Development of a new CSF-shunt with sustained release of an antimicrobial broad-spectrum combination

A Multicenter Multinational Registry for Assessing Ventriculoperitoneal Shunt Infections for Hydrocephalus

BACKGROUND:

Reported infection rates after ventriculoperitoneal shunt surgery vary from 1 to 25%. Antibiotic-impregnated (AI) catheters may reduce shunt infection rates, but this is uncertain.

OBJECTIVE:

To establish a prospective shunt registry to evaluate short-term (3-month) infection rates associated with ventriculoperitoneal shunts and standard or AI catheters during surgical treatment of hydrocephalus.

METHODS:

A prospective, multicenter, noncontrolled, open-label registry investigated patients with de novo catheter implantation or catheter replacement of an existing ventriculoperitoneal shunt. The primary outcome was shunt infection.

RESULTS:

A total of 440 patients were entered into the registry at 10 sites: 3 in North America, 2 in Singapore, 4 in China and 1 in India. Seven patients were excluded. Of the 433 remaining patients, 314 had new shunts and 119 were revisions. Shunt infections occurred in 14 of 433 patients (3.2%) overall and in 2 of 37 infants (5.2%) younger than 1 year. AI catheters were used in 46 of 433 patients at 7 centers. The shunt infection rate was 0 of 46 for shunts with AI catheters and 14 of 387 (3.6%) without AI catheters. Infection rates were similar with AI catheters, adjusting for age and catheter type.

CONCLUSION:

The overall shunt infection rate was lower than in previous multicentered studies. The low infection rate and low rate of AI catheter use precludes any meaningful statement regarding the value of AI catheters in reducing the infection rate. Consideration should be given to performing a well designed, adequately powered, prospective randomized controlled trial to determine whether AI catheters reduce shunt infection rates.

[Effect of antibiotic-impregnated catheters on the incidence of infection after cerebrospinal fluid shunting]

BACKGROUND AND OBJECTIVE

Infection is a major complication after cerebrospinal fluid (CSF) shunt systems insertion. Antibiotic-impregnated (AI) catheters seem to reduce infection rate in clinical practice. The objective of this study was to determine if the use of AI catheters reduces Staphylococcus spp. infection rate, as it is the most commonly isolated organism.

PATIENTS AND METHOD

Authors retrospectively reviewed all patients who underwent rifampin-impregnated and clindamycin-impregnated catheters at our hospital. These included external ventricular catheters (inserted from January 2006 to January 2007) and internalized shunts (inserted from January 2004 to January 2007). They also reviewed patients who underwent insertion of non-impregnated external catheters and internalized shunts during the same periods. Overall infection rate, Staphylococcus spp. infection rate and gram negative bacilli infection rate were compared in both groups by means of chi2 test.

RESULTS

Sixty-five procedures with AI catheters and 66 procedures with non-AI catheters were performed. Overall infection rate as well as Staphylococcus spp. infection rate were significantly lower in the AI catheters cohort (p = 0.046 and p = 0.029, respectively), without increasing gram negative bacilli infections.

CONCLUSIONS

The use of rifampin and clindamycin-impregnated catheters is a useful tool to reduce Staphylococcus spp. infections after CSF shunting procedures. However, future clinical trials are required to confirm these results.

Clinical and economic consequences of antibiotic-impregnated cerebrospinal fluid shunt catheters

OBJECT

The authors evaluated the safety and efficacy of antibiotic-impregnated shunt catheters (AISCs) and determined the cost-benefit ratio related to the fact that AISCs increase the implant costs of a shunt procedure by approximately $400 per patient.

METHODS

The control group comprised 98 adults with chronic hydrocephalus and 22 children, who were treated without AISCs (non-AISCs). In the treatment group, AISCs (Bactiseal, Codman, Johnson & Johnson) were implanted in 171 adults and 26 children. The minimum follow-up period was 6 months.

RESULTS

Important risk factors for shunt infections (such as age, comorbidity, cause of hydrocephalus, operating time, and duration of external cerebrospinal fluid drainage prior to shunt placement) did not differ between the study and control groups. In the pediatric AISC group, the frequency of premature, shunt-treated infants and the incidence of external ventricular drainage prior to shunt insertion were actually higher than those in the non-AISC group. When using AISCs, the shunt infection rate dropped from 4 to 0.6% and from 13.6 to 3.8% in the adult and the pediatric cohort, respectively. Overall the infection rate decreased from 5.8 to 1%, which was statistically significant (p = 0.0145). The average costs of a single shunt infection were $17,300 and $13,000 in children and adults, respectively. The cost-benefit calculation assumed to have saved shunt infection-related costs of approximately $50,000 in 197 AISC-treated patients due to the reduction in shunt infection rate in this group compared with costs in the control group. Despite the incremental implant costs associated with the use of AISCs, the overall reduction in infection-related costs made the use of AISCs cost beneficial in the authors' department.

CONCLUSIONS

From clinical and economic perspectives, AISCs are seemingly a valuable addition in hydrocephalus therapy.

Antibiotic-impregnated shunt catheters for the treatment of infantile hydrocephalus

INTRODUCTION

Antibiotic-impregnated shunt (AIS) components decrease shunt infections by preventing bacterial colonization that occurs during implantation. Despite studies showing improved efficacy in preventing infection however, concern still exists regarding using AIS components in infants, especially premature ones. In this study, clinical outcomes were assessed in infants with hydrocephalus (<1 year) following AIS placement.

METHODS

A prospective observational study was conducted involving pediatric patients <1 year of gestational age with hydrocephalus who underwent placement of AIS components (ventriculoperitoneal, ventriculoatrial, and cystoperitoneal) as initial treatments, shunt revision surgery, or following previous placement of a ventricular access device (VAD, Rickman reservoir). Measured outcomes included: infection, shunt revision surgery, and complications.

RESULTS

Seventy-four infants underwent 108 AIS procedures, and all were followed for over 9 months. Twenty-seven patients (36.5%) possessed previous VADs. Average weight and gestational age at birth were 1,976 g (range: 560-3,500 g) and 32.8 weeks (range: 23-41 weeks), respectively. The average age at the time of surgery was 14.6 weeks (range: 1 day to 50 weeks). Five infections occurred in 5 patients (4.6% of procedures, 6.75% of patients), 60% of which were very premature (<32 weeks). Thirty-three patients (44.6%) required shunt revision surgery, 5 (15%) for infection and 28 (85%) for malfunction. Three cerebrospinal fluid leaks occurred perioperatively without significant sequelae, and no mortalities occurred from the procedures.

CONCLUSION

AIS systems can safely be used to treat hydrocephalus in pediatric patients <1 year old, even for those with a history of prematurity. One possible therapeutic application for such premature patients may be the incorporation of antibiotic impregnation into VADs or ventriculosubgaleal components to treat infants with hydrocephalus prior to definitive CSF shunt placement.

Prolonged exposure to antibiotic-impregnated shunt catheters does not increase incidence of late shunt infections

OBJECTIVE

Antibiotic-impregnated shunt (AIS) systems have been designed to prevent the colonization of shunt components by skin flora that occurs at surgery. Although such systems may decrease the incidence of early shunt infections (those occurring within 6 months of shunt placement), it is unclear if such exposure to prolonged antibiotics leads to an increased incidence or virulence of late shunt infections (those occurring later than 6 months after shunt placement). In this study, the authors evaluate the incidence of late shunt infection after the introduction of an AIS system in a pediatric hydrocephalus population.

MATERIALS AND METHODS

We prospectively reviewed all pediatric patients undergoing antibiotic-impregnated CSF shunt insertion or shunt revision operations at our institution for the 33 month period between October 1, 2002 and June 31, 2005. All shunt-related complications, including shunt infection, were evaluated in those patients with later than 6 months of follow-up.

RESULTS

A total of 153 pediatric patients (between 1 and 21 years of age) underwent 262 shunting procedures involving the use of antibiotic-impregnated catheters. All patients were followed-up for later than 6 months with a mean follow-up of 21.7 months (range 13-46 months). Ten patients (3.82%) experienced an early shunt infection within the 6-month follow-up period. No patients experienced a late shunt infection.

CONCLUSION

Although concern exists that AIS systems may delay shunt infections or even increase the rate or virulence of such infections, introduction of such catheters into a pediatric hydrocephalus cohort does not significantly increase incidence of late CSF shunt infection compared to historic controls.

Lack of efficacy of antibiotic-impregnated shunt systems in preventing shunt infections in children

OBJECTIVE

Shunt infection is a common and serious complication of cerebrospinal fluid (CSF) shunting most commonly caused by skin flora contamination at surgery. Recent studies indicate that the use of antibiotic-impregnated (AI) shunt systems may reduce the risk of postoperative shunt infections. We evaluated the incidence of shunt infections associated with the use of AI shunt catheters and compared it with the incidence associated with standard non-AI catheters.

MATERIALS AND METHODS

All shunt procedures performed by one surgeon using AI catheters were reviewed. An equal number of consecutive shunt procedures performed by the same surgeon using non-AI catheters were reviewed from the period immediately before the introduction of the AI system. Patients with <9 months of follow-up were excluded; all shunt infections and shunt-related complications were recorded. The proportions of infected shunts in the AI and control groups were compared using a chi (2) analysis.

CONCLUSION

We reviewed 160 shunt procedures (80 per group). The infection rate was 5.0% among patients with AI catheters compared with 8.8% in the control group (P = 0.534, Fischer's exact). The average time to infection was similar between the two groups. Among the AI group, the shunt infection rate did not differ between ventricular catheter, distal catheter revisions, and revisions of ventricular and peritoneal tubing. In contrast with other reports, we found no significant reduction in the pediatric CSF shunt infection rate with the use of AI shunt systems. Any recommendation for or against the routine use of AI systems in children requires a prospective, blinded, randomized-controlled trial with adequate power.

Effect of cast molded rifampicin/silicone onstaphylococcus epidermidis biofilm formation

Infection is one of the most common catheter-related complications, especially in shunt systems used to treat hydrocephalus. Staphylococcus epidermidis is directly related to biomaterial infections owing to its ability to form a biofilm on implanted materials. In this study, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to investigate the effect of the antibiotic rifampicin on the colonization and growth of S. epidermidis 35984 on the surface of silicone. A cast molding method was used to load rifampicin into the silicone precursor before it was cured. Bacteria with a diameter of 800-1000 nm and height of 200-500 nm were found to be embedded in the biofilm. Compact multilayer biofilm structures were found on silicone surfaces upon incubation for 4 and 24 h. On the other hand, sparser biofilm structures were observed on rifampicin-loaded surfaces after incubation for the same duration. Deformation of bacteria was observed by AFM. Moreover, different bacterial colony structures on the surfaces of silicone and rifampicin-loaded silicone were observed by AFM and SEM.

Initial experience with antibiotic-impregnated silicone catheters for shunting of cerebrospinal fluid in children

INTRODUCTION

Infection is a major complication of cerebrospinal fluid (CSF) shunting procedures. Recently, rifampin-impregnated and clindamycin-impregnated silicone catheters have been developed in an attempt to prevent and/or reduce the incidence of shunt infections. In vitro and in vivo animal studies have shown their efficacy in reducing bacterial colonization of catheters. However, these shunts are yet to be evaluated in clinical trials and their safety and efficacy in preventing shunt infections is unknown.

METHODS

Between April 2002 and April 2003, 31 children (age range 6 months to 17 years, mean 4.5 years) underwent implantation of an antibiotic-impregnated silicone catheter for CSF diversion. All surgeries were performed by a single neurosurgeon (HSM) at a single medical center. The Codman Hakim Bactiseal silicone catheter was used in all children. Thirty-two catheters were implanted in 31 children. All children have been followed since surgery (for an average of 19 months). For comparison, the previous 46 standard implanted shunts over a similar period of time were reviewed (average follow-up 31 months).

RESULTS

Of the 32 implanted catheters, 11 involved placement of a new complete shunt system, 8 were distal revisions, and 13 were proximal/ventricular revisions. There were fewer early and late complications than in the standard shunt group (12.5 and 18.8% vs. 23.9 and 34.8%). There was no local reaction from implantation of the catheters. One child contaminated his distal catheter by disrupting his abdominal incision. None of the other patients have developed any evidence of shunt infection to date.

CONCLUSION

Rifampin-impregnated and clindamycin-impregnated silicone catheters appear to be safe and well tolerated in children. Preliminary results suggest a low incidence of shunt infection. Longer follow-up and a larger number of patients are needed to more accurately assess the efficacy of these catheters compared with traditional silicone catheters.

Novel strategies to prevent catheter-associated infections in oncology patients

Aggressive cytotoxic treatment of cancer contributes to the growing number of life-threatening infections. Vascular catheters create predominant risks for staphylococcal, enterococcal and candida blood stream infections. Although the contaminating microorganisms may be few in number, the altered host immune response in the presence of such implants as well as disease-associated immunosuppression implies that even small bacterial counts have to be regarded as highly virulent species. Diagnosis of catheter-related infection (CRI) remains difficult before withdrawal of the suspected catheter. Positive culture of catheter surface, lumen and hub and positive peripheral blood probes (paired quantitative blood culture) are predictive for catheter related bacteremia (CRB). Diligent catheter care and effective antimicrobial catheters may reduce prolonged hospital stay, increased morbidity or mortality and serious economical consequences. The most promising approach features the incorporation of antimicrobial drugs into the polymer matrices that entrap but do not bind the drugs, allowing for extended release. For the efficacious prevention of colonization in the microenvironment of the implantable device the concentration of the antimicrobial substances must exceed usual antibiotic concentrations by a thousand-fold. This is the desired effect--high concentration near the device surface and very low systemic concentration. Incorporation of antimicrobials in the bulk material that constitutes a device can be effective as shown in several in vitro and in vivo studies. In the future, modification of both short-term and long-term catheters by biofilm-active antimicrobials creating slow delivery systems may provide an effective method to protect patients from nosocomial infection in oncology.

Measurement of ultrasonic-induced chlorhexidine liberation: correlation of the activity of chlorhexidine-silver-sulfadiazine-impregnated catheters to agar roll technique and broth culture

The diagnosis of intravascular catheter-related infections continues to be a challenge to both the clinician and the microbiologist. To assess the antiseptic effects of silver-sulfadiazine-chlorhexidine-impregnated central venous catheters (SSC) on catheter culture systems, segments of fresh antiseptic- and non antiseptic-impregnated catheters as well as extracted catheters following five days of immersion in PBS were sonicated. The chlorhexidine liberated from the catheter material by ultrasonication was measured by HPLC. Fresh antiseptic-impregnated catheter segments rolled on seeded agar plates produced inhibition zones unlike catheters which had been extracted for >five days in phosphate buffered saline (PBS). Scanning electron microscopy (SEM) revealed that chlorhexidine-silversulfadiazine crystals were located in the superficial catheter matrix. Direct contact of superficially located drug particles with seeded agar plates probably caused the inhibition of bacterial growth. The study suggests that antiseptic compounds readily elute from fresh catheters during solid medium-based culturing processes and ultrasonication. The addition of inhibitors of silversulfadiazine-chlorhexidine to media may be prudent especially when culturing antimicrobial loaded catheters removed after short inwelling times.

Antibacterial activity of antibiotic-soaked polyvinylpyrrolidone-grafted silicon elastomer hydrocephalus shunts

If shunts, inserted for the relief of hydrocephalus, are pretreated with antimicrobials, the incidence of shunt-associated infections (SAI) may be reduced. The duration of the antibacterial activity of shunts, made from conventional silicon elastomer (SE) or from SE grafted with the hydrogel polyvinylpyrrolidone (SEpvp), which had been soaked in various antibiotics, was assessed in vitro. For any antibiotic or combination, using an arbitrary breakpoint (aBP), SEpvp remained antibacterially active for longer periods than SE. Bacterial adherence to either shunt was prevented during the period of antibacterial activity. Thus, the aBP is a good indicator of the capacity of antimicrobial-treated shunts to prevent bacterial colonization in vitro. Hydrogel-grafting of shunts may be useful in preventing SAI.

Polyurethane coatings release bioactive antibodies to reduce bacterial adhesion

This study describes the formulation of a biomedical grade polyurethane hydrogel coating containing solid dispersed bioactive antibodies cast from an organic solvent onto a model polymer biomaterial substrate. A prepolymer dispersion in anhydrous isopropanol containing a uniformly distributed slurry of 22 microm sieved commercial lyophilized polyclonal pooled human immunoglobulin G (IgG) solids was coated onto polymer substrates by simple immersion. Maximum antibody release was approximately 50 microg/cm(2) from a 15% w/w IgG polymer coating. In vitro antimicrobial studies utilized Escherichia coli to compare performance of bare uncoated tubing, hydrogel-coated tubing with added aqueous phase antibodies, and antibody-dispersed hydrogel-coated tubing. Bacterial adhesion was reduced significantly (p<0.05) in the presence of antibodies with the greatest reduction seen with the antibody releasing coating. The presence of antibody also significantly enhanced the killing of the bacteria in an in vitro opsonophagocytic assay using freshly isolated blood neutrophils over 2 h indicating that antibody bioactivity is maintained. This controlled release polyurethane hydrogel coating imparts infection resistance by exploiting the low adhesive properties of the biomedical grade hydrogel and the intrinsic bioactive role of the antibodies to reduce bacterial adhesion and promote clearance via natural immune mechanisms.

Antimicrobial substances and effects on sessile bacteria

Biofilms occur in natural aquatic ecosystems and on surfaces of biomaterials. They are generally associated with clinical infections predominantly of prosthetic hip joints, heart valves and catheters. Sessile microorganisms may be intimately associated with each other and to solid substratum through binding to and inclusion into exopolymer matrices on biofilms. The establishment of functional colonies within the exopolymeric matrices generate physico-chemical gradients within biofilms, that modify the metabolism and cell-wall properties of the microorganism. A consequence of biofilm growth is an enhanced microbial resistance to chemical antimicrobial agents and antibiotics. Investigations on the antimicrobial efficacy of antibiotics, antiseptics and antimicrobial heavy ions, however, gave controversial results. No single antimicrobial substance has been developed for the efficient eradication of adherent bacteria. This review elucidates the mechanisms of microbial resistance in biofilms and strategies for the prevention of biofilm development. Pharmacokinetical and pharmacodynamical issues for the screening of biofilm-active drugs are presented. Combinations of antistaphylococcal antibiotics with rifampin may be advantageous for preventing and curing biomaterial infections.

Killing effects of antibiotics and two-fold antimicrobial combinations on proliferating and non growing staphylococci

Antimicrobial agents are generally tested against bacteria in the log phase of multiplication to produce the maximal bactericidal effect. In case of foreign body infections, bacteria may multiply less optimally. We examined the effects of several classes of lipophilic antistaphylococcal agents to determine their antimicrobial activity towards coagulase-positive and coagulase-negative staphylococci during the non-growing and slowly growing phases. Only two-fold combinations containing rifampicin were bactericidal (3-log kill) against Staphylococcus aureus. This was in contrast to growing bacteria in the log phase, in which a variety of antibiotics produced relevant killing. Concerning the staphylococci examined, antibiotic killing was greatly dependent on the growth rate. Most of the two-fold combinations containing rifampicin showed additive and synergistic antibacterial activity both in growth and stationary states as measured by the killing kinetics. The theoretical and clinical implications of delayed killing by chemotherapeutic agents for established bacterial infections and infections involving foreign bodies are discussed. Antimicrobial combinations including rifampicin and a second lipophilic antistaphylococcal drug may be most promising and appropriate as coating substances for intravascular devices or for clinical application in cases of implant infections.