Bacterial adhesion to cerebrospinal fluid shunts

A search for bacteria identified from cerebrospinal fluid shunt infections in previous surgical events

Shunt infections are a common complication when treating hydrocephalus by cerebrospinal fluid (CSF) shunt placement. The source of infecting pathogens is not well understood. One hypothesis, which we explored here, is that microorganisms persist chronically in the host long before a symptomatic infection occurs and may be detectable in surgical events preceding infection. A cohort of 13 patients was selected, for which CSF samples were available from an infection episode and from a previous surgery event, which was either an initial shunt placement or a revision. Microbiota were analyzed both directly from CSF and from isolates cultured from CSF on aerobic and anaerobic media. The detection and identification of bacteria was done with high throughput DNA sequencing methods and mass spectrometry. The presence of bacteria was confirmed in 4 infection samples, of which 2 were after initial placement and 2 after revision surgery. Taxonomic identification was consistent with clinical microbiology laboratory results. Bacteria were not detected in any of the CSF samples collected at the time of the previous surgical events. While our findings do not provide direct evidence for long-term persistence of pathogens, they suggest the need for consideration of additional source material, such as biofilm and environmental swabs, and/or the use of more sensitive and specific analytical methods.

Efficacy of postoperative antibiotic injection in and around ventriculoperitoneal shunt in reduction of shunt infection: A randomized controlled trial

OBJECTIVES

Infection is a common complication of ventriculoperitoneal (VP) shunt surgery. The incidence of shunt infection is still high despite routine administration of perioperative antibiotics. A lower incidence of shunt infection was observed when antibiotic-impregnated shunts (AIS) were used to treat hydrocephalus and a rapid cure was reported in cases of ventriculitis when antibiotics were injected into external ventricular drain (EVD). That is why we theorized that postoperative prophylactic injection of antibiotics in and around the shunt hardware would reduce the incidence of shunt infection.

PATIENTS AND METHODS

A randomized controlled clinical trial where 60 patients up to one year old, diagnosed with congenital hydrocephalus and submitted to VP shunt insertion, were randomly assigned to one of 3 groups. The treatment groups received the conventional perioperative antibiotics in addition to vancomycin and gentamicin injection in the reservoir and around the peritoneal catheter either once (group A) or twice (group B), while the control group (C) received only the conventional perioperative antibiotics. Cases were followed-up for up to 1 year.

RESULTS

The majority of patients were less than 1 month old. The follow-up period ranged from 2 to 12 months with a mean of 8.9 months. The mean duration of onset of infection after surgery was 30 days. Prematurity (p=0.00236), age less than one month (p<0.0001) and duration of surgery of 90 min or more (p<0.00001) were significant risk factors for postoperative shunt infection. Significantly more cases of shunt infection occurred within one month after surgery (p=0.021). The control group had significantly more cases of postoperative shunt infection than the treatment groups (p=0.0042).

CONCLUSIONS

In congenital hydrocephalus patients submitted to VP shunt insertion, injection of prophylactic vancomycin and gentamicin in and around the shunt hardware significantly reduced the incidence of postoperative shunt infection.

Evaluation of microbial bacterial and fungal diversity in cerebrospinal fluid shunt infection

Background

Cerebrospinal fluid shunt infection can be recalcitrant. Recurrence is common despite appropriate therapy for the pathogens identified by culture. Improved diagnostic and therapeutic approaches are required, and culture-independent molecular approaches to cerebrospinal fluid shunt infections have not been described.

Objectives

To identify the bacteria and fungi present in cerebrospinal fluid from children with cerebrospinal fluid shunt infection using a high-throughput sequencing approach, and to compare those results to those from negative controls and conventional culture.

Methods

This descriptive study included eight children ≤18 years old undergoing treatment for culture-identified cerebrospinal fluid shunt infection. After routine aerobic culture of each cerebrospinal fluid sample, deoxyribonucleic acid (DNA) extraction was followed by amplification of the bacterial 16S rRNA gene and the fungal ITS DNA region tag-encoded FLX-Titanium amplicon pyrosequencing and microbial phylogenetic analysis.

Results

The microbiota analyses for the initial cerebrospinal fluid samples from all eight infections identified a variety of bacteria and fungi, many of which did not grow in conventional culture. Detection by conventional culture did not predict the relative abundance of an organism by pyrosequencing, but in all cases, at least one bacterial taxon was detected by both conventional culture and pyrosequencing. Individual bacterial species fluctuated in relative abundance but remained above the limits of detection during infection treatment.

Conclusions

Numerous bacterial and fungal organisms were detected in these cerebrospinal fluid shunt infections, even during and after treatment, indicating diverse and recalcitrant shunt microbiota. In evaluating cerebrospinal fluid shunt infection, fungal and anaerobic bacterial cultures should be considered in addition to aerobic bacterial cultures, and culture-independent approaches offer a promising alternative diagnostic approach. More effective treatment of cerebrospinal fluid shunt infections is needed to reduce unacceptably high rates of reinfection, and this work suggests that one effective strategy may be reduction of the diverse microbiota present in infection.

Use of quantitative 16S rRNA PCR to determine bacterial load does not augment conventional cerebrospinal fluid (CSF) cultures among children undergoing treatment for CSF shunt infection

The aim of this study was to develop a quantitative 16S rRNA assay for determination of bacterial nucleic acid load in cerebrospinal fluid (CSF) shunt infection and to compare quantitative 16S rRNA polymerase chain reaction (PCR) findings to those of conventional bacterial culture in patients treated for CSF shunt infection. We developed a quantitative 16S rRNA PCR assay that detected bacterial load across a range of 2.5 × 10(9) down to 2.5 × 10(4) 16S copies/mL CSF under experimental conditions for numerous Gram-positive and Gram-negative organisms. However, when applied to archived CSF samples from 25 shunt infection episodes, correlations between positive bacterial culture and 16S rRNA levels were seen in only half of infections, and 16S rRNA levels dropped precipitously after an initial peak on the first day of sample collection. Bacterial load measured using 16S rRNA PCR does not provide sufficient information beyond bacterial culture to inform CSF shunt infection treatment.

The use of the ASET in the diagnosis of ventriculoatrial shunt infection

A 38-year-old man with a ventriculoatrial shunt presented with non-specific symptoms (headache, back pain, night sweats) and inconclusive laboratory results. He showed an extremely high titre of antibody to Staphylococcus epidermidis which proved diagnostic of shunt infection. This was confirmed on shunt removal and he was successfully treated.

Endoscopic observations of blocked ventriculoperitoneal (VP) shunt: a step toward better understanding of shunt obstruction and its removal

OBJECTIVES

Most of our understanding of ventriculoperitoneal (VP) shunt blockage (ventricular end) is based on in vitro studies of blocked VP shunts. Not much information is available regarding the in vivo changes that occur in the tube and in the surrounding ventricle. The primary aim of our study was to observe and analyse these changes, directly, through the endoscope, in patients with blocked shunts undergoing an endoscopic third ventriculostomy (ETV). Based on these findings, we have also suggested criteria for safe removal of the VP shunt tube following ETV.

MATERIAL AND METHODS

ETV was performed with standard technique in patients with blocked VP shunt. The ventricular end of the shunt tube was inspected through the endoscope, for changes in ventricle linings as well as in the shunt tube. These changes were correlated with the age of the patient, etiology of HC, type or make of the shunt tube, duration of shunt placement to ETV and the CSF findings.

RESULTS

Fifty-three patients of blocked VP shunt underwent ETV from July 2006 to April 2010. Thirty patients had Chhabra (CH) V P Shunt (Surgiwear, India) and 23 had ceredrain (CD) shunt (Hindustan Latex, India). The age of the patients ranged from 2 months to 60 years (mean--13.33 years.). Various causes of hydrocephalus (HC) included congenital hydrocephalus (aqueductal stenosis) in 18 patients, post-meningitis hydrocephalus (PMH) in 32 cases, neuro-cysticercosis (NCC) in 2 patients and intraventricular haemorrhagic (IVH) in 1 patient. Clinical and radiological improvement occurred in 33 (62.21%), and 24 (45%) patients, respectively. Freedom from shunt was attained in 20 (38%) patients. The changes around the shunt tube were seen in 41 (77%). Hyperaemia and neovascularised ependyma was seen in 20 (37%) and 15 (28%) patients. Encasement of the tube was seen in 41%. Ependymal growth and neovascularised shunt tubes were noticed in 15% each. Choroid plexus blocking the tube was seen in only four cases (7%). VP shunt was revised in 14 patients (26.4%). Patient with infective etiology had more changes (p < 0.005). Age, CSF findings and make of shunt tube had no relation with endoscopic observations (p< 0.02).

CONCLUSIONS

ETV has a role in shunt failures. It can offer patient a chance of shunt free life. Endoscopic observation of shunt tube and ventricle can unfold several interesting in vivo findings pertaining to shunt obstruction. Shunt should only be removed if there are no adhesions and neovascularisation.

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.

Action of linezolid or vancomycin on biofilms in ventriculoperitoneal shunts in vitro

Cerebrospinal fluid (CSF) shunts used to treat hydrocephalus have an overall infection rate of about 10% of operations. The commonest causative bacteria are Staphylococcus epidermidis, followed by Staphylococcus aureus and enterococci. Major difficulties are encountered with nonsurgical treatment due to biofilm development in the shunt tubing and inability to achieve sufficiently high CSF drug levels by intravenous administration. Recently, three cases of S. epidermidis CSF shunt infection have been treated by intravenous linezolid without surgical shunt removal, and we therefore investigated vancomycin and linezolid against biofilms of these bacteria in vitro. A continuous-perfusion model of shunt catheter biofilms was used to establish mature (1-week) biofilms of Staphylococcus aureus, Staphylococcus epidermidis (both methicillin resistant [MRSA and MRSE]), Enterococcus faecalis, and Enterococcus faecium. They were then "treated" with either vancomycin or linezolid in concentrations achievable in CSF for 14 days. The biofilms were then monitored for 1 week for eradication and for regrowth. Enterococcal biofilms were not eradicated by either vancomycin or linezolid. Staphylococcal biofilms were eradicated by both antibiotics after 2 days and did not regrow. No resistance was seen. Linezolid at concentrations achievable by intravenous or oral administration was able to eradicate biofilms of both S. epidermidis (MRSE) and S. aureus (MRSA). Neither vancomycin at concentrations achievable by intrathecal administration nor linezolid was able to eradicate enterococcal biofilms. It is hoped that these in vitro results will stimulate further clinical trials with linezolid, avoiding surgical shunt removal.

Linezolid treatment of shunt-related cerebrospinal fluid infections in children

OBJECT

The emergence of multidrug-resistant bacteria as a cause of ventriculoperitoneal (VP) shunt infection is a disconcerting phenomenon that often requires the use of alternative antimicrobial agents due to resistance against commonly used medications. Linezolid, a member of a new class of antimicrobial agents, has good activity against virtually all important gram-positive pathogens, including multidrug-resistant gram-positive pathogens. The object of this article is to report a single-center experience with linezolid treatment in 6 young patients with VP shunt infections caused by drug-resistant strains.

METHODS

The authors reviewed the records of 6 pediatric patients who developed VP shunt infection and in whom initial antimicrobial treatment regimens, including vancomycin, either failed or were associated with vancomycin-resistant enterococcus. All 6 patients were treated at their hospital between July 1, 2008, and June 29, 2009. The patients' demographic and clinical characteristics, underlying diseases, clinical manifestations, laboratory results, and various treatment modalities used before linezolid therapy were evaluated.

RESULTS

The 6 patients included were 2 boys and 4 girls with a mean (+/- SD) age of 11.83 +/- 12 months (range 4-36 months). Five patients had acquired an infection within 4 months (mean 7.50 +/- 13.51 months, range 1-35 months) after shunt insertion. Four patients were treated with external ventricular drainage. Two patients' parents refused to allow shunt removal and placement of an external ventricular drain. The CSF was clear of bacterial growth within a mean of 3.67 +/- 1.36 days (range 2-6 days) after initiation of linezolid treatment. The mean duration of linezolid treatment was 18.17 +/- 3.31 days (range 14-21 days). Microbiological clearance of CSF and clinical cure were achieved in all patients. No laboratory or clinical side effects were observed during the treatment period. The mean length of hospital stay was 22.8 +/- 4.96 days (range 17-28 days).

CONCLUSIONS

Linezolid could be an appropriate treatment alternative in children with ventriculostomy-related CSF infections caused by drug-resistant strains, including cases in which shunt removal is not an option. Well-designed prospective studies providing additional information on linezolid levels in plasma and CSF are necessary to confirm the authors' observations.

An experimental in-vivo canine model for adult shunt infection

Background

Detailed human studies of the mechanisms and development of shunt infection in real time are not possible, and we have developed a canine hydrocephalus model to overcome this. The intention of this pilot study was to show that the canine hydrocephalus model could be shunted using conventional "human" shunts, and that a shunt infection could be established so that further studies could then be planned.

Methods

Hydrocephalus was induced in seven dogs (Canis familiaris) by fourth ventricle obstruction. Four weeks later they were shunted using a Hakim Precision valve. Four of the dogs received shunts whose ventricular catheter had been inoculated with Staphylococcus epidermidis, and three were uninoculated controls. Four weeks after shunting the dogs were sacrificed and necropsy was performed. Removed shunts and tissue samples were examined microbiologically and isolates were subjected to detailed identification and genomic comparison.

Results

All the dogs remained well after shunting. Examination of removed shunt components revealed S. epidermidis in the brain and throughout the shunt system in the four inoculated animals, but in two of these Staphylococcus intermedius was also found. S. intermedius was also isolated from all three "negative" controls. There were slight differences between S. intermedius strains suggesting endogenous infection rather than cross- infection from a point source.

Conclusion

Shunt infection was established in the canine model, and had the experiment been extended beyond four weeks the typical microbiological, pathological and clinical features might have appeared. The occurrence of unplanned shunt infections in control animals due to canine normal skin flora reflects human clinical experience and underlines the usual source of bacteria causing shunt infection.

Biomaterials for the central nervous system

Biomaterials are widely used to help treat neurological disorders and/or improve functional recovery in the central nervous system (CNS). This article reviews the application of biomaterials in (i) shunting systems for hydrocephalus, (ii) cortical neural prosthetics, (iii) drug delivery in the CNS, (iv) hydrogel scaffolds for CNS repair, and (v) neural stem cell encapsulation for neurotrauma. The biological and material requirements for the biomaterials in these applications are discussed. The difficulties that the biomaterials might face in each application and the possible solutions are also reviewed in this article.

Management of complicated shunt infections: a clinical report

OBJECTIVES

The authors present their experience with a protocol for the treatment of patients with complicated shunt infections.

METHODS

Complicated shunt infections are defined for the purpose of this protocol as multiple compartment hydrocephalus, multiple organism shunt infection, severe peritonitis, or infections in other sites of the body. The initial treatment protocol for these patients was 3 weeks of intravenous antibiotic therapy and 2 weeks of twice daily intraventricular/intrashunt antibiotic therapy. Cerebrospinal fluid (CSF) cultures were monitored during therapy and obtained again 48 hours after completion. The shunt was completely replaced. Additionally, follow-up cultures were obtained in all patients 3-6 months after therapy was completed.

RESULTS

A cure of the infection was achieved in all patients as defined by negative cultures obtained at completion of antibiotic therapy and in follow-up studies. The follow-up period was 2-11 years (mean 4.4 +/- 2.5 years). The treatment protocol was modified in the patients treated after 1991, and 18 patients were treated with this modified treatment regime. In these patients, intraventricular antibiotics were administered only once daily for 14 days, and the CSF was cultured 24 hours after antibiotic therapy had been stopped instead of after 48 hours. The results were similar to those obtained with the initial protocol.

CONCLUSIONS

Based on their prospective nonrandomized series, the authors believe that patients with complicated shunt infections can be successfully treated with 2 weeks of intraventricular antibiotic therapy administered once daily, concurrent with 3 weeks of intravenous antibiotic therapy. This protocol reduces length of treatment and hospital stay, and avoids recurrence of infection.

Aggressive management of shunt infection: combined intravenous and intraventricular antibiotic therapy for twelve or less days

OBJECTIVE

This report is limited to patients with a single cerebrospinal fluid (CSF) shunt infected by a single organism, and compares two treatment protocols.

METHODS

In the initial protocol (1975-1991), patients underwent removal of the shunt system and received intravenous and intraventricular antibiotics. Intraventricular antibiotics were administered twice daily to those with external ventricular drainage. When CSF was cultured 48 h off all antibiotics and found to be sterile at 24 h of incubation, a new shunt was inserted. Follow-up CSF cultures were obtained in all patients between 1-6 months following placement of the new shunt.

RESULTS

There were 25 patients (ages 1 month to 16 years; mean +/- SD: 23 +/- 4.0 months). CSF obtained from the shunt yielded the following: Staphylococcus epidermidis (19), Staphylococcus aureus (2), Streptococcus species (2), Serratia marcescens (1), and Propionebacterium species (1). The duration of intravenous antibiotics was 7-12 days (mean +/- SD: 9.7 +/- 1.3 days), and intraventricular antibiotic therapy was 6.2 +/- 1.7 days. Total hospital stay was 15.2 +/- 2.3 days. The follow-up period was 7.7 +/- 3.6 years. Following the initial protocol in another 15 patients (1992-2004), the treatment regime was modified in that intraventricular antibiotics were administered once daily in patients with external ventricular drainage, and the CSF was cultured at 24 h off antibiotics, instead of 48 h. Results were similar to the initial protocol with respect to days of antibiotic therapy and hospital stay.

CONCLUSION

Based on our retrospective nonrandomized series, we believe patients with a single shunt and noncompartmentalized hydrocephalus can be successfully treated without a prolonged antibiotic course and lengthy hospital stay.

Do antibiotic-impregnated shunts in hydrocephalus therapy reduce the risk of infection? An observational study in 258 patients

BACKGROUND

Shunt infection in hydrocephalus patients is a severe, even life-threatening complication. Antibiotic-impregnated shunts (AIS) have been developed in an attempt to reduce rate of shunt infection. The study was performed to analyze if AIS can diminish the rate of shunt infection. The pathogenic nature of shunt infection in patients with AIS systems and those without antibiotic impregnated shunts (non-AIS) was compared.

METHODS

Over a period of 24 months in the Department of Neurosurgery at University Hospital of Tübingen shunt surgery was performed in 258 patients. In 86 patients AIS systems were implanted. Shunt catheters were commercially impregnated with clindamycin and rifampicin. Analysis of the clinical data included sex, age, classification of hydrocephalus, shunt types and risk factors for shunt infection [age (< 1 year and > 80 years), prematurely born patients, external ventricular drainage, former shunt infection, former systemic infection, disturbance of consciousness, former radiation-/chemotherapy]. Infection rates and underlying bacterial pathogens of patients with AIS were compared to patients with implanted non-AIS systems (172 patients).

RESULTS

AIS and non-AIS patients did not differ in sex, etiology of hydrocephalus and the shunt type. In the AIS group 72 out of 86 patients had at least one risk factor (83.7 %), compared to 126 patients in the non-AIS group (73.3 %). There was no significant difference between the two groups (p = 0.0629; Fisher's exact test). In patients with no risk factors, only one patient with non-AIS suffered from shunt infection. In patients with one or more risk factors the rate for shunt infection was 7.14 % in patients with non-AIS and 6.94 % in patients with AIS. Former shunt infection (p = 0.0124) was related to higher risk for shunt infection. The use of AIS had therefore no significant advantage (p = 0.8611; multiple logistic regression). Significantly related to a shunt infection was the number of shunt surgeries. 190 interventions in the AIS group (2.21 interventions per patient) and 408 in the non-AIS group (2.37 interventions per patient) had been performed (p = 0.3063; Wilcoxon). There was no shunt infection in the group of patients on whom only one shunt surgery was performed. In patients with at least two shunt surgeries the infection rate was 9%. The infection rate in AIS patients was 5/52 (9.6 %) and in the non-AIS 10/114 (8.77 %), (p = 1.0; Fisher's exact test). Staphylococcus epidermidis was the most frequent pathogen for shunt infection. Fourteen out of 15 infections occurred within the first 6 months of surgery. The most frequent pathogen for shunt infection was S. epidermidis. No toxic or allergic complications were seen using the AIS shunt systems. The presented data show a remarkably low infection rate of 5.8 % in the non-AIS group compared to other studies which demonstrated a significant decrease in the infection rate by AIS.

CONCLUSION

AIS did not significantly reduce shunt infection in hydrocephalus patients in the presented study. In the AIS group three patients suffered from shunt infections caused by skin ulceration or neurosurgical procedures with exposure of the cerebrospinal liquor after shunt implantation. AIS was not developed to prevent infection in such cases, therefore an advantage of AIS can not be excluded. In view of the presented data and the small number of reported studies a prospective randomized multicenter study is required.

Nonfunctional abdominal complications of the distal catheter on the treatment of hydrocephalus: an inflammatory hypothesis? Experience with six cases

INTRODUCTION

The peritoneal cavity is the most common site of cerebrospinal fluid absorption in hydrocephalus treatment. Many distal catheter complications are the result of this type of treatment, and these have been extensively described in the neurosurgical literature.

MATERIALS AND METHODS

In our study, six cases of distal catheter migration with visceral perforation and/or extrusion are presented: three through the umbilicus, two through the scrotum, and one through the anus. An extensive review of the literature was performed.

RESULTS

The studies of peritoneal dialysis models for the treatment of chronic renal failure patients provide important data about solute absorption in the peritoneal cavity and reactivity of the peritoneal membrane.

CONCLUSION

This model, when compared to distal catheter complications on a ventriculoperitoneal (VP) shunt, presents similarities that could help understand the mechanism of the nonfunctional complications of the distal VP catheter (complication with functional shunt), providing valuable data to support an inflammatory mechanism.

Late bacterial granuloma at an intrathecal drug delivery catheter

In the case reported, neurological complaints were pain and dysaesthesiae in the lower back and thigh, as well as paresis of the ileopsoas muscle. MRI of the lumbar spine showed an intradural-extramedullary mass at the level of L1 homogeneously enhancing with gadolinium. This mass was situated at the tip of an intrathecal catheter implanted 11 years before for a morphine trial infusion as therapy for phantom pain after amputation of the right arm. Now, removal of the catheter was performed. Cultures of lumbar CSF and the catheter tip demonstrated coagulase negative staphylococcus. Antibiotic medication with cephalosporines was given for 6 weeks. After removal of the catheter, the patient was free of pain and he progressively regained full neurological function. Although most catheter-associated granulomas reported so far were sterile in nature, bacterial infection should still be considered even years after catheter placement.

Linezolid treatment of ventriculoperitoneal shunt infection without implant removal

Ventriculoperitoneal shunt infection is a serious clinical problem for which implant removal is considered the treatment of choice. However, surgery is sometimes associated with considerable risks that may outweigh the benefits. Presented here is a case of ventriculoperitoneal shunt infection treated successfully with linezolid without implant removal. This case shows linezolid could be a therapeutic alternative when surgery is contraindicated.

Hydromer-coated catheters to prevent shunt infection?

OBJECT

The authors sought to determine whether Hydromer-coated catheters (HCCs) reduce bacterial adhesion compared with plain silicone, with and without plasma conditioning; to determine whether soaking the catheter in antibiotic solution reduces catheter colonization; and to ascertain their likely efficacy in prevention of shunt infection.

METHODS

Segments of HCCs were soaked in antibiotic solutions and then tested for antimicrobial activity on serial zone plates. All antibiotic agents lost activity within 2 days, except rifampin (9 days). Bacterial adhesion (Staphylococcus epidermidis) to the external surface was measured with and without plasma protein conditioning. Chemiluminescence showed that HCCs significantly reduced adhesion, especially with protein conditioning. Bacterial challenge of the luminal surface of the HCCs under flow conditions showed no difference from plain silicone; this was also the case after soaking in high concentrations of antibiotic agents and was confirmed by scanning electron microscopy. Examination of the inner and outer surfaces of HCCs by laser confocal microscopy disclosed that the outer surface, but not the lumen, was Hydromer coated.

CONCLUSIONS

The findings of this study indicate that HCCs do not impact the major risk factors for infection; therefore, it may be inferred that HCCs cannot be expected to reduce shunt infection significantly.

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.

An investigation of structural degradation of cerebrospinal fluid shunt valves performed using scanning electron microscopy and energy-dispersive x-ray microanalysis

OBJECT

Surveys of cerebrospinal fluid (CSF) shunts that have been removed from patients have shown that even when the ventricular catheter is the cause of the obstruction, the valve may be obstructed or underperforming. The aim of this pilot study was to investigate the degradation of shunt valve structure over time due to the deposition of debris. The findings were compared with findings in unused valves.

METHODS

Scanning electron microscopy was used to visualize the structures of the valves. The items that were examined included two unused and nine explanted cylindrical medium pressure valves, one unused and six explanted Delta 1.5 valves (PS Medical, Goleta, CA), and one explanted Medos Programmable valve (Codman Johnson & Johnson, LeLocle, Switzerland). The valves were cut open, disassembled, and coated in gold. The areas that were analyzed included the main valve chamber, the diaphragm unit, and the antisiphon device. For areas with abnormal deposits, energy-dispersive x-ray microanalysis was performed to establish the chemical composition of the deposits. The reference unused valves had smooth surfaces with no deposits in any areas. All explanted valves had extensive deposits in all surveyed areas. The deposits varied from small clusters of crystals to large areas that displayed a cobblestone appearance. In diaphragm valves the deposits extensively affected the surface of the diaphragm and the gap between the diaphragm and the surrounding case, where normally CSF flows; in the Medos valve the deposits affected in the spring and "staircase" unit. Deposits were present as early as 2 weeks after implantation. On some valves there was a complete film covering the entire outlet of the valve, which formed a cast inside the valve stretching from wall to wall. The deposits consisted mostly of sodium and chloride, but occasionally contained calcium. In all infected and some noninfected valves there was a significant peak of carbon, indicating the presence of protein deposits.

CONCLUSIONS

It appears that the continuous flow of CSF through shunt valves causes surface deposits of sodium chloride and other crystals on all aspects of the valve, including the outlet pathways. The formation of deposits may be encouraged by the adhesive properties of the materials that constitute the valve parts.

Cerebral fluid edema: an unusual complication of ventriculoperitoneal shunts

INTRODUCTION

A case of accumulation of CSF into the brain parenchyma simulating a brain tumor, secondary to an obstructed ventriculoperitoneal shunt, is presented. Until now, only seven cases of this rare complication have been described.

CASE REPORT

Magnetic resonance showed an expansive, low-density intracranial lesion on the right frontal and parietal lobe. This mass was biopsied, but no tumor was found and the diagnosis was brain edema.

CONCLUSION

The mistake in the diagnosis was due to the clinical symptoms and to the MR images.

[Infections of cerebrospinal fluid shunts in the child: prevention and treatment]

Cerebrospinal fluid (CSF) shunting has developed into the mean method of treatment in children with hydrocephalus. Until the last decade, shunt infection was the most important cause of morbidity with a mean rate of 10%. Most of shunt infection (> 90%) are diagnosed within six months after surgery supporting a basic premise of direct contamination at the time of surgery. However, after applying stricter operative and perioperative protocols, some authors reported a dramatically decrease in the incidence of infectious complications. The overall annual risk of shunt infection in a paediatric neurosurgical unit is currently 1%. Risk factors are analysed with emphasis on the choice of preventive treatment. An outline of the protocol for shunt implantation is presented. There is no clearly defined role for prophylactic antibiotic medications in the prevention of shunt infection. The small sample sizes of prospective controlled clinical trials precluded sufficient statistical power. The conclusions of the meta-analyses are not sufficiently robust to resolve the controversy and it is not possible to make recommendations either for or against the use of prophylaxis in shunt surgery. The management of shunt infection is examined with emphasis on antibiotic therapy.

Percutaneous endoscopic gastrostomy in patients with ventriculoperitoneal shunts

BACKGROUND

Percutaneous endoscopic gastrostomy (PEG) may be required in neurosurgical patients with a persistently depressed neurological status or severe lower cranial nerve palsies. Such patients may have a coexisting hydrocephalus requiring cerebrospinal fluid (CSF) diversion. Despite the risk of infection resulting from exposure to oropharyngeal flora by the pull-through PEG technique and the secondary pneumoperitoneum seen in one-third of patients, simultaneous peritoneal placement of CSF shunt catheters with PEG is the current practice. The aim of the study was to determine the frequency of CSF diversionary procedures in neurosurgical patients undergoing PEG insertion and the occurrence of infective complications in patients with simultaneous placement of a PEG and a ventriculoperitoneal (VP) shunt.

METHODS

This was a retrospective review of all neurosurgical patients undergoing PEG. The presence of hydrocephalus, mode of CSF diversion and the development of subsequent infection in those having coexistent distal peritoneal catheter placement and PEG were determined.

RESULTS

PEGs were placed in 42 neurosurgical patients (9.3 per cent of all PEGs inserted), of whom 21 had a coexisting hydrocephalus. Eight of 16 shunts with distal catheter placement in the peritoneal cavity developed infection requiring revision. Infections occurred with greater frequency in patients with a tracheostomy. There were no shunt infections requiring revision in a second group of 21 patients who had a coexisting shunt and tracheostomy without PEG.

CONCLUSION

Simultaneous placement of a PEG and a VP shunt should be avoided in the acute phase of a patient's hospital admission.

Nosocomial bacterial meningitis, including central nervous system shunt infections

Nosocomial bacterial meningitis and CSF shunt infections result in considerable morbidity and mortality, necessitating an organized and thoughtful approach to prevention, diagnosis, and management. Prophylactic antibiotics appear to reduce the rate of postcraniotomy meningitis often caused by S. aureus. On the other hand, prophylactic antibiotics do not appear to reduce the risk of developing a CSF shunt infection. CSF shunt infections usually require shunt removal and antimicrobial chemotherapy to effect a successful outcome.

Biological reactions to cerebrospinal fluid shunt devices: a review of the cellular pathology

OBJECTIVE

To understand the interaction between cerebrospinal fluid shunt components and the brain and other tissues.

METHODS

A systematic review of the medical literature directly pertaining to shunt complications, and that dealing with tissues' reactions to implants in general, was conducted.

RESULTS

Vascularized pedicles of glial tissue or choroid plexus grow into ventricular catheters, primarily as a mechanical phenomenon. Cellular debris or blood can cause dysfunction of valve components. Chronic inflammation, which is nonspecific, might contribute to degradation of the components.

CONCLUSION

Care must be taken to prevent early entry of debris or blood into the shunt system. Ventricular collapse onto the shunt must be avoided. Refinement of manufacturing methods or modification of shunt materials could reduce the susceptibility of shunts to infection and improve longevity of the apparatus.

Physico-chemical properties of a rifampicin-releasing polydimethylsiloxane shunt

Infection of implanted polymeric devices is a major problem in modern medicine. Silicone shunts were modified in order to prevent microbial colonization by incorporating rifampicin. The release mechanism and the altered properties of the silicone were studied. Release rates of rifampicin out of the polymeric shunt materia were measured in vitro for up to 60 d. For high velocity of rifampicin in the polymeric matrix and long-lasting controlled release rates, high compatibility of polymer and drug was required. Compatibility and therefore miscibility of drug and polymer were estimated by reduced solubility and cohesion energy densities (Hansen parameter, solubility parameter delta). Mechanical properties of the polymer were influenced by incorporation of small drug amounts, characterized by stress-strain curves. Differential scanning calorimetry (DSC) measurements suggested thermodynamically controlled interaction of the macromolecules with the incorporated substance. The physico-chemical state of the drug in the internal phase and the surface of the polymer was studied by scanning electron micrography (SEM), showing homogeneous molecular dispersion of the drug in the polymeric material as well as crystalline structures on the surface.

Shunt malfunction in relation to shunt infection

Ventriculo-peritoneal shunt malfunction may be caused by shunt infection which may not be clinically apparent as the cause of the malfunction by standard diagnostic criteria. This suggests that the real incidence of infected shunts might be higher than previously suspected. In order to study the relationship between infection and shunt malfunction, we followed a protocol over five years (54 V-P shunts) consisting of (1) removal of the malfunctioning shunt and replacement in the same surgical procedure with a new one or institution of an external ventricular drainage for 8 days (if there were clear signs of infection), (2) culturing of CSF and every part of the removed shunt, and (3) intravenous antibiotic treatment (Vancomycin 1g./12h + Ceftriaxone 1g./12h) for five days after the new V-P shunt had been inserted. In those cases in which an external ventricular drainage had been placed, its tip and a portion of the new V-P shunt were also cultured. The results showed that although CSF cultures were negative in 49/54 cases (90.7%), cultures of the removed shunts were positive in 32/54 (59.2%), most of them (21/32, 65.6%) for Staphylococcus coagulase negative organisms. The CSF samples obtained by puncturing the reservoir on admission to Hospital were positive only in 5 out of 54 cases (9.2%), only in those showing clinical features of infection. In the remaining cases, 27 out of 54 (50%) the CSF cultures were negative but the shunt cultures proved positive and required further treatment. For the newly inserted shunts (173) CSF was collected through the shunt during the surgical procedure, and a small piece of the extra-tube from the ventricular and from the peritoneal catheter were obtained and cultured. All the six shunts (6/173, 3.4%) that showed positive cultures after insertion had to be replaced within a period of three to four weeks due to malfunction (range 26 +/- 7 days), indicating that the systematic culture of CSF and tubing helps to predict which shunts will soon need to be replaced due to infection. We conclude that CSF culture alone does not rule out infection in cases of shunt malfunction. The percutaneous CSF obtained from the shunt reservoir admission is particularly prone to show negative cultures even when the shunt is colonized by bacteria.

In-vitro efficacy of an antibiotic releasing silicone ventricle catheter to prevent shunt infection

Infection due to implanted polymeric devices is a major problem in modern medicine. Microbial colonization of implants in neurosurgery, e.g. cerebrospinal fluid (CSF) shunts is the main reason for their failure, and often results in the consequent removal of the infected implants. In this paper we report on new approaches in the prevention of bacterial infections by incorporation of an antibiotic (rifampicin) into the polymer devices (silicone). Drug release characteristics are investigated, and the physico-chemical mechanism of the delivery is discussed. Measurements of killing kinetics and the bacterial adhesion to the antibiotic-loaded silicone in a static adhesion assay reveal that only the liberation of high antibiotic doses over a period of weeks can prevent the bacterial colonization of the polymeric surface.

A concerted effort to prevent shunt infection

In an attempt to reduce the rate of shunt infection a new protocol for shunt surgery was introduced on July 1, 1988 at The Hospital for Sick Children in Toronto. The operations were done at the beginning of the day, operating room personnel were kept to a minimum, no visitors were allowed in the room, a staff neurosurgeon or neurosurgical fellow attended all operations and two doses of perioperative cloxacillin 50 mg/kg were given intravenously. From July 1, 1988 to June 30, 1989 there were 576 shunt procedures on the Neurosurgical Service and 22 (3.8%) of these resulted in a shunt infection. During the preceding year (July 1, 1987 to June 30, 1988) 581 shunt operations were performed, 75 (12.9%) of which resulted in an infection (chi 2 = 29.9, P < 0.001). It appears that the introduction of this protocol for shunt surgery has helped to reduce the risk of shunt infection from 12.9% to 3.8% (a reduction of 70.5%). The rate of infection occurring after shunt revisions was not significantly different from that occurring after new shunt insertions. When the individual factors in the protocol were analyzed, the use of antibiotics and a shorter duration of surgery appeared to be related to a lower shunt infection rate.

Shunt implantation: reducing the incidence of shunt infection

Shunt infection remains the foremost problem of shunt implantation after mechanical malfunctions. Diversionary cerebrospinal fluid shunt implantation has a high complication rate, with 5% to 15% of such shunts becoming infected. Of these infections, 70% are diagnosed within 1 month after surgery and more than 90% within 6 months. Shunt infection in the vast majority of cases is therefore a complication of shunt surgery. The authors review their experience with shunt implantation during two time periods. From January, 1978, to December, 1982, 302 children with hydrocephalus underwent 606 operations. Among these children, 47 (15.56%) developed a proven shunt infection, with an incidence of infection per procedure of 7.75%. As a result of this study, a new protocol for shunt procedures involving modifications in the immediate pre-, intra-, and postoperative management of children undergoing shunt implantation was initiated. With this new protocol, 600 children underwent a total of 1197 procedures between January, 1983, and December, 1990. The incidence of shunt infection decreased dramatically, with two infections (0.33%) in 600 patients and a per-procedure rate of 0.17%. The overall annual risk of a shunt infection in the pediatric neurosurgical unit is currently 1.04%.

Forces involved in adhesion of Bacillus cereus spores to solid surfaces under different environmental conditions

The adhesion of Bacillus cereus spores (NCTC 2599) to hydrophobic and hydrophilic glass surfaces was studied when environmental conditions were varied. The spores were exposed in media of different polarities as well as different pH and ionic concentrations. With increasing ethanol concentrations, the polarity of the medium was decreased and the predominant force of attraction was found to be hydrophobic. The spore surface was uncharged at a pH around 3, at which value the spore was most adhesive to both hydrophobic and hydrophilic glass. This could be attributable to the absence of electrostatic repulsion. An increased ionic concentration of the bulk increased the degree of adhesion especially to the hydrophilic surfaces. This indicates the suppression of a solvation barrier at high ionic concentrations, when the polymers of the spore surface become dehydrated.