A silicone ventricular catheter coated with a combination of rifampin and trimethoprim for the prevention of catheter-related infections

Antibiotic impregnation and nanocoating of external ventricular drainage catheters for antibacterial applications: Evaluation of in vitro studies and molecular docking

The most suitable method to treat hydrocephalus disease is to insert a shunt catheter that drains the cerebral spinal fluid (CSF); however, shunt implantation is often associated with various bacterial infections. In this study, antibiotic-loaded nanospheres were prepared using the solvent evaporation technique and coated on an antibiotic-impregnated shunt surface to promote shunt antibacterial properties. Clindamycin (CDM) and rifampicin (RIF) were in combination loaded in a single nanosphere, whereas trimethoprim (TMP) was loaded individually in triblock copolymers [(d,l-lactide-random-ε-caprolactone)-block-poly(ethylene glycol)-block-(d,l-lactide-random-ε-caprolactone)] (PLEC). The drug-loading content, encapsulation efficiency, yield, size, and zeta potential of the antibiotic-loaded nanospheres were measured. The results showed that the drug-loading content of clindamycin- and rifampicin-loaded nanospheres (CDM/RIF-NPs) was approximately 3% and 8%, respectively, at a drug to polymer ratio of 1:2. In addition, trimethoprim-loaded nanospheres (TMP-NPs) showed nearly 7% drug loading at equal drug and polymer ratios. The amount of drug release was determined before and after the coating of nanospheres on the shunt surface. In addition, in silico molecular docking studies indicated the good chemical interaction of these antibiotics with PLEC, and the results were consistent with those of impregnation studies. Antibacterial tests of coated external ventricular drainage showed antibacterial activity for up to 21 days.

Modern Strategies in the Prevention of Implant-Associated Infections

The application of medical devices either for temporary or permanent use has become an indispensible part of almost all fields of medicine. However, foreign bodies are associated with a substantial risk of bacterial and fungal infections. Implant-associated infections significantly contribute to the still increasing problem of nosocomial infections.

To reduce the incidence of such infections, specific guidelines providing evidence-based recommendations and comprising both technological and nontechnological strategies for prevention have been established. Strict adherence to hygienic rules during insertion or implantation of the device are aspects of particular importance. Besides such basic and indispensable aspects, the development of new materials which could withstand microbial adherence and colonization has become a major topic in recent years. Modification of surface by primarily physico-chemical methods may lead to a change in specific and unspecific interactions with microorganisms and, thus, to a reduction in microbial adherence. Medical devices made out of a material that would be ideally antiadhesive or at least colonization-resistant would be the most suitable candidates to avoid colonization and subsequent infection. However, it appears impossible to create a surface with an absolute “zero”-adherence due to thermodynamical reasons and due to the fact that a modified material surface is in vivo rapidly covered by plasma and connective tissue proteins. Therefore, another concept for the prevention of implant-associated infections involves the impregnation of devices with various antimicrobial substances such as antibiotics, antiseptics, and/or metals.

In fact, already commercially available materials for clinical use such as antimicrobial catheters have been introduced, in part with considerable impact on subsequent infections. However, future studies are warranted to translate the knowledge on the pathogenesis of device-associated infections into applicable prevention strategies.

Comparative effectiveness of antibiotic-impregnated shunt catheters in the treatment of adult and pediatric hydrocephalus: analysis of 12,589 consecutive cases from 287 US hospital systems

OBJECT

The real-world effectiveness of antibiotic-impregnated shunt catheters to reduce the incidence of shunt infections is still debated. The literature to date consists mostly of small, single-institution studies. The aim of this study was to assess the incidence of infection for antibiotic-impregnated catheters (AICs) versus standard shunt catheters in a large nationwide administrative database.

METHODS

The authors retrospectively reviewed hospital discharge and billing records from the Premier Perspective Database from April 2003 to July 2009 to identify all adult and pediatric patients undergoing de novo ventricular shunt placement. The primary end point was the incidence of shunt infection within 1 year of implantation. Multivariate logistical regression was performed to determine factors associated with increased incidence of infection.

RESULTS

A total of 10,819 adult (AIC, 963; standard catheter, 9856) and 1770 pediatric (AIC, 229; standard catheter, 1541) patients underwent ventricular shunt placement in 287 US hospitals. Overall, the incidence of infection was 3.5% in adults (n=380) and 6.6% in pediatric patients (n=116). AICs were associated with significant reduction in infection for both adult (2.2% vs 3.6%, p=0.02) and pediatric (2.6% vs 7.1%, p<0.01) patients. AIC use was associated with reduced infection regardless of hospital size, annual shunt volume, hospital location, or patient risk factors and remained associated with a reduced infection in multivariate analysis for both adult (p=0.02) and pediatric (p=0.02) patients.

CONCLUSIONS

The use of antibiotic-impregnated shunt catheters was associated with a reduction in shunt infections for both adult and pediatric patients. This provides further support that AICs may represent a reliable means of reducing shunt infections for both adult and pediatric patients.

Numerical modelling and experimental investigation of drug release from layered silicone matrix systems

Medical devices and polymeric matrix systems that release drugs or other bioactive compounds are of interest for a variety of applications. The release of the drug can be dependent on a number of factors such as the solubility, diffusivity, dissolution rate and distribution of the solid drug in the matrix. Achieving the goal of an optimal release profile can be challenging when relying solely on traditional experimental work. Accurate modelling complementing experimentation is therefore desirable. Numerical modelling is increasingly becoming an integral part of research and development due to the significant advances in computer simulation technology. This work focuses on numerical modelling and investigation of multi-layered silicone matrix systems. A numerical model that can be used to model multi-layered systems was constructed and validated by comparison with experimental data. The model could account for the limited dissolution rate and effect of the drug distribution on the release profiles. Parametric study showed how different factors affect the characteristics of drug release. Multi-layered medical silicone matrices were prepared in special moulds, where the quantity of drug in each layer could be varied, and release was investigated with Franz-diffusion cell setup. Data for long-term release was fitted to the model and the full depletion of the system predicted. The numerical model constructed for this study, whose input parameters are the diffusion, effective dissolution rate and dimensional solubility coefficients, does not require any type of steady-state approximation. These results indicate that numerical model can be used as a design tool for development of controlled release systems such as drug-loaded medical devices.

The effect of self-assembled layers on the release behavior of rifampicin-loaded silicone

Providing a long period of sustained antibiotic release is one of the important challenges in the development of clinical shunts for long-term implantation. A cast-molding approach was used to load rifampicin into the silicone precursor before curing. Sustained in vitro release from rifampicin-loaded silicone for upwards of 110 days at a level of approximately 2-4 microg/cm2 per day was achieved. Quantitative comparisons of Staphylococcus epidermidis adhesion on untreated and rifampicin-loaded silicone surfaces were carried out to demonstrate the effect of rifampicin to discourage the bacterial adhesion. It was shown that the fresh 8.3% rifampicin-loaded silicone decreased bacterial adherence by 99.8%. Bacterial adherence on rifampicin-loaded silicone surfaces after 90 days release (eluted silicone) was decreased by 94.8%. A new approach was used to tune the initial burst effect and prolong long lasting release by introducing self-assembled perfluorodecyltrichlorosilane (FAS) and octadecyltrichlorosilane (OTS) layers. FAS layered structures can tune the burst effect and prolong the subsequent continuous release to achieve the long-term delivery. Significant decreases in initial burst effect (70.3% for multi-FAS layers and 39.7% for FAS monolayer) and enhanced long-term release (approx. 10 microg/cm2 per day for FAS monolayer for 110 days and approx. 15 microg/cm2 per day for multi-FAS layers for 60 days) were observed.

Comparison of Infection Rate With the Use of Antibiotic-Impregnated vs Standard Extraventricular Drainage Devices

BACKGROUND:

External ventricular drainage (EVD) catheters provide reliable and accurate means of monitoring intracranial pressure and alleviating elevated pressures via drainage of cerebrospinal fluid (CSF). CSF infections occur in approximately 9% of patients. Antibiotic-impregnated (AI) EVD catheters were developed with the goal of reducing the occurrence of EVD catheter-related CSF infections and their associated complications.

OBJECTIVE:

To present an international, prospective, randomized, open-label trial to evaluate infection incidence of AI vs standard EVD catheters.

METHODS:

Infection was defined as (1) proven infection, positive CSF culture and positive Gram stain or (2) suspected infection: (A) positive CSF culture with no organisms identified on initial Gram stain; (B) negative CSF culture with a gram-positive or -negative stain; (C) CSF leukocytosis with a white blood cell/red blood cell count &gt;0.02.

RESULTS:

Four hundred thirty-four patients underwent implantation of an EVD catheter. One hundred seventy-six patients in the AI-EVD cohort and 181 in the standard EVD catheter cohort were eligible for evaluation of infection. The 2 groups were similar in all clinical characteristics. Proven infection was documented in 9 (2.5%) patients (AI: 4 [2.3%] vs standard: 5 [2.8%], P = 1.0). Suspected infection was documented in 31 (17.6%) patients receiving AI and 37 (20.4%) patients receiving standard EVD catheters, P = .504. Duration of time to suspected infection was prolonged in the AI cohort (8.8 ± 6.1 days) compared with the standard EVD cohort (4.6 ± 4.2 days), P = .002.

CONCLUSION:

AI-EVD catheters were associated with an extremely low rate of catheter-related infections. AI catheters were not associated with risk reduction in EVD infection compared to standard catheters. Use of AI-EVD catheters is a safe option for a wide variety of patients requiring CSF drainage and monitoring, but the efficacy of AI-EVD catheters was not supported in this trial.

Cerebrospinal shunt infection in patients receiving antibiotic-impregnated versus standard shunts

OBJECT

Cerebrospinal fluid shunt infections are associated with significant morbidity and mortality in the treatment of adult and pediatric hydrocephalus. Antibiotic-impregnated shunt (AIS) catheters have been used with the aim of reducing shunt infection. While many studies have demonstrated a reduction in shunt infection with AIS, this reported efficacy has varied within the literature.

METHODS

The authors performed a systematic literature review to identify all published articles comparing the incidence of CSF shunt infection in AIS versus non-AIS catheters. The incidence of infection for AIS versus non-AIS catheters was calculated using the Mantel-Haenszel common odds ratio, and baseline demographics were compared between AIS and non-AIS cohorts.

RESULTS

Twelve AIS versus non-AIS cohort comparisons were identified in the literature (5 pediatric hydrocephalus, 3 adult hydrocephalus, and 4 mixed populations). In a total of 5613 reported shunt procedures (2664 AISs vs 2949 non-AISs), AISs were associated with a reduction in shunt infection (3.3% vs 7.2%; OR 0.439, p < 0.0001). In 787 shunt procedures for adult hydrocephalus (427 AIS vs 360 non-AIS), AISs were associated with reduction in shunt infection (0.9% vs 5.8%; OR 0.153, p < 0.0001). In 1649 shunt procedures for pediatric hydrocephalus (854 AIS vs 795 non-AIS), AISs were associated with reduction in shunt infection (5.0% vs 11.2%; OR 0.421, p < 0.0001).

CONCLUSIONS

The authors' systematic review of the literature demonstrates that AIS catheters are associated with a significant reduction over non-AIS catheters in the reported incidence of CSF shunt infection in adult and pediatric populations. The AIS catheters do not appear to be associated with an increased incidence of antibiotic-resistant microorganisms. Prospective, randomized trials are needed to firmly assess and confirm this apparent difference in infection incidence.

Hospital costs associated with shunt infections in patients receiving antibiotic-impregnated shunt catheters versus standard shunt catheters

BACKGROUND

The average hospital cost for shunt infection treatment is $50,000, making it the most financially costly implant-related infection in the United States. We set out to determine whether introduction of antibiotic-impregnated shunts (AISs) in our practice has decreased the incidence of shunt infection or decreased infection-related hospital costs at our institution.

METHODS

Clinical and hospital billing records of pediatric patients undergoing cerebrospinal fluid (CSF) shunt insertion at a single institution from April 2001 to December 2006 were retrospectively reviewed. Eighteen months before October 2002, all CSF shunts included standard, non-AIS catheters. During the 4 years after October 2002, all CSF shunts included AIS catheters. Patients were followed at least 18 months after surgery.

RESULTS

A total of 406 pediatric patients underwent 608 shunt placement procedures (400 AISs, 208 non-AISs). Of patients with non-AIS catheters, 25 (12%) experienced shunt infection, whereas only 13 patients (3.2%) with AIS catheters experienced shunt infection during follow-up (P < .001). The total hospital cost to treat 25 non-AIS shunt infections over the first 18 months was $1,234,928. The total hospital cost to treat 13 AIS shunt infections over the past 4 years was $606,328. The mean hospital cost per shunt infection was similar for infected AIS and non-AIS catheters ($46,640 vs. $49,397). However, the infection-related hospital cost per 100 patients shunted was markedly lower in the AIS cohort than in the non-AIS cohort ($151,582 vs. $593,715).

DISCUSSION

The introduction of AIS catheters in our institutional practice reduced the incidence of shunt infection and resulted in significant hospital cost savings. AIS systems are efficient and cost-effective instruments to prevent perioperative colonization of CSF shunt components.

Comparison of shunt infection incidence in high-risk subgroups receiving antibiotic-impregnated versus standard shunts

BACKGROUND

Shunt infection is a morbid complication of CSF shunting. Though antibiotic-impregnated shunt (AIS) systems decrease shunt infections by preventing bacterial colonization following device implantation, their effectiveness in populations at high risk for infection has recently been disputed. We set out to determine whether the categorical switch to AIS systems at our institution has resulted in a decreased incidence of shunt infection in high-risk pediatric patients.

METHODS

We retrospectively reviewed the records from all pediatric patients undergoing CSF shunt procedures at The Johns Hopkins Hospital over a 10-year period between January 1997 and December 2007. During the 5.75 years prior to October 2002, all CSF shunts included standard, non-AIS catheters. During the 4.25 years after October 2002, all CSF shunts included AIS catheters. High-risk subgroups were defined a priori as prematurity (<35 weeks gestational age), shunts placed immediately post-meningitis, conversion of external ventricular drains (EVD) to shunt, and replacement of nosocomial shunt infection in patients requiring prolonged hospital stay (>1 month).

RESULTS

A total of 544 pediatric patients underwent 1,072 shunt placement procedures (502 AIS, 570 non-AIS). Of patients with non-AIS catheters, 64 (11.2%) experienced shunt infection, whereas only 16 (3.2%) patients with AIS catheters experienced shunt infection (p<0.001). AIS versus non-AIS was associated with decreased shunt infection in premature neonates [three (5.5%) vs. seven (20.0%), p=0.030], acutely following bacterial meningitis [two (5.7%) vs. nine (25.0%), p=0.043], when converting EVD to shunts [zero (0%) vs. four (13.3%), p=0.030], and in patients with prolonged hospital stay>1 month [three (5.3%) vs. 12 (18.5%), p=0.022]. Staphylococcus aureus was the most common infectious agent for both non-AIS (81.3%) and AIS (75.0%) systems.

CONCLUSION

The introduction of AIS catheters into our institutional practice has reduced the incidence of shunt infection in pediatric populations at highest risk for infection. AIS catheters are effective instruments to prevent peri-operative colonization of CSF shunt components.

[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.

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.

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.

Bacteria and granulation tissue associated with Montgomery T-tubes

OBJECTIVES

Although complications (infection, development of granulation tissue) of silicone Montgomery T-tubes have been reported, the microbiological consequences and the origin of granulation tissue have not yet been evaluated.

STUDY DESIGN

A prospective trial.

METHODS

Twenty-three Montgomery T-tubes from 10 patients were analyzed with regard to the development of granulation tissue, bacterial growth (including genotyping with polymerase chain reaction), and results of sensitivity testing. Furthermore, stent sterilization (n = 6) was investigated.

RESULTS

Granulation tissue occurred with 74% of the stents, and all specimens showed signs of infection but no foreign body reaction. The predominant organisms were Staphylococcus aureus (35%) and Pseudomonas aeruginosa (17%). The differences between groups with and without granulation tissue were significant for P aeruginosa. Polymerase chain reaction fingerprinting of the S aureus obtained from 15 stents (n = 3 patients) revealed a total of seven different genotypes. Whereas two of these patients harbored six different genotypes of S aureus, the third patient was persistently colonized by S aureus over a 15-month period with the identical genotype. Susceptibility testing showed most commonly (65%) sensitivity to a combination of amoxicillin-clavulanate and ofloxacin. After sterilization, 92% of analyzed stent segments showed no bacterial growth.

CONCLUSIONS

Granulation tissue commonly occurred next to the silicone (subglottic area, stoma) where S aureus and P aeruginosa were commonly isolated. A combination of mechanical irritation and bacterial infection seems to account for the development of granulation tissue. Polymerase chain reaction fingerprinting showed both prolonged persistence and a change of colonizing strains after multiple stent replacements. A combination of amoxicillin-clavulanate and ofloxacin is the most effective antibiotic therapy. Sterilization of the cost-intensive silicone stents is feasible, and reuse in the same patient is justifiable from economic aspects.

Pharmaceutical strategies to prevent ventilator-associated pneumonia

The increasing incidence of hospital-acquired (nosocomial) infection is a disturbing phenomenon resulting in significant patient mortality and putting considerable strain on healthcare budgets and personnel. One particularly serious aspect of nosocomial infection is that of ventilator-associated pneumonia (VAP). This arises in patients who receive mechanical ventilation within the intensive care unit. The quoted incidence of VAP varies widely (5-67%) and the reported mortality of patients with VAP is in the range of 24-71%. This review will examine the many factors that account for these wide ranges reported, including the patient population under investigation, the causative organism, the method of diagnosis, interventions employed and preventative strategies. The use of bioactive and drug-impregnated biomaterials for endotracheal tube construction is discussed as novel approaches to the prevention of VAP.

Staphylococcus and biofilms

The genetic and molecular basis of biofilm formation in staphylococci is multifaceted. The ability to form a biofilm affords at least two properties: the adherence of cells to a surface and accumulation to form multilayered cell clusters. A trademark is the production of the slime substance PIA, a polysaccharide composed of beta-1,6-linked N-acetylglucosamines with partly deacetylated residues, in which the cells are embedded and protected against the host's immune defence and antibiotic treatment. Mutations in the corresponding biosynthesis genes (ica operon) lead to a pleiotropic phenotype; the cells are biofilm and haemagglutination negative, less virulent and less adhesive on hydrophilic surfaces. ica expression is modulated by various environmental conditions, appears to be controlled by SigB and can be turned on and off by insertion sequence (IS) elements. A number of biofilm-negative mutants have been isolated in which polysaccharide intercellular adhesin (PIA) production appears to be unaffected. Two of the characterized mutants are affected in the major autolysin (atlE) and in D-alanine esterification of teichoic acids (dltA). Proteins have been identified that are also involved in biofilm formation, such as the accumulation-associated protein (AAP), the clumping factor A (ClfA), the staphylococcal surface protein (SSP1) and the biofilm-associated protein (Bap). Concepts for the prevention of obstinate polymer-associated infections include the search for new anti-infectives active in biofilms and new biocompatible materials that complicate biofilm formation and the development of vaccines.