Contamination of central venous catheters in immunocompromised patients: a comparison between two different types of central venous catheters

Catheters impregnated with silver have been proposed as a means of reducing catheter-related infection. We therefore performed a prospective randomized study to compare a new silver-impregnated central venous catheter (CVC) with a commercially available CVC in a cohort of immunocompromised patients. We studied 157 patients of whom 97 could be analysed. The median indwelling time in the study group (SC) was 10.5 days and 11 days in the control group (CC). The incidence of contamination in the SC group was 15.6 vs 24.6 in the CC group referring to 1000 catheter days. In both groups, we found 6% of catheter-related infections according to the definitions of a published scoring system. The differences between the two groups were not significant. We conclude that the SC decrease the incidence of catheter contamination and may have a positive effect on the reduction of CVC-related infections.

Immunogenicity and reactogenicity of a single dose of a diphtheria--tetanus--acellular pertussis component vaccine (DTaP) compared to a diphtheria--tetanus toxoid (Td) and a diphtheria toxoid vaccine (d) in adults

We compared immunogenicity and reactogenicity of a single dose of DTaP vaccine (containing tetanus and diphtheria toxoids and four acellular pertussis antigens) with conventional Td- or d-vaccines in 180 German adults. Antibody values against diphtheria and tetanus toxin and against the pertussis antigens fimbriae (FIM), filamentous hemagglutinin (FHA) and pertussis toxin (PT) were measured in pre- and post-immunization sera. Reactogenicity was determined by a patient diary card. Pre-immunization antibody values against diphtheria toxin were low in all three vaccine groups. After immunization, > or = 80% of the vaccinees in all three groups were fully protected (> or = 0.1 IU/ml), but geometric mean values were significantly higher in DTaP recipients compared to Td or d recipients (1.65 vs. 0.44 and 0.48, respectively; both P < 0.05). Pre-immunization antibody values against tetanus toxin were high in all three groups, and after immunization 100% of the vaccinees were protected (> or = 0.1 IU/ml). Furthermore, substantial antibody responses against pertussis antigens were elicited in DTaP recipients with geometric mean rises of 22.5, 4.1 and 7.5 for antibodies against FHA, fimbriae and PT, respectively. All three vaccines were well tolerated. Frequency and severity of local reactions were similar between DTaP and Td recipients and even less common in d recipients. Since DTaP did provide a significant boost of anti-pertussis antibodies and a significantly higher anti-diphtheria response than conventional Td vaccine without an increase of side effects, it might be an appropriate candidate for use in adults.

Comparison of immunogenicity and reactogenicity of a measles, mumps and rubella (MMR) vaccine in German children vaccinated at 9-11, 12-14 or 15-17 months of age

Children aged 9-11, 12-14 or 15-17 months, respectively were vaccinated with a measles, mumps and rubella (MMR) vaccine and serum antibody responses and reactogenicity were compared. The data of 118 children could be analysed (group 1=9-11 months, n=46; group 2=12-14 months, n=29, group 3, 15-17 months, n=43). The only significant difference observed was for seroconversion against measles virus between group 1 and group 3 (84.8% vs 100%, p=0.012). No serious adverse events were reported. Local side reactions were mild, infrequent and independent of age. Immunisation against MMR is safe and effective even when administered before the currently recommended age of 12 months.

Optimal tobramycin dosage in patients with cystic fibrosis--evidence for predictability based on previous drug monitoring

A retrospective analysis of files of patients with cystic fibrosis and pulmonary exacerbations was performed to investigate whether an individual dosage of tobramycin once established by serum level determination allows a reliable prediction of the adequate dosage in a consecutive exacerbation. All patients hospitalized > or = 2 times between May 1997 and September 1998 with pulmonary exacerbation due to Pseudomonas aeruginosa infection susceptible to tobramycin were included. The initial dosage to tobramycin was 5 mg/kg body weight every 12 h followed by drug level determinations to establish the optimal dose. In a consecutive exacerbation the same dosage per kg body weight was used again and drug level determinations were repeated. Sixteen patients (six female = 38%) with a mean age of 24 years (median: 26 years, range: 9-33) were hospitalized for 49 pulmonary exacerbations (2-6 per patient, mean: 3, median: 2.5). During the first episode of tobramycin treatment in the study period all trough levels were < 2 microg/ml (median: 0.6) and the peak levels were 7.1-16.9 microg/ml (median: 11.9). In four patients the peak level was > 12 microg/ml. In 28 consecutive episodes the dosage of tobra myci n was chosen based on optimal results of previous drug level monitoring and in 27 instances (96%) the previously established optimal dose was confirmed. In five consecutive episodes the tobramycin dosage had been increased erroneously and this resulted in abnormally high peak levels in three cases. These findings suggest that a safe and therapeutic tobramycin dosage in an individual patient with cystic fibrosis is predictable based on a previously established optimal dosage.

Analysis of the acute cytotoxicity of the Erlanger silver catheter

The Erlanger silver catheter consists of a new form of polyurethane, which contains finely dispersed metallic silver. The aim of this study was to establish the biocompatibility of this intravenous catheter by investigating the acute cytotoxicity of extracts from the Erlanger silver catheter on human fibroblasts and lymphocytes. Extracts of the Erlanger silver catheter were not cytotoxic for MRC-5 human fibroblasts nor for sensitized phytohemagglutinin (PHA)-stimulated human lymphocytes. The addition of silver powder of up to 2% by weight to the basic catheter polyurethane Tecothane led to no increase in acute cytotoxicity in comparison with untreated Tecothane. The Erlanger silver catheter is a new intravenous catheter with good biocompatibility.

A new scoring system for the clinical diagnosis of catheter-related infections

It is difficult to make the clinical diagnosis of catheter-related infections using the available and established definitions of the HICPAC (Hospital Infection Control Practices Advisory Committee) of the CDC (Centers for Disease Control, definitions of nosocomial infections). The scoring system shown here is a modification of these definitions and has enabled the causal relationship between the catheter and clinical episodes of systemic infections to be quantitatively graded. The scoring system included the following criteria: height and rate of rise of body temperature, attendant shivering, identification of pathogens in blood and/or catheter tip cultures, improvement in the clinical course after catheter removal, signs of catheter exit site inflammation and results of diagnostic tests for other possible sources of infection. These criteria were graded using points and weighted according to their specificity. The comparative evaluation of 65 episodes of systemic infections using the scoring system and the diagnostic criteria of HICPAC showed agreement in 85%. No case was graded "false-negative." In nine of ten false-positive cases additional findings supported the presence of a catheter-associated infection. This scoring system appears, therefore, to be more sensitive than existing diagnostic criteria, without loss of specificity.

The Erlanger silver catheter: in vitro results for antimicrobial activity

The antimicrobial activity of a silver-impregnated polymer catheter (the Erlanger silver catheter) was demonstrated by determining the microbial adhesion to the surface of the catheter and by measuring the rate of proliferation (viability) of microorganisms at this site. On the surface of a catheter impregnated with silver, according to previously described methods, the bacterial adhesion of Staphylococcus epidermidis is reduced by 28-40%. Bacterial proliferation on the surface of the catheter and biofilm production are also substantially reduced by the elution of free silver ions from the catheter matrix. Bacteriostatic and bactericidal activities can be determined. The antimicrobial efficacy of the silver catheter is not reduced by blood components. There is no loss in antimicrobial activity for weeks after preincubation in water or phosphate buffered saline. The antimicrobial activity depends on the extent of the active silver surface.

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.

Thrombogenicity testing of central venous catheters in vitro

To date there have been no standard methods for assessing the thrombogenicity of central venous catheters. A procedure for testing the thrombogenicity of intravenous lines such as the silver-impregnated catheter by continuous blood flow in vitro was therefore developed. For this test, fresh blood was drawn from healthy human donors and anti-coagulated with sodium citrate (1:9). All material tested (catheter tubes with and without silver manufactured in the same way, polyethylene tubes and tubes with potentially thrombogenic material) were perfused through their lumen with anticoagulated blood for up to 31 hours. Blood samples were collected at different times from the test system at sites before and after the perfusion of the test catheters. The hemoglobin concentration, erythrocyte, leukocyte and thrombocyte counts and markers for thrombin activation (thrombin-antithrombin III-complex, F1 + 2)-prothrombin fragments) and for hyperfibrinolysis (d-dimers) were determined. No thrombin activation or signs of hyperfibrinolysis were detected in any material tested. Polyethylene tubes were found to cause hemolysis, as shown by a decrease in hemoglobin content from 15 g% to 4.5 g%. Tecothane tubes with and without silver did not induce hemolysis.

Clinical study of the Erlanger silver catheter--data management and biometry

The clinical evaluation of venous catheters for catheter-induced infections must conform to a strict biometric methodology. The statistical planning of the study (target population, design, degree of blinding), data management (database design, definition of variables, coding), quality assurance (data inspection at several levels) and the biometric evaluation of the Erlanger silver catheter project are described. The three-step data flow included: 1) primary data from the hospital, 2) relational database, 3) files accessible for statistical evaluation. Two different statistical models were compared: analyzing the first catheter only of a patient in the analysis (independent data) and analyzing several catheters from the same patient (dependent data) by means of the generalized estimating equations (GEE) method. The main result of the study was based on the comparison of both statistical models.

Silver catheter study: methods and results of microbiological investigations

Within the framework of the clinical study of the Erlangen silver catheter 104 silver catheters and 105 control catheters were tested by microbiological culture. This was done by rolling the catheter on a blood agar plate, washing the lumen through with tryptic soy broth (TSB) and, after ultrasound treatment, incubating the catheter tip in TSB as an enrichment culture for detecting very low bacterial counts. There was good agreement in the numbers of colony-forming units (CFU) detected by the roll plate and luminal washout cultures in 92% of the silver and 89% of the control catheters tested. Seventy-six (73%) of the 104 silver catheters showed no bacterial growth and 16 (15%) showed very low bacteria counts (< 15 CFU), or growth only after enrichment, which were attributed in both instances to catheter contamination. Twelve catheter tips (12%) showed significant bacterial counts greater than 15 CFU which were indicative of colonization or catheter-related infection. Corresponding results in the control catheters were 59 (56%), 28 (27%) and 18 (17%), respectively, a higher rate of infection or contamination which was statistically significant (chi-square test: P = 0.04).

Reducing catheter-associated infections with silver-impregnated catheters in long-term therapy of children

Central venous long-term catheters offer reliable, large-lumen vascular access with high flow rates for delivery of nutrition or for cell-containing infusions and perfusions. Catheter-associated infections (CAI) pose the greatest threat to such vascular access, despite existing preventive measures. In this article one prospective and one retrospective study of CAI in pediatric therapy are presented. Study I: A retrospective investigation from 1990 through 1995 of 60 conventional long-term catheters in 50 patients. The total number of days in which the catheters were in place was 11,818. The calculated CAI incidence was 1 per 1,000 days of catheter insertion. Bacteriologically demonstrated CAI (identical isolate on the catheter tip and in a blood culture) occurred in three instances (5%). Five cases (8.3%) were diagnosed with a therapy-resistant, septic clinical picture. Study II: A prospective, randomized comparison of long-term silver-impregnated (Erlanger silver catheters) and control catheters (Quinton Instrument Co.) was made with 41 patients (20 with a silver catheter, 21 with a Quinton catheter). To date, the silver catheters have been distinguished by sterile bacteriological findings, whereas three cases of CAI have been demonstrated with the comparative catheters. One patient recently underwent intensive care after becoming unstable with signs of septic shock and demonstrable Pseudomonas aeruginosa, and two other patients manifested coagulase-negative staphylococci on the catheter tips. In three of nine control catheters an incidence of 1.18 per 1,000 days of indwelling catheters was found, whereas no CAI has occurred with the eight microbiologically tested silver catheters.

Catheter-associated infections in urology: possible use of silver-impregnated catheters and the Erlanger silver catheter

Indwelling urinary catheters play a very important part in urology. However, their use is accompanied by a considerable increase in the risk of nosocomial urinary tract infections. The pathophysiological cause is ascribed to pathogens that adhere to the catheter surface, proliferate and produce a biofilm. In addition to aseptic techniques, modification of the catheter material to confer antimicrobial activity plays an essential part in the prevention of catheter-related urinary tract infections. The antimicrobial efficacy of silver against gram-positive and gram-negative bacteria is well known and amply shown in vitro. The efficacy of silver-impregnated catheters is critically dependent on both the chemical structure of the incorporated silver and the way the silver has been combined with the basic catheter material. Hence, clinical studies on silver-modified catheters have so far given inconsistent results. The new technology of the Erlanger silver catheter offers the opportunity of an effective reduction in catheter-related infections.

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.

[Infectious diarrhea in routine pediatric practice]

Diarrhea, caused by infectious agents in childhood leads to dangerous loss of fluid and electrolytes. So the main issues in diagnosis and therapy are the evaluation of dehydration and the rapid compensation of deficits. The oral rehydration is superior to the parenteral as long as the clinical course allows. A infectious agent specific diagnosis and therapy is necessary only in well defined instances.