The effects of electric current on bacteria colonising intravenous catheters

Microampere Electric Current Causes Bacterial Membrane Damage and Two-Way Leakage in a Short Period of Time

Physical agents, such as low electric voltage and current, have recently gained attention for antimicrobial treatment due to their bactericidal capability. Although microampere electric current was shown to suppress the growth of bacteria, it remains unclear to what extent the microampere current damaged the bacterial membrane. Here, we investigated the membrane damage and two-way leakage caused by microampere electric current (≤100 μA) with a short exposure time (30 min). Based on MitoTracker staining, propidium iodide staining, filtration assays, and quantitative single-molecule localization microscopy, we observed significant membrane damage, which allowed two-way leakage of ions, small molecules, and proteins. This study paves the way to new development of antimicrobial applications for ultralow electric voltage and current.IMPORTANCE Although electric voltage and current have been studied for a long time in terms of their ability to suppress the growth of bacteria and to kill bacteria, increasing interest has been aroused more recently due to the prevalence of antibiotic resistance of microbes in past decades. Toward understanding the antimicrobial mechanism of low electric voltage and current, previous studies showed that treating bacteria with milliampere electric currents (≥5 mA) for ≥72 h led to significant damage of the bacterial membrane, which likely resulted in leakage of cellular contents and influx of toxic substances through the damaged membrane. However, it remains unclear to what extent membrane damage and two-way (i.e., inward and outward) leakage are caused by lower (i.e., microampere) electric current in a shorter time frame. In this work, we set out to answer this question. We observed that the membrane damage was caused by microampere electric current in half an hour, which allowed two-way leakage of ions, small molecules, and proteins.

Electroactive Smart Polymers for Biomedical Applications

The flexibility in polymer properties has allowed the development of a broad range of materials with electroactivity, such as intrinsically conductive conjugated polymers, percolated conductive composites, and ionic conductive hydrogels. These smart electroactive polymers can be designed to respond rationally under an electric stimulus, triggering outstanding properties suitable for biomedical applications. This review presents a general overview of the potential applications of these electroactive smart polymers in the field of tissue engineering and biomaterials. In particular, details about the ability of these electroactive polymers to: (1) stimulate cells in the context of tissue engineering by providing electrical current; (2) mimic muscles by converting electric energy into mechanical energy through an electromechanical response; (3) deliver drugs by changing their internal configuration under an electrical stimulus; and (4) have antimicrobial behavior due to the conduction of electricity, are discussed.

Abnormal Rheological Phenomena in Newtonian Fluids in Electroosmotic Flows in a Nanocapillary

Abnormal rheological phenomena arising in Tris-borate-ethylenediaminetetraacetic acid solutions (believed to be Newtonian fluids) were observed in direct current electroosmotic flows within a nanocapillary with a diameter of 200 nm under a low electric field of tens of volts per meter. In solutions with different concentrations and pH values, the flow behavior indices of the power-law fluids were calculated on the basis of current-voltage relations. When the electric field intensity was below a critical value of 6.7 V/m, the fluids exhibited dilatant (shear thickening) effects. Fluid viscosity changed with electric field intensity because the near-wall shear rate of an electroosmotic flow changes with electric field intensity via a power-law relation. When the electric field intensity surpasses the critical electric field, the fluid again becomes Newtonian and has constant viscosity. The investigation shows that in nanocapillaries, fluids commonly believed to be Newtonian can become non-Newtonian near walls as a result of strong nanoscale interfacial effects. The results can also improve our understanding of electroosmosis-related transport phenomena in nanofluidics and biomedical science.

Demonstration of biofilm removal from type 304 stainless steel using pulsed-waveform electropolishing

This article describes an electrochemical method to remove bacterial biofilm from a stainless steel (SS) surface using a potential pulse/reverse pulse technique. This technique employs a periodic waveform that consists of anodic and cathodic pulses. The pulses can effectively strip a thin layer of metal off the SS surface, along with the adherent biofilm, in a saline solution. Not only can the pulses effectively remove biofilm from the SS surface, but they also regenerate the original mirror-like shiny surface. The importance of this electrochemical biofilm removal method is its wide applicability for any types of biofilms. That is, instead of directly removing the biofilm, it removes a very thin layer of the metal under the biofilm. Thus, the removal process is independent to the nature of the biofilms. Furthermore, this electrochemical biofilm removal method is rapid (less than 30 s of potential pulse time) and does not require hazardous chemicals.

Direct electric current modifies important cellular aspects and ultrastructure features of Candida albicans yeasts: Influence of doses and polarities

Available treatments against human fungal pathogens present high levels of resistance, motivating the development of new antifungal therapies. In this context, the present work aimed to analyze direct electric current (DC) antifungal action, using an in vitro apparatus equipped with platinum electrodes. Candida albicans yeast cells were submitted to three distinct conditions of DC treatment (anodic flow-AF; electroionic flow-EIF; and cathodic flow-CF), as well as different charges, ranging from 0.03 to 2.40 C. Our results indicated C. albicans presented distinct sensibility depending on the DC intensity and polarity applied. Both the colony-forming unit assay and the cytometry flow with propidium iodide indicated a drastic reduction on cellular viability after AF treatment with 0.15 C, while CF- and EIF-treated cells stayed alive when DC doses were increased up to 2.40 C. Additionally, transmission electron microscopy revealed important ultrastructural alterations in AF-treated yeasts, including cell structure disorganization, ruptures in plasmatic membrane, and cytoplasmic rarefaction. This work emphasizes the importance of physical parameters (polarity and doses) in cellular damage, and brings new evidence for using electrotherapy to treat C. albicans pathology process. Bioelectromagnetics. 38:95-108, 2017. © 2016 Wiley Periodicals, Inc.

Electrically conductive catheter inhibits bacterial colonization

PURPOSE

To design, prototype, and assess a custom vascular access catheter for its ability to inhibit bacterial colonization in vitro and to optimize electric parameters for efficacy and safe translation.

MATERIALS AND METHODS

A vascular access catheter with conductive elements was designed and custom fabricated with two electrodes at the tip, separated by a nonconductive segment. The catheter was colonized with Staphylococcus aureus and incubated at predetermined current levels (4-8 µA) and durations (4-24 h). Catheters were compared using bacterial counts and scanning electron microscopy (SEM).

RESULTS

Bacteria colony-forming units were reduced significantly (P < .05) by > 90% (91.7%-100%) in all uninterrupted treatment arms that included electric current (4 µA or 8 µA) of at least 8 hours' duration. Qualitative analysis using SEM revealed that the treated catheter exposed to electric current had markedly less bacteria compared with the untreated catheter.

CONCLUSIONS

This catheter with conductive elements inhibits bacterial colonization in vitro when very small electric current (4-8 µA) is applied across the tip for 8-24 hours. In vivo validation is requisite to future translation to the clinical setting.

1.5 V battery driven reduced graphene oxide-silver nanostructure coated carbon foam (rGO-Ag-CF) for the purification of drinking water

A porous carbon foam (CF) electrode modified with a reduced graphene oxide-Ag (rGO-Ag) nanocomposite has been fabricated to purify water. It can perform as an antibacterial device by killing pathogenic microbes with the aid of a 1.5 V battery, with very little power consumption. The device is recycled ten times with good performance for long term usage. It is shown that the device may be implemented as a fast water purifier to deactivate the pathogens in drinking water.

Effects of low electric current (LEC) treatment on pure bacterial cultures

AIMS

This research focused on the effects of low electric current (LEC) on the cell viability and metabolic activity of Escherichia coli and Bacillus cereus.

METHODS AND RESULTS

Different LEC intensities at fixed amperage were applied, employing either graphite or copper electrode pairs, and the effects were determined by conventional cultural methods and bioindicators. On E. coli, the LEC with graphite electrodes at 5 and 10 mA led to no significant variation, but at 20 and 40 mA there was increasing inhibition of both the enzymatic activities and growth, and a reduction in ATP content. On B. cereus, similar experiments at the lower amperages did not have any inhibitor effects, however, the 40 mA current stimulated growth, ATP content and some enzymatic activities. The LEC treatment using copper electrodes caused, already at 5 mA, inhibition of bacterial growth and metabolic and enzymatic activities in both E. coli and B. cereus.

CONCLUSIONS

On the basis of the obtained results using different amperages and electrodes, we can conclude that E. coli seem to be more sensitive compared with B. cereus.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study increases the knowledge on LEC treatment effects on the pure bacterial cultures.

Prevention of pin tract infection in external stainless steel fixator frames using electric current in a goat model

Pin tract infections of external fixators used in orthopaedic reconstructive bone surgery are serious complications that can eventually lead to periostitis and osteomyelitis. In vitro experiments have demonstrated that bacteria adhering to stainless steel in a biofilm mode of growth detach under the influence of small electric currents, while remaining bacteria become less viable upon current application. Therefore, we have investigated whether a 100microA electric current can prevent signs of clinical infection around percutaneous pins, implanted in the tibia of goats. Three pins were inserted into the lateral right tibia of nine goats, of which one served for additional frame support. Two pins were infected with a Staphylococcus epidermidis strain of which one pin was subjected to electric current, while the other pin was used as control. Pin sites were examined daily. The wound electrical resistance decreased with worsening of the infection from a dry condition to a purulent stage. After 21 days, animals were sacrificed and the pins taken out. Infection developed in 89% of the control pin sites, whereas only 11% of the pin sites in the current group showed infection. These results show that infection of percutaneous pin sites of external fixators in reconstructive bone surgery can be prevented by the application of a small DC electric current.

Central venous access

Central venous access plays an important role in the management of an ever-increasing population of patients ranging from those that are critically ill to patients with difficult clinical access. Interventional radiologists are key in delivering this service and should be familiar with the wide range of techniques and catheters now available to them. A comprehensive description of these catheters with regard to indications, technical aspects of catheterization, success rates, and associated early and late complications, as well as a review of various published guidelines on central venous catheter insertion are given in this article.

Prevention of catheter-related bloodstream infections: An appraisal of developments in designing an infection-resistant 'dream dialysis-catheter' (Review Article)

With the increasing number of elderly, diabetics and debilitated patients being accepted for haemodialysis (HD), the use of central venous catheters (CVCs) as vascular access has become more widespread, with an inevitable inherent risk of catheter-related bloodstream infections (CRBSI) and ensuing mortality. No reliable plans for the effective management of CRBSI without actually sacrificing vascular access sites are presently available. Therefore, the onus really falls on renal physicians to make effective use of the established supportive guiding principles, practices, policies and programs to prevent CRBSI among HD patients. A huge body of research in polymer industry has aimed at alterations of physical, chemical, biological and immunological properties of CVCs to prevent the bacterial colonization of catheters. Developing an infection-resistant dialysis catheter has been an elusive dream. This article analyses the current state-of-the-art strategies aimed at preventing CRBSI and also reviews the progress made to date, in the direction of development of a 'bioactive' thrombosis and infection-resistant dialysis catheter.

Infections associated with medical devices: pathogenesis, management and prophylaxis

The insertion or implantation of foreign bodies has become an indispensable part in almost all fields of medicine. However, medical devices are associated with a definitive risk of bacterial and fungal infections. Foreign body-related infections (FBRIs), particularly catheter-related infections, significantly contribute to the increasing problem of nosocomial infections. While a variety of micro-organisms may be involved as pathogens, staphylococci account for the majority of FBRIs. Their ability to adhere to materials and to promote formation of a biofilm is the most important feature of their pathogenicity. This biofilm on the surface of colonised foreign bodies is regarded as the biological correlative for the clinical experience with FBRI, that is, that the host defence mechanisms often seem to be unable to handle the infection and, in particular, to eliminate the micro-organisms from the infected device. Since antibacterial chemotherapy is also frequently not able to cure these infections despite the use of antibacterials with proven in vitro activity, removal of implanted devices is often inevitable and has been standard clinical practice. However, in specific circumstances, such as infections of implanted medical devices with coagulase-negative staphylococci, a trial of salvage of the device may be justified. All FBRIs should be treated with antibacterials to which the pathogens have been shown to be susceptible. In addition to systemic antibacterial therapy, an intraluminal application of antibacterial agents, referred to as the 'antibiotic-lock' technique, should be considered to circumvent the need for removal, especially in patients with implanted long-term catheters. To reduce the incidence of intravascular catheter-related bloodstream infections, specific guidelines comprising both technological and nontechnological strategies for prevention have been established. Quality assurance, continuing education, choice of the catheter insertion site, hand hygiene and aseptic techniques are aspects of particular interest. Furthermore, all steps in the pathogenesis of biofilm formation may represent targets against which prevention strategies may be directed. Alteration of the foreign body material surface may lead to a change in specific and nonspecific interactions with micro-organisms and, thus, to a reduced microbial adherence. Medical devices made out of a material that would be antiadhesive or at least colonisation resistant would be the most suitable candidates to avoid colonisation and subsequent infection. Another concept for the prevention of FBRIs involves the impregnation of devices with various substances such as antibacterials, antiseptics and/or metals. Finally, further studies are needed to translate the knowledge on the mechanisms of biofilm formation into applicable therapeutic and preventive strategies.

Short-duration low-direct-current electrical field treatment is a practical tool for considerably reducing counts of gram-negative bacteria entrapped in gel beads

Application of a direct-current electrical field for very short times can serve as a practical nonthermal procedure to reduce or modify the microbial distribution in gel beads. The viability of Escherichia coli and Serratia marcescens entrapped in alginate and agarose beads decreases as the field intensity and duration of electrical field increase.

Clinical review: new technologies for prevention of intravascular catheter-related infections

Intravascular catheters have become essential devices for the management of critically and chronically ill patients. However, their use is often associated with serious infectious complications, mostly catheter-related bloodstream infection (CRBSI), resulting in significant morbidity, increased duration of hospitalization, and additional medical costs. The majority of CRBSIs are associated with central venous catheters (CVCs), and the relative risk for CRBSI is significantly greater with CVCs than with peripheral venous catheters. However, most CVC-related infections are preventable, and different measures have been implemented to reduce the risk for CRBSI, including maximal barrier precautions during catheter insertion, catheter site maintenance, and hub handling. The focus of the present review is on new technologies for preventing infections that are directed at CVCs. New preventive strategies that have been shown to be effective in reducing risk for CRBSI, including the use of catheters and dressings impregnated with antiseptics or antibiotics, the use of new hub models, and the use of antibiotic lock solutions, are briefly described.

Evaluation of the silver iontophoretic catheter in an animal model

Silver iontophoretic catheters (SIC) were shown to be highly efficacious in preventing catheter infections in vitro and in a rabbit model (J. Infect. Dis. 173 (1996) 495). Furthermore, we sought to determine the safety and durability of SIC prior to use in humans. A total of 30 New Zealand white rabbits (3-4 kg) were randomly assigned to one of three groups whereby SIC or Arrow Guard (AG) catheters were tunneled and inserted in the jugular vein. All animals were followed for 2-12 weeks after catheter implantation. Blood was collected from each rabbit for assessment of toxicity and determination of silver levels. The electrical current generated by each SIC was measured once daily. At the end of the follow-up period, tissue samples were collected from the skin surrounding the catheter, the lungs, spleen, and liver. Microscopically, none of the tissues examined from any of the animals showed evidence of silver deposits, silver toxicity, thermal or electrical injury. The silver levels in the animals that received the SIC ranged from 0.1 to 2.23 microg/l with a mean of 0.62 (+/-0.44 SD). In conclusion SIC were safe with normal serum silver levels and were not associated with any local or systemic toxicity.

Effects of low electric treatment on yeast microflora

AIMS

To contribute to the understanding of phenomena related to different intensity electric current treatments on the growth and metabolism of selected micro-organisms using laboratory samples of pure and co-cultures (Saccharomyces cerevisiae strain 404 and Hanseniaspora guilliermondii strain 465).

METHODS AND RESULTS

Low electric current (10, 30, 50 and 100 mA) was applied to prepared samples. Parameters, such as polarity, treatment duration (18-48 h) and type of inoculum yeast, were varied one at a time to highlight their cause-effect relationships. The effects on cell activity as well as microflora viability were assessed. Bioindicators capable of describing the phenomena caused by the electric current on the microflora were identified.

CONCLUSIONS

Results demonstrated that a low voltage treatment using graphite electrodes had a greater effect on the viable S. cerevisiae strain 404 microflora. There was less bactericidal activity in the S. cerevisiae strain 404 than in the H. guilliermondii strain 465.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results may be of significant importance in the development of new technological processes in the fields of agriculture and food, particularly new fermenting process controls.

Central line infections

Central venous catheters are commonly used in the critical care setting. Unfortunately, their use is often associated with complications, including fatal infections. Making the diagnosis of central venous catheter infection can be difficult. Additionally, resistance among the more common organisms that cause catheter-related infection is increasing. However, our understanding of the pathogenesis of catheter infection is improving through examination of biofilms. Also, our ability to diagnose catheter-related infections more accurately is improving with new techniques. There is new hope for ruling out catheter-related infection before removal by several methods, including a rapid enzyme-linked immunosorbent assay and the use of time differential for microbial growth between blood cultures obtained from a peripheral site and the catheter itself. Prevention through the use of barrier techniques and antimicrobial-coated catheters has been demonstrated to be of value in reducing catheter-related infection with these devices.

The promise of novel technology for the prevention of intravascular device-related bloodstream infection. I. Pathogenesis and short-term devices

Intravascular devices (IVDs) are widely used for vascular access but are associated with substantial risk of development of IVD-related bloodstream infection (BSI). The development of novel technologies, which are based on an understanding of pathogenesis, promises a quantum reduction in IVD-related infections in an era of growing nursing shortages. Infections of short-term IVDs (that is, those in place <10 days), including peripheral venous catheters, noncuffed and nontunneled central venous catheters (CVCs), and arterial catheters, derive mainly from microorganisms colonizing the skin around the insertion site, which most often gain access extraluminally. More-effective cutaneous antiseptics, such as chlorhexidine, a chlorhexidine-impregnated sponge dressing, CVCs with an anti-infective coating, anti-infective CVC hubs, and novel needleless connectors, have all been shown to reduce the risk of IVD-related BSI in prospective randomized trials. The challenge for the future will be to identify new preventative technologies and to begin to adapt more widely those technologies already shown to be efficacious and cost-effective.

Pathogenesis of catheter-related infections: lessons for new designs

In the last decade, two main strategies have been employed in the prevention of catheter-related infections: the creation of anti-adhesive biomaterials using physicochemical methods, and the incorporation of antimicrobial or antiseptic agents into current polymer biomaterials. There has been limited success with the first approach. Intravascular catheters and cuffs with an antimicrobial coating have been developed in recent years. Nevertheless, preventive strategies should avoid the use of therapeutic antibiotics. Exposure to antimicrobial agents could favor the development of resistance or the expression of genes responsible for biofilm formation. The use of these catheters should be restricted to situations where the rate of infection is high despite adherence to other strategies that do not incorporate antimicrobial agents. Better knowledge of the pathogenesis of catheter-related infections will facilitate the design of new devices that avoid the use of antimicrobial agents and decrease the risk of associated bloodstream infections. This could include the use of 'biospecific polymers' coated with anti-adhesive molecules or the use of agents which might block the expression of genes controlling biofilm formation for the most prevalent pathogens.

Efficacy of antiadhesive, antibiotic and antiseptic coatings in preventing catheter-related infections: review

In recent years, central venous catheters (CVCs) are increasingly used in clinical practice. However, complications such as local or systemic infections are frequent for both temporary and indwelling vascular catheters. Annually, in the United States of America there are more than 200,000 cases of nosocomial bloodstream infections (BSIs), of which 90% are related to the use of an intravascular device. These infections are associated with increased morbidity and mortality, prolonged hospitalization and growing medical costs. Technological treatments of polymer surfaces including coating the catheter with antimicrobial substances may be promising tools for prevention of catheter-associated infections. A large number of surface-treated central venous catheters are now commercially available. In this paper the features and the clinical efficacy of different antimicrobial coatings are reviewed.

Lack of effect of an externally applied electric field on bacterial adhesion to glass

Deposition to glass of Streptococcus salivarius HB-C12 and Staphylococcus epidermidis 3399 in a parallel plate flow chamber in the absence and presence of an externally applied electric field has been studied experimentally. No effect on bacterial adhesion, including initial deposition rates, numbers of adhering bacteria after 4 h, spatial distributions of adhering bacteria and air bubble induced detachment, was found. A theoretical analysis shows that electric fields applied over a 150 µm thin glass substratum do not have a sufficiently strong effect on its surface potential to influence bacterial adhesion.

Novel methods for the prevention of infection of intravascular devices

Infections are often caused by bacteria that gain access either from the skin during insertion, or by migration from the skin to the surrounding subcutaneous tissue, once in situ. It is necessary to understand the pathogenesis with regard to sessile or planktonic forms of microorganisms and why they adhere to catheter surfaces, and the interactions between host, catheter and bug. To prevent colonization two general approaches have been adopted: the first concerns the site of insertion-prophylactic antibiotics, tunnelling, intraluminal antibiotic locks, topical application of antibiotics or antiseptics, cutaneous disinfection pre- and post-insertion with various antiseptics, catheter site care and frequency of dressing changes. The second approach considers the physical nature of catheter material-silver impregnated subcutaneous collagen cuffs, antiseptic hubs, antimicrobial coating of catheters with antibiotics e.g., rifampicin and minocycline, silver ions, chlorhexidine, chlorhexidine and silver sulphadiazine. Only by understanding the pathogenesis of catheter devices whereby micro-organisms are embedded in biofilms and are resistant to the action of antibiotics, will effective preventative measures be possible. In addition a proper risk-management review will be necessary to determine the cost-benefit of such modified catheters.

Hydrogen peroxide for prevention of bacterial growth on polymer biomaterials

BACKGROUND

Despite widespread use of potent antibiotics, infections of artificial implants and catheters are of increasing concern. We tested whether local treatment with 3% hydrogen peroxide (H2O2), long known as an inexpensive wound disinfectant, could prevent or reduce bacterial growth on polymer biomaterials.

METHODS

Two-centimeter-long pieces of polyurethane and silicone tubing were contaminated with a standardized solution of Staphylococcus epidermidis (10(5)/mL) and then rinsed and wiped with saline (0.9%) solution. Bacterial growth was assessed after incubation at 37 degrees C for 24 hours. Bacterial colonies were compared for the following treatments: wiping only with saline; wiping with 1.5%, 2%, or 3% H2O2; pretreating biomaterials with 3% H2O2 and subsequent contamination for 2 and 4 hours without treatment after contamination; and contamination of tubings 1 month after pretreatment with 3% H2O2. The effect of 3% H2O2 was also assessed on contamination with Escherichia coli.

RESULTS

Bacterial growth was reduced by more than 99% when the contaminated tubes were treated with 3% H2O2 compared with saline control (p < 0.001). Lower concentrations of H2O2 were less effective. The length of the contamination period had no influence on the effectiveness of H2O2 when used on polyurethane but did with silicone tubings. Pretreatment with H2O2 1 month before contamination still reduced bacterial growth rate by 90% on polyurethane and by 75% on silicone tubings. Comparable effects on bacterial growth rate were observed for staphylococci (-90%, p < 0.001) and escherichiae (-90%, p < 0.001).

CONCLUSIONS

Local treatment with 3% H2O2 significantly reduced bacterial growth on polymer biomaterials even for 1 month after treatment. This finding might influence clinical strategies of prevention of foreign body infection.

Prevention of central venous catheter-related infection

Infections associated with central venous catheters continue to be a major source of sepsis, particularly in hospitalized patients. In developing a strategy for the prevention of these infections, the source and route of invasion of the causative micro-organisms need to be considered. The main source of micro-organisms is the patient's skin. They can gain access to a catheter at the time of insertion, as well as via the external or internal catheter surfaces. Attempts to reduce the incidence of infections range from the type of skin preparation selected, to care of the insertion site post-catheterization. Improvements in catheter design have also reduced the likelihood of infection and include the development of non-leachable smooth catheters with anti-adhesive coatings. More recently, catheters containing antimicrobial agents have become available and preliminary studies have demonstrated a reduction in microbial colonization and associated sepsis. Future preventative strategies may include the application of low voltage electric current in combination with antimicrobials.

Activity of silver ions in different media

A major problem in medicine is the large number of infections associated with implanted and indwelling devices. Silver coating of medical devices is believed to preserve infection resistance. Several in vitro and animal studies as well as clinical observations on silver-nylon, silver-intramedullary pins, silver-oxide-Foley catheters and silver-coated vascular protheses have been interpreted as successful for the prophylaxis of foreign-body infections. Nevertheless, these products have not been established in clinical use. In this study we have been able to present physico-chemical and pharmacological data as well as simple microbiological experiments explaining the reduced anti-microbial activity of silver-ions in some biological fluids.

Use of pulsed field gel electrophoresis to determine the source of microbial contamination of central venous catheters

Microorganisms detected in situ on the distal tip of central venous catheters (CVC) within 90 min of insertion were investigated using pulsed-field gel electrophoresis to analyse genomic fragments obtained with the SmaI restriction enzyme. Thirty patients received a triple lumen CVC, which was inserted directly through the skin using the Seldinger technique. In a further 30 patients a triple lumen CVC was inserted through a Swan sheath, thereby avoiding direct contact of the CVC with the skin. Staphylococci were isolated from the distal tips of the catheters in 6 patients (5 who had the CVC inserted directly through the skin and 1 who had the CVC inserted via a Swan sheath.) Twenty-three staphylococcal isolates were also isolated from the insertion equipment and the skin swabs surrounding the insertion site of these six patients. All the isolates were genotyped. In one of the patients the organisms isolated from the skin were identical to those on the CVC tip. In two further patients similar organisms were isolated from the insertion equipment and the patients' skin. These results, in addition to the reduced colonisation rates observed when catheters were introduced through a Swan sheath, support the hypothesis that microorganisms from the skin are impacted onto the CVC tip and the CVC insertion equipment at catheter insertion.