In vitro and in vivo efficacy of a rifampin-loaded silicone catheter for the prevention of CSF shunt infections

Summary Infection of cerebrospinal fluid (CSF) shunts is one of the major complications associated with their use and is usually managed by shunt removal, temporary insertion of an external drainage and implantation of a new shunt system. We have evaluated the efficacy of a rifampin-loaded silicone ventricular catheter to prevent bacterial colonization and infection in vitro and in an animal model.On the basis of an incorporation process a rifampin-loaded catheter was developed which is capable of releasing rifampin in bacteriocidal concentrations for 60 days and more. In a stationary bacterial adherence assay usingS. epidermidis as test strain, the colonization resistance of the device was demonstrated.To assess the capability of the catheter to prevent CSF shunt infections, a rabbit model was developed which allowed the establishment of a reliable and reproducible CSF infection by implantation of silicone catheters into the ventricle and inoculatingS. epidermidis (minimal dose 10⁶ cfu) orS. aureus (minimal dose 10³ cfu). Rifampinloaded catheters (12 animals inoculated with S. epidermidis, 8 animals inoculated with S. aureus) were compared with non-loaded (14 animals inoculated with S. epidermidis, 19 animals inoculated with S. aureus) control catheters, and infection was documented by clinical, microbiological and histological methods.In contrast to the control group, none of the animals with rifampin-loaded catheters showed clinical signs of infection. Furthermore, in none of the materials obtained after sacrifice of the animals (catheter, brain tissue, CSF, blood) could the infecting bacteria be cultured, whereas in materials from animals with the unloaded catheter the infecting strains could always be cultured from the catheter and from surrounding brain tissue. The histological examination of catheter-adjacent tissue supported these findings.We conclude that a rifampin-loaded silicone ventricular catheter is capable of completely preventing bacterial colonization and infection by staphylococci as the main causative organisms in CSF shunt infections and should be further evaluated in clinical trials.     

Effect of hydrophilic coating on microorganism colonization in silicone tubing

Summary Background. Shunt infections are one of the major causes of mortality and morbidity of patients with hydrocephalus. The aim of this research is to compare the bacterial colonization characteristics of a regular silicone elastomer shunt material coated with polyvinylpyrrolidone and dimethylpolysiloxane (silicone).Method. Regular coated shunt materials were compared by in-vivo and in-vitro methods. In the in-vitro experiment, silicone and coated material immersed and not immersed in vancomycin solution was treated with a certain concentration of Staphylococcus epidermidis. In the in-vivo study, silicone and coated material specimens were treated with Staphylococcus epidermidis and they were stereotactically placed in the lateral ventricles of the rats. One week after the inoculation, shunt pieces were removed and the colonies were counted by using a scanning electron microscope.Findings. There was a statistically significant difference of colonization in the in-vitro groups in coated material vs. silicone, coated material vs. vancomycin treated silicone, vancomycin treated coated material vs. silicone, vancomycin treated coated material vs. vancomycin treated silicone. There was no statistically significant difference for colonization in in-vitro groups of coated material and vancomycin treated coated material. With in-vivo experiments we can say that, coated material catheters are superior than the silicone catheters in respect to colonization but after the bacterial colonization has occurred, the amount of colonization did not differ.Interpretation. Coated material catheters are superior to silicone catheters and they prevent bacterial colonization in some respect.     

In vitro activity of daptomycin and vancomycin lock solutions on staphylococcal biofilms in a central venous catheter model.

BACKGROUND: Catheter lock solutions are used for prevention and management of catheter-related bloodstream infections. We investigated the activity of daptomycin and vancomycin lock solutions against Staphylococcus aureus and Staphylococcus epidermidis in an in vitro central venous catheter (CVC) model. METHODS: Biofilm-producing reference strains of S. aureus and S. epidermidis were evaluated. After 24 h of bacterial growth in a CVC model, daptomycin and vancomycin bactericidal activity (+/- preservative-containing heparin sodium) were separately evaluated as a lock solution using 0.5, 1 and 35 mg/ml. Calcium carbonate (50 mg/l) was added to all lock solutions containing daptomycin. Each CVC was drained, flushed and sonicated at 72 h to assess CFU/ml. RESULTS: After 72 h of exposure in the catheter lock solutions, daptomycin and vancomycin at 0.5, 1 and 5 mg/ml demonstrated bactericidal activity (>3.0 log10 CFU/ml) against S. aureus and S. epidermidis (P 相似文献   

Use of elemental iodine for shunt infection prophylaxis

OBJECTIVE: Elemental iodine (I(2)) can kill a broad spectrum of organisms, including bacteria, fungi, and viruses. Furthermore, it is inexpensive, bacterial resistance is unknown, and allergic reactions are rare. Because of these properties, we wanted to determine the concentration of I(2) that would kill Staphylococcus epidermidis and Staphylococcus aureus without causing injury to the central nervous system, in an attempt to further reduce the rates of shunt infections. METHODS: Bacterial kill studies using S. epidermidis and S. aureus were performed by using Ringer's lactate solution alone or solution containing I(2) at a concentration of 5, 10, 20, 50, 100, or 1000 parts per million (ppm), cefazolin at 1 mg/ml, or bacitracin at 100 units/ml. Twenty-one adult male Wistar rats, in seven groups, underwent a frontoparietal craniectomy. The surfaces of their brains were irrigated for 1 hour with Ringer's lactate solution alone or solution containing I(2) (at the concentrations noted above). After 72 hours of observation, the animals were killed. Their brains were then fixed in formalin, stained with hematoxylin/eosin, and examined. RESULTS: Even with exposure of only 15 seconds to an I(2) solution of 20 ppm, no growth was detected with an inoculum of either bacteria of 100 million. In contrast, the two antibiotics were not nearly as effective as I(2), with kill rates ranging from 19 to 93%. Examination of the rat brains demonstrated no histological changes after subarachnoid exposure to solutions containing 5, 10, 20, or 50 ppm; however, necrosis was observed with concentrations of 100 and 1000 ppm. CONCLUSION: I(2) can be added to irrigation solutions in sufficient concentrations to be bactericidal without causing any central nervous system injury.     

Ventriculoperitoneal shunt infections in children. A 6-year study

In a study of ventriculoperitoneal shunt infections conducted retrospectively between 1983 and 1987 and prospectively in 1988 39 infections from 372 shunt procedures (incidence 10.5%) were identified. The most common organism isolated was Staphylococcus aureus (18; 47%) followed by S. epidermidis (10; 26%). Forty-two per cent of staphylococci were methicillin-resistant. Gram-negative infections were associated with myelomeningoceles and Gram-positive infections with other forms of hydrocephalus (P = 0.048). Lymphocyte predominance was found more frequently than polymorphonuclear predominance in cerebrospinal fluid.     

Origin of organisms infecting ventricular shunts

Results of skin cultures obtained before 413 of 505 operations for cerebrospinal fluid-diverting ventricular shunt placement or revision in a pediatric population from April 1980 to May 1983 are analyzed and compared to results of cultures from 20 subsequent shunt infections. Sensitivities to 11 different antibiotics were determined for each isolate cultured. The total operative infection rate was 20 of 505 (4%). Gram-negative bacilli alone accounted for 3 of 20 (15%) shunt infections. One gram-negative bacillus/Staphylococcus aureus infection occurred. Factors predisposing for gram-negative bacillus shunt infection were found in all 4 cases. The majority of shunt infections were caused by typical resident skin organisms: Staphylococcus epidermidis alone, 9/20 (45%); Staphylococcus aureus alone, 4/20 (20%); Corynebacterium sp., 1/20 (5%); alpha-Streptococcus with S. epidermidis, 1/20 (5%); and Micrococcus with S. epidermidis, 1/20 (5%). Only 4 (20%) of the 20 shunt infections were due to organisms identical to those originally grown from the skin. Another 4 (20%) seemed to be infected with a strain of organism different from that initially recovered from the skin. The remaining skin organism shunt infections may or may not have come from the patient's skin. The data suggest that not all skin organism shunt infections arise from contamination by resident skin bacteria at the incision sites at the time of operation. Alternate sources for the infecting organisms are discussed. The antibiotic sensitivity data on skin isolates and shunt isolates suggest that vancomycin is the antibiotic best suited for prophylaxis against shunt infection at our institution.     

Bacterial Skin Contamination Before and After Surgical Preparation of the Foot,Ankle, and Lower Leg in Patients with Diabetes and Intact Skin versus Patients with Diabetes and Ulceration: A Prospective Controlled Therapeutic Study

Eradication of bacterial flora from the foot, especially the nailfolds and toe webspaces, through surgical preparation remains a challenge. All previous studies have involved healthy patients undergoing elective foot and ankle surgery or healthy volunteers. However, the patient with diabetes is considered an immunocompromised host with decreased ability to combat invasive bacterial infections. The use of an efficacious surgical preparation is therefore of paramount importance. The author conducted a prospective study involving patients with diabetes with and without ulceration who underwent the current “best evidence available” surgical preparation (i.e., chlorhexidine gluconate [4%] scrub followed by alcohol impregnated with iodine [1%] solution). Qualitative aerobic cultures before and after completion of this surgical preparation technique were obtained from the hallux nailfold; second, third, and fourth toe webspaces (as one culture); and distal anterior tibia. A total of 120 organisms were cultured before surgical preparation with 64 in the elective group and 56 in the ulcerated group. The most commonly isolated organism was methicillin-resistant Staphylococcus epidermidis, which was identified in 46 pre-preparation cultures (38.3%). This was followed by methicillin-sensitive S. epidermidis (16.7%) and “other” organisms (10.0%). There was a significant reduction for both numbers of organisms identified and positive cultures for the 3 most commonly isolated organisms after surgical preparation. Based on the results of this study, the surgical preparation used here appears to be an efficacious surgical preparation technique for eradicating aerobic bacterial pathogens from the foot in patients with diabetes both with and without ulceration. The high incidence of methicillin-sensitive and methicillin-resistant S. epidermidis found in this patient population is a cause for concern, especially when metallic fixation is intended to be implanted.     

Infection-resistant continuous peritoneal dialysis catheters

The techniques of bonding of anionic antibiotics by treatment with cationic surfactants were applied to continuous ambulatory peritoneal dialysis (CAPD) catheters. The elution of 14C-penicillin from tridodecylmethylammonium chloride (TDMAC) treated silicone elastomer catheters in dialysis solution was biphasic, with 95% dissociated from the catheter by 48 h. Forty percent of the TDMAC left the catheter surface during the initial 2 days. The ability of the surfactant TDMAC to bind antibiotics after incubation in dialysis solution correlated directly with the amount of surfactant remaining. Rats with intraperitoneal dialysis catheters were inoculated with exit site and intraluminal bacterial challenges. Intraperitoneal catheter tips treated with TDMAC-penicillin were rendered more resistant to colonization after exit site and intraluminal bacterial challenges.     

Response of chronic renal failure mice to peritoneal Staphylococcus epidermidis challenge: impact of repeated peritoneal instillation of dialysis solution

The effect of repeated instillation of peritoneal dialysis (PD) solution on the peritoneal clearance of a Staphylococcus epidermidis challenge was investigated in a mouse model of surgically induced chronic renal failure. For periods of up to 2 weeks, mice bearing peritoneal catheter implants underwent daily (3 mL) or twice daily (1.5 mL) peritoneal instillation of PD solution (4.25% dextrose) by transcutaneous injection into the catheter lumen. Peritoneal instillation of PD solution did not have a significant influence on the microbiological status of peritoneal structures of renal failure or sham-operated mice following experimental intracatheter S epidermidis inoculation with 10(6) colony-forming units (CFU) (assessment 48 hours after inoculation) or 10(8) CFU (assessment 1 week after inoculation). Microbiological and scanning electron microscopy (SEM) assessments of recovered peritoneal catheters demonstrated that S epidermidis remained associated with the catheter site after other peritoneal structures had become culture negative. SEM of the parietal peritoneum revealed striking morphologic alterations of the mesothelial surface as a consequence of daily PD solution infusion. In the absence of S epidermidis inoculation, repeated instillation of PD solution caused a marked acute peritoneal inflammation without evidence of a concomitant systemic inflammatory response. Furthermore, peritoneal inflammatory response to S epidermidis challenge was augmented by the infusion procedure. Concurrent assessments of inflammatory response and microbiological status revealed that, in spite of heightened peritoneal inflammatory response with peritoneal infusion, bacterial clearance from the catheter site was not improved. Although the animal preparation was limited to peritoneal infusion without drainage, the influence of repeated peritoneal instillation of hyperosmolar, acidic PD solution on the response of mice to S epidermidis challenge was successfully addressed.     

An in vitro study of the properties influencing Staphylococcus epidermidis adhesion to prosthetic vascular graft materials.

This study examines the influence of the properties of various vascular graft materials on the bacterial adherence process of two different strains of Staphylococcus epidermidis (mucous and normucous producing). Dacron grafts (both knitted and woven), Teflon grafts, and Dacron grafts coated with one and two layers of silicone were studied because these materials differ significantly in porosity, hydrophobicity, and surface charge (zeta potential). Graft segments were immersed in 3H-labeled bacteria solution for periods ranging from 5 to 180 minutes and liquid scintillation techniques were used to quantify bacterial adherence. The porous knitted Dacron material had a significantly higher rate of bacterial adherence than either the woven Dacron or Teflon (p less than 0.05). Silicone coating (either one or two layers) reduced adherence by a factor of four for the knitted Dacron (p less than 0.05) and by a factor of two for woven Dacron (p less than 0.05). The mucous producing strain of S. epidermidis displayed significantly better adherence to woven and knitted Dacron than the normucous producing strain, but only when 0.25% dextrose was added to the bacteria solution. These findings indicate that the highly porous knitted Dacron grafts have the highest propensity for bacterial adhesion. Graft materials with the most negative zeta potentials are more resistant to bacterial adherence. Silicone coating of Dacron material significantly changed adherence characteristics, suggesting that this may be a viable strategy for protecting implantable medical devices containing materials to which bacteria readily adhere.     

Treatment of catheter-related bacteraemia with an antibiotic lock protocol: effect of bacterial pathogen.

BACKGROUND: The standard therapy of dialysis catheter-related bacteraemia involves both systemic antibiotics and catheter replacement. We reported recently that instillation of an antibiotic lock (highly concentrated antibiotic solution) into the catheter lumen after dialysis sessions, in conjunction with systemic antibiotics, can successfully treat many episodes of catheter-related bacteraemia without requiring catheter removal. The present study evaluated whether the likelihood of achieving a cure with this protocol depends on the type of pathogen. METHODS: This was a historically controlled interventional study of an antibiotic lock protocol for the treatment of catheter-related bacteraemia. We analysed prospectively the likelihood of clinical cure (fever resolution and negative surveillance cultures) with an antibiotic lock protocol among patients with dialysis catheter-related bacteraemia. In addition, infection-free catheter survival was evaluated for up to 150 days, and compared with that observed among patients managed with routine catheter replacement. RESULTS: Overall, the antibiotic lock protocol was successful in 33 of 47 infected patients (70%) with catheter-related bacteraemia. The likelihood of a clinical cure was 87% for Gram-negative infections, 75% for Staphylococcus epidermidis infections, and only 40% for Staphylococcus aureus infections (P = 0.04). The median infection-free catheter survival with the antibiotic lock protocol was longer than that observed among patients with routine catheter replacement (154 vs 71 days, P = 0.02). CONCLUSIONS: The clinical success of an antibiotic lock protocol in eradicating catheter-related bacteraemia while salvaging the catheter is highly dependent on the bacterial pathogen. Thus, the overall success rate in an individual dialysis programme will depend on the relative frequencies of different bacterial pathogens.     

The effect of the Y-set on catheter infection rates in continuous ambulatory peritoneal dialysis patients

We hypothesized that catheter infections in continuous ambulatory peritoneal dialysis (CAPD) patients may be reduced with a disconnect system. We examined this theory in 116 CAPD patients over a 2-year period. In CAPD patients who switched to the Y-set (n = 22), the catheter infection rate decreased from one per 13 patient-months to one per 26 patient-months (P = 0.05), whereas the catheter infection rate in matched controls (n = 22) remained unchanged. Patients who began CAPD using the Y-set (n = 36) had catheter infection rates of one per 14 patient-months versus one per 8 patient-months in matched controls (n = 36, P = 0.05). Staphylococcus aureus was the most common cause of catheter infections in both groups of patients. However, Pseudomonas aeruginosa replaced Staphylococcus epidermidis as the second most common cause of catheter infections in the patients using the Y-set. The number of catheters that had to be removed due to catheter infections, mainly those due to S aureus or P aeruginosa, was the same in the Y-set and control groups. We conclude that the Y-set system is associated with reduced numbers of catheter infections, but that catheter loss from catheter infections remains a serious problem.     

Pharmacokinetics of a new skin wound cleanser

Iodophors are effective germicidal agents that have prolonged antiseptic activity in contaminated wounds. A nontoxic surfactant, Pluronic F-68, has been used to formulate a safe and effective iodophor. The parameters necessary to regulate the activity of the iodophor were studied to develop a potent, yet safe bactericidal solution for use in human subjects.The parameters found to be most important were the pH of the solution and the concentration of sodium iodide. Lowering the pH of iodophors increased their stability and antiseptic activity. The free iodine in iodophor solutions prepared with a low pH is predominantly the highly biocidal diatomic iodine (I₂). The concentration of iodide regulated the equilibrium of the dissolved iodine between its free and complexed form. Increasing the concentration of iodide in the iodophor lowered the amount of free iodine in solution and enhanced the concentration of the complexed iodide. It is the level of free iodine in an iodophor that determines its antiseptic activity. Low levels of free iodine yielded iodophors that had a slow bacterial kill rate but a prolonged duration of action. Manipulation of these variables permitted the generation of iodophors that varied considerably in their kill rates of bacteria and their duration of antibacterial activity. Iodophors tested in this study demonstrated a distinct superiority to noncomplexed iodine solutions (tincture and aqueous iodine solutions) as wound and skin cleansers.     

Adherence of Staphylococcus aureus isolated in peritoneal dialysis-related exit-site infections to HEp-2 cells and silicone peritoneal catheter materials

Background. Peritoneal catheter exit-site infections cause a relevant morbidity in peritoneal dialysis patients and are frequently caused by Staphylococcus aureus. We tested the hypothesis that adherence of exit-site-derived S.aureus to epithelial cells and peritoneal catheter silicone tubes discriminates virulent and less virulent strains. Methods. The binding of isolated S. aureus to an epithelial cell line (HEp-2) and to silicone tubes was analyzed using light-microscopy or radioactive labeling of bacteria. Results. Of 378 exit-site swabs, 99% (26%) were positive for microbial growth. S. aureus was cultured in 25 of 99 positive swabs; three of 13 swabs taken in exit-site infections grade 3 and 4 that had tested positive for S. aureus. Adherence of S. aureus from exit-site infections grade 2, 3 and 4 to Hep-2 cells did not differ from adherence of bacteria isolated from asymptomatic or moderately inflamed catheter exit sites (grade 0-2). However, binding of S. aureus to silicone tubes was enhanced in grade 0/1 compared with grade 2-4 exit-site isolates. Conclusions. Staphylococcus aureus is an important pathogen in CAPD-related exit-site infection being isolated in about 6.6% of all exit-site swabs (and in 25% of all positive swabs). Silicone-adhesive strains may be of more clinical significance in peritoneal dialysis patients since adhesion to silicone was increased in S. aureus strains isolated in more severe exit-site infections.     

Shur-clens: an agent to remove silicone gel after breast implant rupture

Removal of silicone gel from surrounding tissues after implant rupture is difficult. Local inflammation, infection, and silicone granulomas warrant thorough removal of the silicone gel. Shur-Clens (20% solution of the surfactant poloxamer 188), povidone-iodine, and saline are agents that are used to aid in the removal of silicone gel from tissue. The purpose of this study was to compare the efficacy of silicone gel removal by these three agents in vitro. Shur-Clens, povidone-iodine, and saline were compared as solvents for silicone gel. Four weight increments of silicone gel (0.02 g, 0.04 g, 0.06 g, and 0.08 g) were placed on glass slides. These slides were placed in separate beakers containing 40 ml test solution. The slides were soaked for 1 minute with gentle agitation. The slides were removed, rinsed gently with de-ionized water, and placed in a vacuum desiccator to dry. The slides were weighed to determine the amount of silicone removed after soaking in the solution. Analysis of variance was used to determine the significance between the three solvents. The percentages of silicone gel removed for the four weight increments (0.02 g, 0.04 g, 0.06 g, and 0.08 g) in saline were 5.6%, 2.9%, 2.1%, and 5.8%, respectively. In povidone-iodine solution, the percentages were 18.9%, 25.4%, 28.8%, and 51.9%. In Shur-Clens, the percentages were 31.3%, 43.0%, 63.5%, and 79.9%. The greater percentage of silicone gel removed by Shur-Clens was significant compared with the other solutions (p < or = 0.05). Shur-Clens was shown to be a more effective solvent for removal of silicone gel in vitro. This enhanced efficacy is a result of the fact that Shur-Clens contains 20% of the surfactant poloxamer 188. The authors' clinical experience with 7 patients who underwent ruptured silicone breast implant removal demonstrated the superiority of Shur-Clens. Shur-Clens is a surfactant cleanser that is widely available, is inexpensive, and has a good safety profile. They propose the use of Shur-Clens to clean silicone gel spillage to decrease local complications resulting from residual silicone gel.     

Long-term analysis of cerebrospinal fluid shunt infections. A 25-year experience.

The authors have retrospectively analyzed 840 cerebrospinal fluid shunting procedures over a 25-year period to determine the relationships between infection rates and several possible influences on infection. Two-thirds of all shunt infections occurred within 1 month of surgery. The very young and very old had higher infection rates. Infections became less prevalent over the period of the study, and mortality from infection decreased from 35% to 6%. Successive shunts (revisions) were found to have progressively higher infection rates. Ventriculoatrial and ventriculoperitoneal silicone plastic shunts had similar infection rates (11.4% and 12.0%). The uncontrolled use of prophylactic antibiotics had no effect on shunt infections. Staphylococcus epidermidis became gradually more prevalent over the period of the study, and eventually caused one-half of all infections. Where infection occurred in the presence of prophylaxis, the infectious organism was usually sensitive to the antibiotic being used. The surgeon was found to be the largest single factor in the incidence of shunt infections. A 25-fold variance in infection rates among surgeons could be related to individual experience and technique.     

Factors causing acute shunt infection. Computer analysis of 1174 operations

A series of 1174 operations performed on 802 hydrocephalic children was analyzed in an effort to find the factors causing acute postoperative infection. Culture of the cerebrospinal fluid (CSF) samples during the operation was positive in 33 cases. These cases were excluded from the series. Ninety infections were observed in the remaining 1141 operations, an overall rate of 7.9%. Most of these infections were meningitis (56 cases). Staphylococcus epidermidis was the bacterium most frequent identified (44%). Statistically significant relationships were found between shunt infection and the following factors: 1) age: infection was 2.6 times as frequent before 6 months than after 1 year of age (p = 0.03); 2) poor condition of the skin; 3) presence of intercurrent seats of infection at the time of surgery; 4) type of operation: the rate of infection was 8.4% in primary shunt insertions, 5% in shunt revisions, and 17.5% in reinsertions following shunt removal for infection (p = 0.0001); 5) end of the shunt requiring revision: an infection rate of 7.7% followed revision of the ventricular catheter alone, and 2.6% followed revision of the other end alone (p = 0.012); and 6) postoperative wound dehiscence or scalp necrosis. The surgical team involved was poorly correlated with the rate of infection (p = 0.12). No statistically significant relationships have been found between infection and 1) etiology of hydrocephalus: 2) sex; 3) recent neurosurgical operation before the shunt procedure; 4) preoperative presence of an external drainage tube or CSF fistula; 5) lumbar or ventricular taps, or ventriculography; 6) number of previous operations performed on the shunt; 7) time (month and year) of operation; or 8) sugar level and cell count in the CSF.     

Clinical management of dialysis catheter-related bacteremia with concurrent exit-site infection

Dialysis catheter-related bacteremia (CRB) can frequently be treated with systemic antibiotics, in conjunction with an antibiotic lock, in an attempt to salvage the catheter. It is unknown whether CRB associated with an exit-site infection can be treated with such an approach. We retrospectively queried a prospective, computerized vascular access database, and identified 1436 episodes of CRB, of which 64 cases had a concurrent exit site. The frequency of concurrent exit-site infection was 9.6% with Staphylococcus epidermidis, 6.1% with Staphylococcus aureus, and only 0.7% with Gram negative CRB (p < 0.001 for Staphylococcus vs. Gram negative rods). Five serious complications (four major sepses and one endocarditis) occurred in 24 patients with S. aureus infection, but none in 32 episodes of S. epidermidis infection (p = 0.01). Catheter survival was significantly shorter in patients with S. aureus infections. The median catheter survival (without infection or dysfunction) was 14 days with S. aureus vs. 30 days with S. epidermidis infection (p = 0.035). In conclusion, concurrent exit-site infection is seen most commonly in association with Staphylococcal CRB. When the infecting organism is S. epidermidis, attempted salvage with systemic antibiotics and an antibiotic lock is reasonable. However, prompt catheter removal is indicated when the pathogen is S. aureus.     

Role of an intraperitoneal catheter implant in the pathogenesis of experimental Staphylococcus epidermidis peritoneal infection in renal failure mice

The influence of a permanent peritoneal catheter implant on the response of renal failure and control mice to peritoneal inoculation with 10(6) colony-forming units (CFU) Staphylococcus epidermidis was assessed 48 h after bacterial challenge. Two weeks after the surgical induction of renal failure or sham surgery, a segment of a peritoneal dialysis catheter was implanted entirely within the confines of the peritoneal cavity of mice. One month later peritoneal S. epidermidis inoculation was performed by transcutaneous injection through the abdominal wall either directly into the peritoneal cavity (i.p.) or via the catheter lumen (i.c.). Following i.p. inoculation, minimal bacterial growth was recovered from the peritoneal structures of all mice, including the peritoneal catheter. In contrast, following i.c. S. epidermidis challenge, the catheter site remained heavily colonized while peritoneal washings and parietal peritoneum again presented minimal bacterial recoveries. S. epidermidis recovery from the catheter site of renal failure mice was significantly greater than from the respective site of sham-operated controls. Scanning electron microscopy of catheter segments recovered from mice following i.c. inoculation revealed single cocci or microcolonies associated with the catheter surface and differential leukocyte counts of fluid aspirated from the catheter lumen revealed evidence of acute inflammation. Signs of inflammatory processes in peritoneal washings and peripheral blood, however, were not observed. These results are discussed in relation to S. epidermidis peritonitis and continuous ambulatory peritoneal dialysis.     

A prospective evaluation of blood culture versus standard plate techniques for diagnosing peritonitis in continuous ambulatory peritoneal dialysis

Peritonitis remains a major cause of morbidity in patients treated with continuous ambulatory peritoneal dialysis (CAPD). Culture-negative episodes of peritonitis occur at rates of up to 20%, and in part may reflect inadequate culturing techniques of peritoneal effluent. Through a large, prospective study, the improved sensitivity of a blood culture system, when compared with a standard plate technique (P = 0.001), for the detection of bacterial growth in 67 episodes of CAPD peritonitis is demonstrated. Improved recognition of infections caused by gram-positive organisms, primarily Staphylococcus epidermidis, was especially significant using the blood culture system (P = 0.0001). Because of improved sensitivity and a decreased time to organism identification, particularly with infections caused by S epidermidis, the most common cause of bacterial peritonitis in CAPD patients, we suggest that a blood culture system be the standard means of culturing peritoneal fluid in CAPD patients with peritonitis. The lysis-centrifugation system of culturing peritoneal fluid is also discussed in comparison with the blood culture system.