Antibacterial activity of antibiotic coated silicone grafts

PURPOSE: Postoperative infection remains one of the most serious complications of implantation of penile prostheses. Attempts to reduce the rate of infection by spraying the prosthesis with an antibiotic solution prior to implantation, along with perioperative antibiotics, have failed to eradicate infection. No published studies have evaluated the effect of antibiotic coating of penile prostheses. In this study, we evaluate the antibacterial effect of antibiotic-coated silicone strips as a surrogate for the penile prosthesis. MATERIALS AND METHODS: Strips coated with several different antibiotics were dipped in bacterial solutions containing Staphylococcus epidermidis or S. aureus and implanted subcutaneously in adult Sprague-Dawley rats. After a week, the strips were removed, and the number of bacteria on the strips and in the surrounding tissue were determined. The in vitro antibiotic activity of the antibiotic-coated strips against the same organisms was also determined. RESULTS: In the group of rats that received silicone strips contaminated in vitro with S. epidermidis, six of nine control rats yielded strips and tissues containing heavy bacterial growth. None of six strips coated with rifampin/minocycline yielded bacterial growth, nor did any of the seven strips coated with vancomycin. One of seven rats that received amikacin-coated strips had infection of the strip. The tissue results were similar to the strip results. In the group using S. aureus as the contaminating bacterium, the strips and tissues from eight of nine control rats yielded bacteria. None of the six rifampin/minocycline-coated strips yielded bacteria, while two of seven vancomycin-treated strips and two of six amikacin-coated strips were infected with S. aureus. The difference in bacterial growth between controls and antibiotic-coated strips reached a level of statistical significance for the rifampin/minocycline and vancomycin groups and was highly significant for the rifampin/minocycline groups. CONCLUSION: The experimental results presented here suggest that coating silicone graft material with antibiotics, particularly rifampin/minocycline, can reduce the incidence of graft colonization in contaminated wounds in rats, even in the absence of systemic antibiotics. These graft materials may prove useful in preventing the infection of penile prostheses.     

Effects of syntactic structure and propositional number on patterns of regional cerebral blood flow

BACKGROUND: Intravascular catheters are associated with severe infections in patients, but only few reports on this problem in animal research exist. OBJECTIVE: We report on catheter-related bacterial colonization and its consequences in long-term catheterized animals. MATERIAL AND METHOD: Foxhounds were instrumented with intravascular catheters and flow probes to study the regulation of renal blood flow and pressures. RESULTS: After flushing the catheters, alterations in renal blood flow were observed and these could be related to bacterial colonization of intravascular catheters with Pseudomonas species. After attention had been focused on aseptic technique in all experimental phases and prophylactic antibiotic lock instituted, the occurrence of Pseudomonas bacteremia ceased, and the magnitude and incidence of catheter-related colonization and infection by Pseudomonas species dropped considerably. CONCLUSION: The catheter-related colonization that occurred spontaneously in these animals resembled findings in animal experiments in which catheter-related infections were deliberately induced as well as observations made with regard to catheter-related infections in patients. This report emphasizes the importance of asepsis when working with animals with long-term intravascular catheters. We suggest that monitoring for this complication, e.g., by means of catheter cultures at the time of removal, should routinely be part of protocols for animal experiments using long-term intravascular catheters.     

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.     

Blood pressure reactivity in the evaluation of resting blood pressure and mood responses to pindolol and propranolol in hypertensive patients

Bacterial adherence on to several materials with a potential application in reconstructive surgery was studied. Polymer (poly(L-lactide)), composite (hydroxyapatite/poly(L-lactide)) and metal (316L stainless steel) were evaluated both as smooth and sandblasted specimens. All materials were incubated in phosphate-buffered saline, challenged with Staphylococcus aureus or S. epidermidis and evaluated for up to 24 h. S. aureus showed a preference for the metal and composite tested over the polymer used. For S. epidermidis no preference was found for one of the investigated materials. The influence of surface roughness on bacterial growth was demonstrated by increased colonization on the sandblasted specimens.     

Control of shunt infection. Report of 150 consecutive cases

The author analyzes 150 consecutive ventriculovenous, ventriculoperitoneal, and lumboperitoneal shunt procedures with particular attention to shunt colonization by Staphylococcus epidermidis. There was one primary infection with Staphylococcus epidermidis early in the series, and in two other cases, the organism was felt to be a secondary invader. In those procedures involving either primary placement or revision of a ventriculovenous shunt, there was not a single infection. The operative protocol that has virtually eliminated Staphylococcus epidermidis is outlined.     

Use of liposome-immunopotentiated exopolysaccharide as a component of an ovine mastitis staphylococcal vaccine

Experiments on the development of a vaccine against staphylococcal mastitis were carried out in ewes. The vaccine (Spanish patent no. 9200223) has the following components: (i) inactivated (formalinized) bacteria (Staphylococcus aureus and a coagulase-negative staphylococcal species. Staphylococcus simulans) and S. aureus toxoid in presence of an adjuvant (dextran sulfate, Mw 500,000); and (ii) S. aureus exopolysaccharide included within liposomes. High serum antibody titres were obtained against whole cells from Staphylococcus aureus, Staphylococcus simulans, Staphylococcus hyicus and Staphylococcus epidermidis strains. However, there was no response to cells from Staphylococcus warneri and Staphylococcus chromogenes strains. An immune response (serum IgG) against the inoculated exopolysaccharide was obtained when > or = 20 micrograms of exopolysaccharide were included in liposomes and when > or = 20 mg of exopolysaccharide were adjuvanted with dextran sulfate instead of liposomes. For experimental infection assays, ewes were vaccinated during pregnancy and challenged either with a low virulence S. simulans strain or with a highly virulent S. aureus strain. In these assays, the incidence of S. simulans subclinical mastitis and of S. aureus acute mastitis was significantly lower in vaccinated animals than in unvaccinated controls. Specifically, on challenge with S. simulans, two out of 14 glands became infected among the vaccinated animals and nine out of ten glands in the unvaccinated group (p < 0.001). On challenge with S. aureus, no protection was detected when component (ii) was omitted from the vaccine; nine out of ten animals developed mastitis (two mild, two moderate and five severe).(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibitory mechanisms of glycoprotein fraction derived from Miscanthus sinensis for the immediate phase response of an IgE-mediated cutaneous reaction

OBJECTIVE: To determine the risk factors for colonization or infection with methicillin-resistant Staphylococcus aureus in human immunodeficiency virus (HIV)-infected patients. DESIGN: Retrospective matched-pair case-control study. SETTING: Continuity clinic and inpatient HIV service of a university medical center. POPULATION: Patients with HIV infection from the general population of eastern and coastal Texas and from the Texas Department of Criminal Justice. DATA COLLECTION: Patient charts and the AIDS Care and Clinical Research Program Database were reviewed for the following: age, race, number of admissions, total hospital days, presence of a central venous catheter, serum albumin, total white blood cell count and absolute neutrophil count, invasive or surgical procedures, any cultures positive for S. aureus, and a history of opportunistic illnesses, diabetes, or dermatologic diagnoses. Data also were collected on the administration of antibiotics, antiretroviral therapy, steroids, cancer chemotherapy, and subcutaneous medications. RESULTS: In the univariate analysis, the presence of a central venous catheter, an underlying dermatologic disease, lower serum albumin, prior steroid therapy, and prior antibiotic therapy, particularly antistaphylococcal therapy or multiple courses of antibiotics, were associated with increased risk for colonization or infection with methicillin-resistant S. aureus. Multivariate analysis yielded a model that included presence of a central venous catheter, underlying dermatologic disease, broad-spectrum antibiotic exposure, and number of hospital days as independent risk factors for colonization or infection with methicillin-resistant S. aureus. CONCLUSIONS: In our HIV-infected patient population, prior hospitalization, exposure to broad-spectrum antibiotics, presence of a central venous catheter, and dermatologic disease were risk factors for acquisition of methicillin-resistant S. aureus.     

Analytical and biologic variability in measures of hemostasis, fibrinolysis, and inflammation: assessment and implications for epidemiology

CONTEXT: Central venous catheters impregnated with chlorhexidine and silver sulfadiazine have recently been introduced for the prevention of catheter-related infections. However, there remains some uncertainty regarding the efficacy of these catheters because of conflicting reports in the literature. OBJECTIVE: To evaluate the efficacy of chlorhexidine-silver sulfadiazine-impregnated central venous catheters in the prevention of catheter-related bloodstream infection. DATA SOURCES: Studies identified from a computerized search of the MEDLINE database from January 1966 to January 1998, reference lists of identified articles, and queries of principal investigators and the catheter manufacturer. STUDY SELECTION: Randomized trials comparing chlorhexidine-silver sulfadiazine-impregnated central venous catheters with nonimpregnated catheters were included. The outcomes assessed were catheter colonization and catheter-related bloodstream infection confirmed by catheter culture. DATA EXTRACTION: Twelve studies met the inclusion criteria for catheter colonization and included a total of 2611 catheters. Eleven studies with a total of 2603 catheters met the inclusion criteria for catheter-related bloodstream infection. Most patients in these studies were from groups considered to be at high risk for catheter-related infections. Summary statistics were calculated using Mantel-Haenszel methods under a fixed-effects model. DATA SYNTHESIS: The summary odds ratio for catheter colonization was 0.44 (95% confidence interval [CI], 0.36-0.54; P<.001), indicating a significant decrease in catheter colonization associated with impregnated catheters. The studies examining the outcome of primary interest, catheter-related bloodstream infection, had a summary odds ratio of 0.56 (95% CI, 0.37-0.84; P = .005). CONCLUSIONS: Central venous catheters impregnated with a combination of chlorhexidine and silver sulfadiazine appear to be effective in reducing the incidence of both catheter colonization and catheter-related bloodstream infection in patients at high risk for catheter-related infections.     

Confocal laser scanning microscopy of peritoneal catheter surfaces

Surface topography of used (in situ > 12 months) and unused CAPD catheters was studied by scanning electronmicroscopy (SEM) and confocal laser scanning microscopy (CLSM). Microbial biofilm was observed on all used catheters. Disruption and removal of the attached biofilm revealed extensive pitting of the catheter surface and scoring within the catheter pores. Similar, though less extensive, surface defects were present in unused catheters. Examination by CLSM, with software specific to the determination of surface topography, showed used catheters to have a surface microrugosity greater than that of unused catheters (p < 0.0005). Adherence studies with radiolabelled Staphylococcus epidermidis demonstrated increased adherence to used than to unused catheters (p < 0.0005) after 48 h. However, when catheters were pre-treated with spent dialysate there was a substantial reduction in bacterial adherence to either catheter and no significant difference in adherence to used and unused catheters. Surface microrugosity of CAPD catheters increases during use but is unlikely to be an important factor in bacterial adherence in vivo.     

Efficacy of antibiotic-coated catheters in preventing subcutaneous Staphylococcus aureus infection in rabbits

Vascular catheters coated with antiinfective compounds were evaluated as to their ability to prevent Staphylococcus aureus catheter infection in a rabbit model. Zones of inhibition of agar surface-plated S. aureus demonstrated the following hierarchy: dicloxacillin and clindamycin were each better than fusidic acid or chlorhexidine, which were better than ciprofloxacin, cefotaxime, or cefuroxime. In vivo half-lives of inhibitory activity for clindamycin and dicloxacillin were 5.6 and 17.7 h, respectively, with apparent first-order kinetics. Chlorhexidine disappeared in vivo with apparent two-compartment kinetics: first-compartment t1/2, 16.8 h; second-compartment t1/2, 115.6 h. In a rabbit model, dicloxacillin, clindamycin, fusidic acid, and chlorhexidine decreased the risk of infection compared with uncoated control catheters (P < .05). For dicloxacillin, clindamycin, and chlorhexidine, this was true even if the S. aureus inoculation was delayed 48 or 96 h after catheter implantation. These data suggest that vascular catheters with antiinfective coatings should be investigated further in hospitalized patients.     

Simultaneous removal and replacement of infected peritoneal dialysis catheters

Infection is an important complication of peritoneal dialysis that often limits technique survival. Recurrent episodes of peritonitis caused by the same organism may be the result of catheter infection, necessitating removal. We performed 34 single-step catheter replacement procedures in children and young adults for recurrent peritonitis or refractory exit site and tunnel infections. The success rate of the procedure was high (85%), with rare instances of intraoperative contamination. The presence of Staphylococcus aureus infection or exit site and tunnel infection were not risk factors for worse outcome. All patients continued on peritoneal dialysis through catheter change without requiring interval hemodialysis. Eighteen peritoneal dialysis catheters were replaced in a staged procedure with an interval off peritoneal dialysis. There was one early reinfection of the new catheter. Patients with Pseudomonas sp infections were more likely to be treated with a staged procedure; S aureus infections were equally likely to be managed by staged or simultaneous catheter removals. Simultaneous removal and replacement of infected peritoneal dialysis catheters is an effective management strategy when compared with two-step catheter replacements.     

GDNF is abundant in the adult rat gut

This study was performed to assess the value TTC assay in the diagnosis of biomaterial-associated infections. In this assay, soluble colourless TTC is reduced to insoluble red formazan by electron transfer associated with active oxidative bacterial metabolism and is precipitated intracellularly. Microbial adhesion and biofilm formation on the surface of medical prosthetic devices (vesicular and urinary catheters) made of various polymers (PTFE, H-PE, PCW, SL), were determined. The microorganisms which are most often isolated in medical device-associated infections: S. aureus, S. epidermidis, E. faecalis, E. coli, P. vulgaris, P. aeruginosa, C. albicans, were included into the study. The obtained results indicate that the assay using TTC as a metabolic indicator of bacterial biofilm presence, is technically simple to conduct with minimal setup time. Even when classical cultures yielded no bacterial growth, TTC assessments demonstrated bacterial biofilms. TTC assay could be recommended as a quick routine method for confirmation of biomaterial device-associated infection.     

Prevention of intraventricular hemorrhage during CSF shunt revisions by means of a flexible coagulating electrode. A preliminary report

We report the preliminary results of a prospective study in 19 patients (22 procedures) undergoing ventricular catheter replacement at the time of CSF shunt revision to determine the value of intraluminal coagulation by means of a flexible monopolar coagulating electrode in preventing ventricular hemorrhage following catheter removal. These patients had their first shunt implanted during infancy, and underwent shunt revision during the 1-year period between October 1996 and October 1997. Sixteen patients were found to have adherent ventricular catheters, that necessitated the use of diathermy for their removal. In 10 procedures electrocoagulation was applied to the stylet of the ventricular catheter thus permitting tube extraction. In the remaining 8 shunt revisions catheter removal was readily accomplished by coagulation applied to a flexible monopolar endoscopic electrode introduced into the lumen of the tube. Two patients developed mild intraventricular hemorrhage following the use of each of the two methods described above. Both coagulation techniques used during the routine withdrawal of ventricular catheters seem to be equally effective. The flexible coagulating electrode has the additional advantage over the stylet of being moldable, allowing its use in cases in which the catheter does not follow a straight course within the ventricular cavity.     

Dialysis catheter-related septicaemia--focus on Staphylococcus aureus septicaemia

BACKGROUND: Dialysis catheters are a common cause of nosocomial septicaemia in haemodialysis units usually due to staphylococci, of which Staphylococcus aureus is the most pathogenic. In this study, the epidemiology and pathogenesis of dialysis catheter-related infections were studied, and methods to identify patients with these infections were evaluated. METHODS: A one-year prospective study of 67 catheters in 43 haemodialysis patients was performed. Details about patients and catheters were obtained successively during the catheter period, and biochemical parameters expected to be related to infection were measured. After catheter insertion, all patients were screened for nasal carriage of S. aureus, and a culture was taken from the skin overlying the catheter insertion site. Once a week, cultures were taken from the insertion site and from the hub, and aerobic and anaerobic blood cultures were drawn from the catheter. If clinical signs of septicaemia occurred, peripheral blood cultures were also performed, when it was possible. RESULTS: The incidence of septicaemia was 49% (21/43) in patients, and 56% of all cases were caused by S. aureus. The mortality was 14% (3/21) and the incidence of severe secondary complications to septicaemia was 24% (5/31). In all, 80% of all severe complications and 75% of all deaths from septicaemia were due to S. aureus. With respect to S. aureus septicaemia, the predictive values of positive (P) and negative (N) S. aureus cultures were as follows: nasal culture, P=36% (10/28), N=90% (35/39); culture from the insertion site, P=72% (13/18), N=98% (48/49); and culture from the hub, P=75% (3/4), N=83% (52/63). The risk ratio for S. aureus septicaemia was 26.2 (6.1-113), P=0.0001, according to the presence of S. aureus at the insertion site, and 3.3 (0.74-15.1), P=0.12 according to nasal carriage of S. aureus. The frequency of S. aureus phage-type Group 2 (43%) was much higher than the general frequency of this phage-type in Denmark, which is about 23%. Catheter blood cultures were positive although there were no clinical signs of septicaemia in 34% (23/67) of all catheter periods--84% of these were due to coagulase-negative staphylococci. CONCLUSIONS: Dialysis catheter-related S. aureus septicaemia was highly unlikely if the patient had not been carrying S. aureus in the nose or at the insertion site during the time the catheter was in place. The best predictor of dialysis catheter-related S. aureus septicaemia was a positive S. aureus culture from the insertion site. Positive catheter blood cultures unrelated to any clinical signs of septicaemia occurred in one-third of all catheter periods, and 84% of these were due to coagulase-negative staphylococci.     

Flucloxacillin in the treatment of atopic dermatitis

Although colonization of atopic dermatitis by Staphylococcus aureus is universal and bacterial infection is common, it is not known whether antibiotic therapy is helpful in eczematous children who do not have any signs suggestive of bacterial infection. Fifty children aged 1-16 years with atopic dermatitis took part in a randomized double-blind placebo-controlled study of 4 weeks treatment with oral flucloxacillin, with an 8-week follow-up period. The change in the mean of the log10 of the counts/cm2 of S. aureus after 4 weeks of treatment was significantly different for patients receiving treatment, compared with the change for those receiving the placebo (P = 0.008). However, the difference in the change at 14 days after stopping treatment was not significant (P = 0.32). Methicillin-resistant strains of S. aureus were cultured from five children during or after treatment. Flucloxacillin did not improve the symptoms or clinical appearance of atopic dermatitis and only temporarily changed skin colonization by S. aureus.     

The influence of (+/-)-kavain on population spikes and long-term potentiation in guinea pig hippocampal slices

The judicious use of perioperative antibiotic prophylaxis reduces the infectious complications of surgery. However, increased bacterial resistance within hospitals may make antibiotic prophylaxis less effective in the future and alternative strategies are needed. New immunomodulatory agents might prevent wound infections by stimulation of the host immune system. To test this hypothesis, we administered poly-[1-6]-beta-D-glucopyranosyl- [1-3] -beta-D-glucopyranose glucan (PGG glucan), which enhances neutrophil microbicidal activity, intravenously to guinea pigs in doses ranging from 0.015 to 4 mg/kg of body weight on the day before, on the day of, and on the day after intermuscular inoculation with methicillin-resistant strains of Staphylococcus aureus and Staphylococcus epidermidis. Abscesses were identified at 72 h, and median infective doses (ID50) and statistical significance were determined by logistic regression. Guinea pigs receiving PGG glucan and inoculated with methicillin-resistant S. aureus and S. epidermidis exhibited ID50 of as much as 2.5- and 60-fold higher, respectively, than those of control guinea pigs not receiving PGG glucan. Maximal protection was observed with a dose of 1 mg of PGG glucan per kg, and efficacy was reduced at higher as well as at lower PGG glucan doses. Furthermore, a single dose of PGG glucan given 24 h following bacterial inoculation was found to be effective in preventing infection. We conclude that PGG glucan reduces the risk of staphylococcal abscess formation. Neutrophil-activating agents are a novel means of prophylaxis against surgical infection and may be less likely than antibiotics to be affected adversely by the increasing antibiotic resistance of nosocomial pathogens.     

Clinically aggressive metastasizing pleomorphic adenoma: report of two cases

Described are 3 cases of a disconnected ventriculoperitoneal shunting system that was successfully retrieved by using a laparoscopic procedure, with a review of the literature. All patients had symptoms of increased intracranial pressure. Roentgenograms showed disconnection of a ventriculoperitoneal shunt catheter at the connecting device and its migration into the peritoneal cavity. A laparoscope was introduced into the peritoneal cavity using the double puncture procedure and the catheter was extracted in less than 15 minutes. The use of a laparoscope enabled exploration of the entire space of the cavity without any large laparotomy incision. Furthermore, the laparoscopic procedure also easily enabled introduction of a replaceable ventriculoperitoneal shunt catheter into the appropriate portion in the cavity and confirmed the CSF flow into the cavity. Because catheters which have migrated into the cavity might cause an acute abdomen, it is important that they should be removed as soon as possible. It should be kept in mind, during the procedures of extracting catheters, that the inner absorptive surface of the peritoneal cavity must be preserved as much as possible. In this regard, laparoscopic retrieval of disconnected shunt catheters is a promising method.     

The risk of infection associated with intra-arterial catheters for cancer chemotherapy

OBJECTIVE: To determine the frequency of, and risk factors for, infections associated with intra-arterial catheters used for cancer chemotherapy. METHODS: Between September 1992 and September 1995, we conducted a surveillance study of all 807 intra-arterial catheters placed for chemotherapy at our center. The insertion site was disinfected with povidone iodine and alcohol, and the arterial catheter was placed using maximal sterile barrier precautions. Upon removal, all intravascular segments were submitted for semi-quantitative culture. RESULTS: No episodes of catheter-related bloodstream infection (95% confidence interval [CI95], 0%-1.6%) were observed. However, the risk of colonization (>15 colony-forming units) of arterial catheters was 15% (CI95, 12%-17%). Retrospective risk-factor analysis conducted on 224 intra-arterial catheters placed for chemotherapy in 1993 showed that colonization was associated significantly with duration of catheterization (median of 1 day for culture-negative catheters vs median of 4 days for culture-positive catheters, P<.001). Age, gender, prior radiotherapy, underlying cancer, neutropenia, and hypoalbuminemia were not associated with catheter colonization. CONCLUSION: Intra-arterial catheters for cancer chemotherapy placed under maximal sterile barrier precautions for a short period of time are associated with a very low risk of bloodstream infection.     

Conversion of 1-[((S)-2-hydroxy-2-oxo-1,4,2-dioxaphosphorinan-5-yl)methyl]cytosine to cidofovir by an intracellular cyclic CMP phosphodiesterase

In a recent clinical trial, 248 triple-lumen catheters were removed from patients in an intensive care unit, and their tip and subcutaneous segments were cultured by both the sonication and roll plate methods; for 191 of these catheters, flush cultures of all three catheter lumens were also performed. Previously published quantitative endpoints were used to define significant catheter colonization. By using a composite index as a definition of colonization (any of the seven types of cultures meeting quantitative criteria), sonication of the subcutaneous segment was the most sensitive at detecting colonization (58%), followed by sonication of the catheter tip (53%). Sonication of both the subcutaneous and tip segments was 20% more sensitive than sonication of an adjacent catheter segment by the roll plate method (P < 0.05). The greater sensitivity of the sonication method could be attributed to its greater ability than the roll plate method to detect catheter lumen colonization (82 versus 57%, respectively; P = 0.01). A greater number of positive catheter segment cultures were found for colonized catheters from patients with associated bacteremia than for colonized catheters from patients without bacteremia (57 versus 37%; P = 0.004), making any culture method more likely to identify them. For catheters with significant colonization of only one site, the localization was as follows: 36.7% subcutaneous segment, 36.7% catheter lumen, and 26.6% tip segment. These findings suggest that the current practice of culturing a single segment of a central vascular catheter is inadequate and needs to be reexamined. They further suggest that initial colonization of the catheter lumen and tip segments may be more important than previously thought and may require a change in thinking of strategies designed to prevent catheter infection.     

Treatment of bacteria-biofilm graft infection by in situ replacement in normal and immune-deficient states

PURPOSE: Complications of grafts infected with coagulase-negative staphylococci can be eradicated by antibiotic administration, tissue debridement, and in situ graft replacement, but successful treatment may be diminished in a setting of altered immune function. METHODS: In a canine model of an established aortic graft infection from Staphylococcus epidermidis, outcomes after in situ replacement were compared between normal dogs and animals made immune-deficient by administration of azathioprine (50 mg/day) and prednisone (10 mg/day). In situ replacement of an infected infrarenal aortic graft with either antibiotic-bonded (silver-ciprofloxacin: Ag-cipro) or conventional polytetrafluoroethylene (PTFE) grafts was performed in 17 control and 18 immune-deficient animals. RESULTS: Four weeks after implantation of a Dacron graft colonized with a biofilm of S. epidermidis, all study animals demonstrated a bacterial biofilm infection with perigraft inflammation or abscess, and in immune-suppressed dogs the incidence of perianastomotic aortitis was increased (p < 0.05). Six weeks after in situ replacement both the Ag-cipro and conventional PTFE grafts were healed without signs of infection in controls, but anatomic evidence of persistent infection and increased S. epidermidis recovery was observed in immune-suppressed animals that underwent in situ replacement of a standard (five of seven) versus antibiotic-bonded (one of 11) PTFE graft (p < 0.006). Overall in situ replacement with an antibiotic-bonded graft yielded a lower frequency of S. epidermidis recovery (two of 19 Ag-cipro graft biofilm with positive culture results versus nine of 16 conventional graft biofilm with positive culture results; (p < 0.003). CONCLUSIONS: This study supports the efficacy of in situ replacement for low-grade graft infections caused by S. epidermidis in normal hosts and demonstrates superiority of antibiotic-bonded grafts in immune-deficient hosts.