last 2 years, suggesting the need for strategies to prevent central venous catheter infection.

Use of catheters with the AgION antimicrobial system in kidney transplant recipients to reduce infection risk

Microbial blood infection represents a high risk for immuno-suppressed patients. Of all catheter-related infections in the bloodstream, 90% result from the use of central venous catheters, the main cause being microbial colonization at the catheter's insertion point or the catheter hub. Between January 2003 and December 2004, 102 patients received a renal transplant including 57 who received a triple-lumen central venous catheter (CVC) during the procedure. Two catheters were used: a standard polyurethane catheter placed in the jugular veina or the subclavian veina for group I, and polyurethane catheters with the AgION antimicrobial system always placed in the subclavian veina for group II. Care and maintenance of the CVCs was standardized in both groups. After catheter removal, the tips were analyzed microbiologically. Of 57 (43.9%) CVCs, 25 were found to be contaminated. In the first group 24 out of 41 CVCs (58.5%) showed bacterial growth, whereas in group II only one catheter (6.6%) had a biofilm. The most common contaminant (18 out of 25, 72%) was Staphylococcus epidermidis. In group II, two patients had positive blood cultures yet a microbiologically sterile CVC. None of the catheters with the AgION antimicrobial system had to be removed owing to local infection or intolerance. The continuous release of silver ions increases the protection against bacteria and fungi during the entire time of catheterization. Use of catheters with the AgION antimicrobial system lead to a marked reduction in catheter-associated infections of the bloodstream.

A prospective, randomized trial of rifampicin-minocycline-coated and silver-platinum-carbon-impregnated central venous catheters*

OBJECTIVE

Central venous catheters are the predominant cause of nosocomial bacteremia; however, the effectiveness of different antimicrobial central venous catheters remains uncertain. We compared the infection rate of silver-platinum-carbon (SPC)-impregnated catheters with rifampicin-minocycline (RM)-coated catheters.

DESIGN

A large, single-center, prospective randomized study.

SETTING

Twenty-two-bed adult general intensive care unit in a large tertiary metropolitan hospital in Brisbane, Australia (2000-2001).

PATIENTS

Consecutive series of all central venous catheterizations in intensive care unit patients.

INTERVENTIONS

Randomization, concealment, and blinding were carefully performed. Catheter insertion and care were performed according to published guidelines. Blood cultures were taken at central venous catheter removal, and catheter-tip cultures were performed by both roll-plate and sonication techniques. Pulsed field gel electrophoresis was used to establish shared clonal origin for matched isolates.

MEASUREMENTS AND MAIN RESULTS

Central venous catheter colonization and catheter-related bloodstream infection were determined with a blinded technique using the evaluation of the extensive microbiological and clinical data collected and a rigorous classification system. Six hundred forty-six central venous catheters (RM 319, SPC 327) were inserted, and 574 (89%) were microbiologically evaluable. Colonization rates were lower for the RM catheters than SPC catheters (25 of 280, 8.9%; 43 of 294, 14.6%; p=.039). A Kaplan-Meier analysis that included catheter time in situ did not quite achieve statistical significance (p=.055). Catheter-related bloodstream infection was infrequent for both catheter-types (RM 4, 1.4%; SPC 5, 1.7%).

CONCLUSIONS

The SPC catheter is a clinically effective antimicrobial catheter; however, the RM catheter had a lower colonization rate. Both catheter types had low rates of catheter-related bloodstream infection. These results indicate that future studies will require similar rigorous methodology and thousands of central venous catheters to demonstrate differences in catheter-related bloodstream infection rates.

A needleless closed system device (CLAVE) protects from intravascular catheter tip and hub colonization: a prospective randomized study

Hub colonization and subsequent intraluminal progression due to frequent opening and manipulation of intravenous systems is the cause of many catheter-related infections (CRI). A prospective, comparative, randomized study was performed to assess a new closed-needleless hub device (CLAVE) compared with conventional open systems (COS). End-points were hub and skin colonization, catheter tip colonization, catheter-related bloodstream infection (CRBSI) and number of accidental needlesticks. All cultures were processed following standard semiquantitative microbiological techniques. The study involved patients who underwent heart surgery over an 11-month period in a post-surgical ICU. During the study period, 352 patients underwent major heart surgery and 1774 catheters were inserted. Overall, 865 catheters in 178 patients were allocated to the CLAVE system and 909 catheters in 174 patients to COS. The groups were similar regarding underlying conditions and risk factors for infection. Comparison of endpoint results in CLAVE and COS groups was as follows: incidence density per 1000 catheter-days of tip colonization: 59.2 versus 83.6 (P=0.003); of hub colonization: 7.56 versus 24.66 (P=0.0017); of skin colonization: 41.5 versus 58.9 (P=0.038); and of CRBSI 3.78 versus 5.89 (P=0.4). There was one accidental needlestick and one catheter-related prosthetic endocarditis in the COS group. Multivariate analysis showed that CLAVE use was an independent protective factor for tip colonization. CLAVE offered significant protection from catheter-tip and hub colonization.

Infective endocarditis in dialysis patients: new challenges and old

BACKGROUND

Since the 1960s chronic hemodialysis (HD) has been recognized as a risk factor for the development of infective endocarditis (IE). Historically, it has been particularly associated with vascular access via dual lumen catheters. We wished to examine the risk factors for, and consequences of, IE in the modern dialysis era.

METHODS

Cases of IE (using the Duke criteria) at St. Thomas' Hospital (1980 to 1995), Guy's (1995 to 2002), and King's College Hospitals (1996 to 2002) were reviewed.

RESULTS

Twenty-eight patients were identified as having developed IE (30 episodes of IE). Twenty-seven patients were on long-term HD and one patient was on peritoneal dialysis (PD). Mean age was 54.1 years, and mean duration of HD prior to IE was 46.3 months. Eight patients were diabetic. Primary HD hemoaccess was an arteriovenous fistula (AVF) in 41.3%, a dual-lumen tunneled catheter (DLTC) in 37.9%, a polytetrafluoroethylene (PTFE) graft in 10.3%, and a dual- lumen non-tunneled catheter (DLNTC) in 4%. The presumed source of sepsis was directly related to hemoaccess in 25 HD patients: DLTC in 48%; AVF in 32%; PTFE in 12%; and DLNTC in 4%. Staphylococcus aureus[including methicillin resistant Staphylococcus aureus (MRSA)] was present in 63.3%. The mitral valve was affected in 41.4% of patients, aortic valve in 37.9% of patients, and both valves were affected in 17.2% of patients. Of note, 51.7% of patients had an abnormal valve before the episode of IE. In 15 cases surgery was undertaken. Fourteen patients survived to discharge, and 12 survived for 30 days. In 15 cases antibiotic treatment alone was employed; in this case, eight patients died and seven survived to discharge.

CONCLUSION

This is the largest reported confirmed IE series in dialysis patients. Infective endocarditis in HD patients remains a challenging problem-although hemoaccess via dual-lumen catheters remains a significant risk, many cases developed in patients with AVFs and this group suffered the greatest mortality. An abnormal valve (frequently calcified) was another risk factor; because valve calcification is now common after 5 years on dialysis, more effort in preventing this avoidable form of ectopic calcification may reduce the risk of developing IE.

Infectious complications of venous access devices

Infection represents one of the most common venous access device (VAD)-related complications requiring catheter removal. Recognition of such complications is essential to provide appropriate therapy in the setting of active infection. This article reviews the definition of various types of infections, as well as reviewing the diagnosis, prevention, and treatment of VAD-related infections.

Prevention and treatment of implanted central venous catheter (CVC) - related sepsis: a report after six years of home parenteral nutrition (HPN)

Catheter-related sepsis is a serious and common complication in patients receiving home parenteral nutrition (HPN). Prevention measures, prevalence of infections, types of agents and implanted central venous catheters (CVC), effectiveness of antibiotic therapy have been evaluated in 221 patients consecutively followed in our unit from January 1995 to December 2000. The clinical diagnosis of catheter-related infection was made using well-defined criteria. Patients were divided into two groups: A and B, receiving instructions with different modalities: standard (A) and detailed (B), respectively. Sixty CVC-related sepsis occurred in 32 (14%) patients. A multivariate analysis showed that the duration of HPN (P<0.001; OR=0.9), type of catheter (P=0.009; OR=0.12) and type of disease (P=0.033; OR=4.92) significantly influence catheter infection. The type of implanted CVC (159 port-a-cath in 153 patients and 71 tunnelled in 68) seems to affect the infection rate, this being lower in tunnelled (P=0.03). Infection rate was lower in B vs A group (P<0.001) with all types of catheters, suggesting the preventive role of very careful training. In particular, the incidence of CVC-related sepsis was 6/1000 days of HPN (i.e. 6/1000 days of catheterization) in Group A and 3/1000 in Group B. Systemic and antibiotic lock therapy was performed with an 83% successful rate. Gram-positive bacteria were the most frequent CVC infection agents, which are usually eradicated by antibiotic therapy lasting 7 days.

Bacterial biofilms and human disease

The term biofilm is used to denote a polymer-encased community of microbes which accumulates at a surface. Biofilms are responsible for a number of diseases of man and, because of the intrinsic resistance of these structures to antibiotics and host defence systems, such diseases are very difficult to treat effectively. The application of new microscopic and molecular techniques to biofilms has revolutionised our understanding of their structure, composition, organisation and activities. This review will describe the role that biofilms play in human disease and will outline our new millennial view of these complex and fascinating bacterial communities.

Tunneled hemodialysis catheter survival: comparison of radiologic and surgical implantation

Cuffed, tunneled hemodialysis catheters (caths) are often implanted in the operating rooms (OR) by surgeons or by interventional radiologists in radiology suites (RS). Comparative outcome studies between OR and RS placed caths are few and tend to favor the specialty of the authors. In this longitudinal study, we monitored cath survival in patients while awaiting maturation of their fistulae, and compared outcomes between OR and RS placement. A total of 95 caths were placed in 50 patients between July 1996 and July 1999. Radiologically placed caths had a shorter primary patency duration than OR placed caths (80 +/- 40 days vs. 100 +/- 31 days, p = 0.04) and a lower primary patency rate at 120 days than OR placed caths (42% vs. 67%, p = 0.04). Cumulative infection rate per 1,000 catheter days was higher in RS than OR cases (3.8 Vs 2.2, p = 0.09), whereas mean sepsis free duration was shorter in RS than OR (60 +/- 45 days vs. 88 +/- 40 days, p = 0.02). The risk of infection was 1.7 times greater in RS than OR cases (chi-square = 6.4, p = 0.01). The RS placed caths also had a higher rate of primary nonfunction (31% vs. 8.3%, p = 0.04) and bleeding complications (42% vs. 17%, p = 0.04), but significantly shorter procedure scheduling time than OR cases (1.1 +/- 0.3 days vs. 2.5 +/- 0.6 days, p < 0.0001). In conclusion, radiologically placed caths seem to have higher rates of infection, bleeding, and functional failure but shorter scheduling time than surgically placed caths. Discussions are under way to improve the survival of RS placed caths at our affiliated hospitals.

Toward new biomaterials

Polymers are widely used for a large range of medical devices used as biomaterials on a temporary, intermittent, and long-term basis. It is now well accepted that the initial rapid adsorption of proteins to polymeric surfaces affects the performance of these biomaterials. However, protein adsorption to a polymer surface can be modulated by an appropriate design of the interface. Extensive study has shown that these interactions can be minimized by coating with a highly hydrated layer (hydrogel), by grafting on the surface different biomolecules, or by creating domains with chemical functions (charges, hydrophilic groups). Our laboratory has investigated the latter approach over the past 2 decades, in particular the synthesis and the biological activities of polymers to improve the biocompatibility of blood-contacting devices. These soluble and insoluble polymers were obtained by chemical substitution of macromolecular chains with suitable groups able to develop specific interactions with biological components. Applied to compatibility with the blood and the immune systems, this concept has been extended to interactions of polymeric biomaterials with eukaryotic and prokaryotic cells. The design of new biomaterials with low bacterial attachment is thus under intensive study. After a brief overview of current trends in the surface modifications of biocompatible materials, we will describe how biospecific polymers can be obtained and review our recent results on the inhibition of bacterial adhesion using one type of functionalized polymer obtained by random substitution. This strategy, applied to existing or new materials, seems promising for the limitation of biomaterial-associated infections.

A new technology of microdispersed silver in polyurethane induces antimicrobial activity in central venous catheters

Metal ions or metal ions in complexes or compounds have been used for centuries to disinfect fluids, solids and tissues. The biocidal effect of silver, with its broad spectrum of activity including bacterial, fungal and viral agents, is particularly well known and the term "oligodynamic activity" was coined for this phenomenon. Silver ions have an affinity to sulfhydryl groups in enzyme systems of the cell wall, through which they interfere with the transmembranous energy transfer and electron transport of bacterial microorganisms. Silver ions also block the respiratory chain of microorganisms reversibly in low concentrations and irreversibly in higher concentrations. Binding to the DNA of bacteria and fungi increases the stability of the bacterial double helix and thus inhibits proliferation. There is no cross resistance with antibiotics and also no induction of antimicrobial resistance by silver ions. The concentrations required for bactericidal activity are in the range 10(-9) mol/l. These concentrations can be achieved in solution by the interaction of metallic silver with electrolytes only if there is a large enough surface of silver. By a novel technology, metallic silver is distributed in submicron particles in polyurethane and results in a concentration of 0.8% in an active surface of 450 cm2/g polyurethane. Polyurethane is hygroscopic and rapidly attracts water; the interaction of electrolyte solutions with the extremely finely distributed silver throughout the polyurethane releases bactericidal concentrations of silver ions over a period of years to the surface of the material. The electronegatively charged surface of bacteria attracts the positively charged silver ions. The concentrations released from the polyurethane are far below the toxic concentrations for humans.

Reduced rates of catheter-associated infection by use of a new silver-impregnated central venous catheter

A central venous catheter with a new form of silver impregnation of the internal and external surfaces was investigated for antimicrobial activity and tolerance in patients in a controlled comparative, prospective and randomized clinical study. Commercially available catheters with no antimicrobial activity were used as controls. One hundred sixty-five catheters were included in the final evaluation. All catheters were percutaneously inserted for the first time with a duration of > or = 5 days and a microbiological examination of the catheter tip. Catheter location (> 90% internal jugular vein), mean duration of catheterization (8-9 days), patients' age and diagnosis were comparable in both groups. Silver-impregnated catheter tips showed an incidence of colonization in 14.2/1000 catheter days and control catheters in 22.8/1000 catheter days. This represents a reduction of 37.7%. Catheter-associated infections were diagnosed in the silver group in 5.26/1000 catheter days and 18.34/1000 catheter days in the control group, indicating a reduction rate of 71.3% (P < 0.05, chi 2-test). No complications or side effects were documented in either group.