Graft Infectivity of Rifampin and Silver-Bonded Polyester Grafts to MRSA Contamination

Significance and current approaches to vascular graft infection

Vascular graft/endograft infection (VGEI) is a constant in cardiovascular surgery with published rates between 1 and 5%. Every graft type and anatomical location is a potential target for infectious complications. These patients are sick patients with high frailty burden. Management of VGEI entails a multidisciplinary and multimodality approach. Here we review some aspects of the problem of VGEI including prevention, diagnosis, and surgical therapy with focus on recent developments in the field.

Complications of e-PTFE Grafts in LDLT; Evaluation of Case Series

BACKGROUND

The expanded polytetrafluoroethylene (ePTFE) grafts are used to drain anterior sector veins during the living donor liver transplantation procedure. We aimed to analyze the potentially life-threatening complications, such as the infection and migration of ePTFE grafts.

METHODS

A total of 1264 liver transplantations (LTs) were performed for 1097 adult and 167 pediatric liver failure cases. In total, 1169 living and 95 cadaveric liver transplantation procedures were performed between 2011 and 2021. Right liver transplantation was performed in 1016 cases, including 1002 living donors and 14 cadaveric split right livers. Cadaveric LT was performed in 81 cases.

RESULTS

For 1002 right living liver grafts, 905 vascular grafts were used during the backtable for anterior sector outflow venoplasty. The most commonly drained segments were 5 and 8 (472 cases); there were isolated (5 or 8) and multiple drained segments. Vascular graft migration was described in 7 of 905 (0.77%) patients.

CONCLUSIONS

Although complication rates regarding ePTFE grafts are low, there are serious life-threatening causes of morbidity and mortality. We recommend cushioning the vascular graft with the omentum, which is effective in preventing graft migration.

A systematic review of preclinical data regarding commercial silver-coated vascular grafts

OBJECTIVE

Vascular graft infection (VGI) is a serious complication with high mortality and morbidity rates. Several measures could be taken to decrease this risk, including the use of silver-containing vascular grafts. However, to date, no clinical advantages have been reported. This study reviews the outcome of preclinical studies focusing on the role of commercially available silver-coated grafts in the prevention of VGI.

METHODS

A systematic review was performed with a focus on the preclinical role of commercially available silver-coated vascular grafts in the prevention and treatment of VGI. A comprehensive search was conducted in Medline, Embase, and Web of Science.

RESULTS

Nine in vitro and five in vivo studies were included. Two commercial grafts were used (INTERGARD SILVER and Silver Graft). In vitro studies used both gram-positive and gram-negative strains. A positive antimicrobial effect was observed in seven of nine studies (77.8%). A delayed antifungal effect against Candida species was observed in vitro, but disappeared when adding serum proteins. In vivo studies witnessed a microbicidal effect in two out of five studies (40%), but only tested a single causative pathogen (ie, Staphylococcus aureus).

CONCLUSIONS

Both in vitro and in vivo studies demonstrated conflicting and mixed results concerning the antimicrobial efficacy of commercially available silver-containing grafts in the prevention of VGI. In general, the study setup was heterogeneous in the different articles. Given the lack of convincing preclinical evidence and their poor performance in clinical studies, more data are needed at this time to guide the appropriate use of silver grafts.

Pre-clinical in vivo Models of Vascular Graft Coating in the Prevention of Vascular Graft Infection: A Systematic Review

OBJECTIVE

Vascular graft infection (VGI) remains an important complication with a high mortality and morbidity rate. Currently, studies focusing on the role of vascular graft coatings in the prevention of VGI are scarce. Therefore, the aims of this study were to survey and summarise key features of pre-clinical in vivo models that have been used to investigate coating strategies to prevent VGI and to set up an ideal model that can be used in future preclinical research.

DATA SOURCES

A systematic review was conducted in accordance with the Preferred reporting items for Systematic Reviews and Meta-Analysis guidelines. A comprehensive search was performed in MEDLINE (PubMed), Embase, and Web of Science.

REVIEW METHODS

For each database, a specific search strategy was developed. Quality was assessed with the Toxicological data Reliability Assessment Tool (ToxRTool). The type of animal model, graft, coating, and pathogen were summarised. The outcome assessment in each study was evaluated.

RESULTS

In total, 4 667 studies were identified, of which 94 papers focusing on in vivo testing were included. Staphylococcus aureus was the organism most used (n = 65; 67.7%). Most of the graft types were polyester grafts. Rifampicin was the most frequently used antibiotic coating (n = 43, 48.3%). In the outcome assessment, most studies mentioned colony forming unit count (n = 88; 91.7%) and clinical outcome (n = 72; 75%). According to the ToxRTool, 21 (22.3%, n = 21/94) studies were considered to be not reliable.

CONCLUSION

Currently published in vivo models are very miscellaneous. More attention should be paid to the methodology of these pre-clinical reports when transferring novel graft coatings into clinical practice. Variables used in pre-clinical reports (bacterial strain, duration of activity coating) do not correspond well to current clinical studies. Based on the results of this review, a proposal for a complete and comprehensive set up for pre-clinical invivo testing of anti-infectious properties of vascular graft coatings was defined.

Polyester Vascular Graft Material and Risk for Intracavitary Thoracic Vascular Graft Infection1

Prosthetic vascular graft infections of the thoracic aorta are rare but can be fatal. Our comparison of collagen- and gelatin-coated grafts showed that collagen-coated grafts were associated with increased biofilm formation and bacterial adherence in vitro and with higher rates of perioperative vascular graft infections in vivo.

Assessing the Safety of Expanded Polytetrafluoroethylene Synthetic Grafts in Living Donor Liver Transplantation: Graft Migration Into Hollow Viscous Organs - Diagnosis and Treatment Options

Background

Our recent studies have highlighted the importance and safety of backtable venoplasty for middle hepatic vein (MHV) and inferior right hepatic veins (IRHV) reconstruction using expanded polytetrafluoroethylene (ePTFE) vascular grafts. In this study, we aim to analyze the complications associated with ePTFE graft use and discuss the management of the rare, but, potentially life threatening complications directly related to ePTFE conduits.

Material/Methods

From January 2012 to October 2015 a total of 397 patients underwent living donor liver transplantation (LDLT). The ePTFE vascular grafts were used during the backtable venoplasty for outflow reconstruction in 262 of the liver allografts. Recipients who developed ePTFE-related complications were analyzed.

Results

ePTFE-related complications developed in 1.52% (4/262) of the patients. One patient (0.38%) developed complete thrombosis with sepsis at 24 months post-transplantation and died due to multiorgan failure. Three patients (1.1%) developed graft migration into the second portion of the duodenum, without overt peritonitis. Surgical exploration and ePTFE graft removal was done in all the patients. One patient died due to overwhelming sepsis.

Conclusions

ePTFE graft migration into the duodenum causing perforation is a new set of complications that has been recently described in LDLT and can be treated effectively by surgical removal of the infected vascular graft and duodenal perforation closure. Despite of such complications, in our experience, ePTFE use in LDLT continues to have wide safety margin, with a complication rate of only 1.52%.

A Novel Mouse Model of Staphylococcus aureus Vascular Graft Infection: Noninvasive Imaging of Biofilm Development in Vivo

Staphylococcus aureus causes very serious infections of vascular grafts. Knowledge of the molecular mechanisms of this disease is largely lacking because of the absence of representable models. Therefore, the aim of this study was to set up a mouse model of vascular graft infections that closely mimics the human situation. A catheter was inserted into the right carotid artery of mice, which acted as a vascular graft. Mice were infected i.v. using 8 different S. aureus strains, and development of the infection was followed up. Although all strains had varying abilities to form biofilm in vitro and different levels of virulence in mice, they all caused biofilm formation on the grafts. This graft infection was monitored using magnetic resonance imaging (MRI) and ¹⁸F-fluordeoxyglucose positron emission tomography (FDG-PET). MRI allowed the quantification of blood flow through the arteries, which was decreased in the catheter after infection. FDG-PET revealed high inflammation levels at the site of the catheter after infection. This model closely resembles the situation in patients, which is characterized by a tight interplay between pathogen and host, and can therefore be used for the testing of novel treatment, diagnosis, and prevention strategies. In addition, combining MRI and PET with microscopic techniques provides an appropriate way to characterize the course of these infections and to precisely analyze biofilm development.

In situ revascularisation for femoropopliteal graft infection: ten years of experience with silver grafts

Purpose

The purpose of this study was to analyze clinical outcome of patients for femoropopliteal graft infection who were treated by in situ reconstruction with a silver-coated prosthesis.

Basic methods

From December 2001 to December 2011, 27 patients were treated for femoropopliteal graft infection. Twenty patients (74%) were male and seven (26%) were female. Mean age was 65 years. The primary endpoint was recurrence of infection. Secondary endpoints were early and late mortality and morbidity, primary graft patency, major amputation rates and patient survival.

Principal findings

Early reinfection occurred in 11% and late in 8% of patients. Perioperative mortality was 7% and late was 4%. Above-knee amputation was performed in 4% of patients during early postoperative course and in 12% of patients during follow-up. Early and late graft patency was 96% and 72%, respectively.

Conclusions

Results of in situ implantation of silver-coated grafts for femoropopliteal prosthesis infection are according to our opinion acceptable, but the risk of reinfection remains.

A pilot study of a triple antimicrobial-bonded Dacron graft for the prevention of aortic graft infection

OBJECTIVE

Perioperative infection of an aortic graft is one of the most devastating complications of vascular surgery, with a mortality rate of 10% to 30%. The rate of amputation of the lower limbs is generally >25%, depending on the graft material, the location of the graft and infection, and the bacterial virulence. In vitro studies suggest that an antibiotic-impregnated graft may help prevent perioperative graft infection. In a pilot animal study, we tested a locally developed technique of bonding Dacron aortic grafts with three antimicrobial agents to evaluate the ensuing synergistic preventive effect on direct perioperative bacterial contamination.

METHODS

We surgically implanted a 6-mm vascular knitted Dacron graft in the infrarenal abdominal aorta of six Sinclair miniature pigs. Two pigs received unbonded, uninoculated grafts; two received unbonded, inoculated grafts; and two received inoculated grafts that were bonded with chlorhexidine, rifampin, and minocycline. Before implantation, the two bonded grafts and the two unbonded grafts were immersed for 15 minutes in a 2-mL bacterial solution containing 1 to 2 × 10(7) colony-forming units (CFU)/mL of Staphylococcus aureus (ATCC 29213). Two weeks after graft implantation, the pigs were euthanized, and the grafts were surgically excised for clinical, microbiologic, and histopathologic study.

RESULTS

The two bonded grafts treated with S aureus showed no bacterial growth upon explant, whereas the two unbonded grafts treated with S aureus had high bacterial counts (6.25 × 10(6) and 1.38 × 10(7) CFU/graft). The two control grafts (unbonded and untreated) showed bacterial growth (1.8 × 10(3) and 7.27 × 10(3) CFU/graft) that presumably reflected direct, accidental perioperative bacterial contamination; S cohnii ssp urealyticus and S chromogenes, but not S aureus, were isolated. The histopathologic and clinical data confirmed the microbiologic findings. Only pigs that received unbonded grafts showed histopathologic evidence of a perigraft abscess.

CONCLUSIONS

Our results suggest that bonding aortic grafts with this triple antimicrobial combination is a promising method of reducing graft infection resulting from direct postoperative bacterial contamination for at least 2 weeks. Further studies are needed to explore the ability of this novel graft to combat one of the most feared complications in vascular surgery.

Antibiotic-impregnated grafts for aortic reconstruction

An infected aorta, or aortic graft, is a challenge to manage. Extra-anatomical bypass followed by resection of the infected aorta has been considered standard practice. Outcomes are far from ideal and anatomical constraints make this impossible at the visceral and thoracic aorta. In situ aortic repair is an alternative and can be accomplished in most cases. Use of this technique has been tempered by concerns of graft durability and reinfection. In vitro and in vivo laboratory experiments have demonstrated antibiotics can be bound to polytetrafluoroethylene and Dacron aortic grafts. In animal models, antibiotic-soaked grafts were resistant to infection when seeded with an intravenous bacteria challenge. Purulent, infected aortic grafts created in animal models by direct bacteria inoculation could be successfully replaced in situ with infection-resistant antibiotic-soaked Dacron grafts. The antibiotic of choice is rifampin, which readily binds to commercially available, off-the-shelf gelatin- or collagen-impregnated Dacron. In humans, rifampin-soaked Dacron has not only been used to reconstruct the aorta in the face of infection, but also in elective aortic reconstruction as a prophylaxis against future infection. Outcomes from case series are difficult to interpret because of the heterogeneous nature of patients presenting with aortic infections. Thirty-day mortality ranges from 7% to 21% and morbidity from 2% to 60%. Amputations are rarely seen in these cases, but are common in extra-anatomical bypass from graft occlusion. Reinfection of the rifampin grafts are seen in 4% to 22% of patients, and 5-year survival is near 50%. In the future, the utility of rifampin-soaked Dacron will have to be tested against the emergence of antibiotic-resistant bacteria. Improvements in alternative conduits, such as cryopreserved aortic grafts, may diminish the use of antibiotic-soaked grafts, but it will remain a useful tool in the vascular surgeon's armamentarium.

A silver nanocomposite biomaterial for blood-contacting implants

Cardiovascular implants must resist infection and thrombosis. A nanocomposite polymeric material [polyhedral-oligomeric-silsesquioxane-poly(carbonate-urea)urethane; POSS-PCU] demonstrates ideal properties for cardiovascular applications. Silver nanoparticles or nanosilver (NS) are recognized for efficient antibacterial properties. This study aims to determine the influence of NS integrated POSS-PCU on thrombogenicity. Silver nitrate was reduced with dimethylformamide and stabilized by the inclusion of fumed silica nanoparticles to prevent aggregation of NS and were incorporated into POSS-PCU to form a range of POSS-PCU-NS concentrations (by weight); 0.20% (NS16), 0.40% (NS32), 0.75% (NS64), and 1.50% (NS128). Surface wettability was determined with sessile-drop water contact angles. Platelets were introduced onto test samples and Alamar Blue (AB), mitochondrial-activity assay, quantified the degree of platelet adhesion whilst platelet-factor-4 (PF4) ELISA quantified the degree of platelet activation. Thromboelastography (TEG) determined the profiles of whole blood kinetics while hemolysis assay demonstrated the degree of blood compatibility. Increasing levels of NS induced greater hydrophilicity. A concentration dependant decrease in platelet adhesion and activation was observed with AB and PF4 readings, respectively. TEG demonstrated that the antithrombogenic properties of POSS-PCU were retained with POSS-PCU-NS16, and enhanced with POSS-PCU-NS32, but was reduced with POSS-PCU-NS64 and POSS-PCU-NS128. POSS-PCU-NS64 and POSS-PCU-NS128 demonstrated a hemolytic tendency, but no hemolysis was observed with POSS-PCU-NS16 and POSS-PCU-NS32. Overall, POSS-PCU-NS32 rendered potent antithrombogenic properties.

Rifampicin-soaked silver polyester versus expanded polytetrafluoro-ethylene grafts for in situ replacement of infected grafts in a porcine randomised controlled trial

BACKGROUND

To compare the efficacy of in situ replacement with rifampicin-soaked silver-coated polyester (RSSCP) to that of expanded polytetrafluoroethylene (ePTFE) graft replacements in a porcine model for early aortic prosthetic vascular graft infection (PVGI).

MATERIAL AND METHODS

Sixty pigs received polyester or silver-coated grafts with an 8 mm diameter implanted end-to-end in the infrarenal aorta, and the grafts were inoculated with approximately 10(6)Staphylococcus aureus. All developed S. aureus PVGI. Two weeks later, the 52 surviving pigs were randomised to undergo in situ graft replacement with ePTFE or RSSCP grafts followed by oral administration of 300 mg rifampicin and 750 mg ciprofloxacin twice a day, postoperatively. After three weeks, all pigs were sacrificed. In situ perigraft swabs and graft material were analysed for S. aureus quantitatively.

RESULTS

Only one out of 25 RSSCP grafts were infected with S. aureus, whereas 15 of 27 ePTFE grafts were infected after 3 weeks (OR = 0.022, 95% CI: 0.002, 0.219, P = 0.001).

CONCLUSIONS

In situ replacement with RSSCP grafts and oral rifampicin plus ciprofloxacin is more efficiency in eradicating S. aureus PVGI than ePTFE grafts treated with same oral antibiotics in a porcine aortic PVGI model.

Incidence and clinical implication of nosocomial infections associated with implantable biomaterials - catheters, ventilator-associated pneumonia, urinary tract infections

Health care associated infections, the fourth leading cause of disease in industrialised countries, are a major health issue. One part of this condition is based on the increasing insertion and implantation of prosthetic medical devices, since presence of a foreign body significantly reduces the number of bacteria required to produce infection. The most significant hospital-acquired infections, based on frequency and potential severity, are those related to procedures e.g. surgical site infections and medical devices, including urinary tract infection in catheterized patients, pneumonia in patients intubated on a ventilator and bacteraemia related to intravascular catheter use. At least half of all cases of nosocomial infections are associated with medical devices.Modern medical and surgical practices have increasingly utilized implantable medical devices of various kinds. Such devices may be utilized only short-time or intermittently, for months, years or permanently. They improve the therapeutic outcome, save human lives and greatly enhance the quality of life of these patients. However, plastic devices are easily colonized with bacteria and fungi, able to be colonized by microorganisms at a rate of 0.5 cm per hour. A thick biofilm is formed within 24 hours on the entire surface of these plastic devices once inoculated even with a small initial number of bacteria.The aim of the present work is to review the current literature on causes, frequency and preventive measures against infections associated with intravascular devices, catheter-related urinary tract infection, ventilator-associated infection, and infections of other implantable medical devices. Raising awareness for infection associated with implanted medical devices, teaching and training skills of staff, and establishment of surveillance systems monitoring device-related infection seem to be the principal strategies used to achieve reduction and prevention of such infections. The intelligent use of suitable antiseptics in combination with medical devices may further support reduction and prevention of such infections. In addition to reducing the adverse clinical outcomes related with these infections, such reduction may substantially decrease the economic burden caused by device-related infection for health care systems.

[Mid-term results of silver-coated Dacron graft implantation in aortic and lower extremity revascularization]

BACKGROUND

Prosthetic graft infection or the need for reconstructive arterial surgery in septic condition is a challenging situation in vascular surgery. Recent introduction of silver coated polyester graft has meant a new therapeutic option in selecting the type of graft for revascularization. In this study we analyzed the short and midterm outcome of using silver coated grafts in aortic and lower extremity arterial reconstructions (mortality, graft occlusion, graft infection, amputation).

MATERIALS AND METHODS

In a single center retrospective study we implanted 42 silver coated Dacron grafts (InterGard Silver Dacron prosthesis). The indication of silver graft implantation was graft infection in 17, aorto-duodenal fistula in 7, septic condition caused by gangrene in 16 cases and in 2 cases infection was not established.

RESULTS

Forty silver grafts were implanted in 40 patients with diagnosed infection. The mean age was 62 years (35-81 years), 70% were men. Long term follow-up data were available in 29 patients; the mean follow-up time was 36.76 months. Early (within 30 days of surgery) death occurred in 3 and late death in 11 cases (8 and 38%). Early graft occlusion was noticed in 8 and late occlusion in 2 cases (20 and 7%). Reinfection was diagnosed in 7% of the cases in the early and the midterm period as well. Eight amputations were indicated in the early postoperative period (5 major and 3 minor) and 28% of the patients required major amputation during the follow-up.

CONCLUSIONS

Silver coated Dacron graft means a valuable therapeutic option with good rate of infection control in the treatment of graft infection and septic condition in the lack of autologous graft material in this high risk population.

Prevention of early vascular graft infection using regional antibiotic release

BACKGROUND

Infections after prosthetic replacement of the aorta remain a serious and life-threatening complication. The only appropriate treatment is the surgical removal of the infected prosthesis. Accordingly, there is a need for new procedures to prevent the infection of vascular prostheses. This in vitro experiment investigated the effect of the pretreatment of vascular prostheses with antibiotics (daptomycin or baneocin) and the effect of antibiotics combined with fibrin sealant as possible prophylaxis of perioperative graft infection.

METHODS

Untreated prostheses served as controls. Pretreated prostheses of double woven velour vascular grafts were contaminated with Staphylococcus epidermidis, and colony-forming units were counted each day (CFU/mL).

RESULTS

The period of sterility differed significantly as a function of the pretreatment. Uncoated prostheses were immediately non-sterile and exhibited 2.63 ± 0.61 × 10(5) CFU/mL. Baneocin pretreatment resulted in sterility for 1.7 ± 0.6 (95% confidence interval (CI) 1.0-2.4) d before we detected 2.14 ± 0.57 × 10(5) CFU/mL on the prostheses. Pretreatment with daptomycin yielded 2.9 ± 0.4 (CI 2.6-3.2) and fibrin sealant/baneocin compound yielded 3.1 ± 0.3 (CI 2.9-3.3) d of sterility, after which 1.81 ± 0.86 × 10(5) CFU/mL and 1.04 ± 0.77 × 10(5) CFU/mL were recorded. Finally, pretreatment with fibrin sealant/daptomycin led to sterility for 7.1 ± 0.3 (CI 6.9-7.3) d, after which 0.77 ± 0.60 × 10(5) CFU/mL were observed on the prostheses.

CONCLUSIONS

The risk of vascular graft infection is reduced by pretreating the prostheses with antibiotics. The antibiotic/fibrin compound exhibited an effect of delayed antibiotic release. Vascular prostheses should therefore be pretreated with antibiotic solution to reduce bacterial adhesion. This procedure might be an effective prophylaxis for perioperative vascular graft infection and provides suitable protection for the prosthetic material.

Bacterial translocation across ePTFE vascular graft surfaces

OBJECTIVES

Vascular graft infections arise from bacterial colonization of either the external or internal graft surfaces. We assessed whether methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli could translocate through pores of ePTFE grafts.

METHODS

To assess translocation from the internal to the external surface, we placed 10(5) cfu of bacterial suspension inside ePTFE graft segments and suspended them in sterile broth for 72 h. To assess translocation from the external to the internal surface, we placed sterile broth inside ePTFE segments, and incubated them for 72 h in a bacterial suspension (10(5) cfu/mL). At 72 h, in addition to culturing the sterile broth and bacterial suspensions, the external and internal surfaces were first qualitatively cultured separately and then quantitatively cultured by sonication.

RESULTS

At 72 h, the sterile broth remained sterile. The bacterial suspensions yielded 10(7)-10(9) cfu/mL. Graft cultures indicated that colonization of one surface with either organism did not result in bacterial translocation to the other surface. Quantitative bacterial counts of the external vs. internal surfaces were significantly different (p < 0.01).

CONCLUSIONS

MRSA and E. coli do not translocate across ePTFE graft surfaces. These in-vitro findings help elucidate the pathogenesis of graft infections and prompt conduction of validation studies in-vivo.

ECM-based materials in cardiovascular applications: Inherent healing potential and augmentation of native regenerative processes

The in vivo healing process of vascular grafts involves the interaction of many contributing factors. The ability of vascular grafts to provide an environment which allows successful accomplishment of this process is extremely difficult. Poor endothelisation, inflammation, infection, occlusion, thrombosis, hyperplasia and pseudoaneurysms are common issues with synthetic grafts in vivo. Advanced materials composed of decellularised extracellular matrices (ECM) have been shown to promote the healing process via modulation of the host immune response, resistance to bacterial infections, allowing re-innervation and reestablishing homeostasis in the healing region. The physiological balance within the newly developed vascular tissue is maintained via the recreation of correct biorheology and mechanotransduction factors including host immune response, infection control, homing and the attraction of progenitor cells and infiltration by host tissue. Here, we review the progress in this tissue engineering approach, the enhancement potential of ECM materials and future prospects to reach the clinical environment.

Results from the First in Man German Pilot Study of the Silver Graft, a Vascular Graft Impregnated with Metallic Silver

The purpose of this study was to assess the safety of a novel vascular prosthesis in 50 patients who underwent inguinal and infrainguinal vascular reconstructions. The safety data were based on ultrasound Doppler data at 2 and 18 months to quantify the graft-tissue integration in this patient cohort. Between August 9, 2005, and January 25, 2006, 50 patients underwent inguinal or infrainguinal reconstructions with the Silver Graft (SG; B. Braun Melsungen AG, B. Braun Aesculap AG, Tuttlingen, Germany) in six vascular centers. All participating centers received the metallic silver-coated polyester graft (SG) with a diameter of 8 mm and a total length of 60 cm, which was length adjusted to fit the patient's anatomy and the planned vascular reconstruction. The mean patient age was 69.1 ± 9.0 years, the male inclusion rate was 72.0%, and the Fontaine classifications were stage IV (16%), stage III (14%), stage IIb (66%), and stage IIa (4%), whereas aneurysm repairs amounted to 4%. In-hospital results revealed the presence of minimal perigraft fluid in 14.0% of all cases (7 of 50). At the 2-month follow-up, perigraft fluid was detected in one patient (1 of 50). At 18 months, a single case of minimal perigraft fluid was detected in an asymptomatic patient. Wound healing was accomplished at discharge in 96% of all patients, whereas at the 2-month follow-up, no signs of wound infection or irritation could be detected. The accumulated primary patency rates were 94% at 2 months and 88% at 18 months. The available clinical data on perigraft fluid as a marker for graft-tissue incorporation at 2 and 18 months, patency, and wound healing are comparable to those of other relevant clinical results with polyester grafts and support the safety of the metallic SG in the studied patient population with inguinal and infrainguinal reconstructions. However, it cannot be guaranteed that all graft infections can be avoided with the SGs.

Prevention of Staphylococcus aureus graft infection by a new gelatin-sealed vascular graft prebonded with antibiotics

OBJECTIVE

The aim of this study was to evaluate the efficacy of a new gelatin-sealed graft prebonded with two antibiotics in resisting infection with Staphylococcus aureus (S aureus) A980142 after direct bacterial application in a dog model.

METHODS

Twelve 6.0-mm polyester grafts were implanted in dogs end-to-end into the infrarenal aorta. The dogs were divided into two groups. A test group (n = 6) received experimental antibiotic-bonded gelatin-sealed knitted polyester grafts, loaded with two antibiotics, rifampin and tobramycin. A control group (n = 6) received commercial gelatin-sealed knitted polyester grafts. At the end of graft implantation, 50 mul of a 1.8 x 10(4) CFU/mL S aureus solution were instilled directly over the graft. One week after implantation, grafts were harvested with sterile technique. Quantitative cultures were obtained from all the harvested grafts. The results were expressed as colony-forming units per cm(2) of surface of the graft. Bacteriological study was also performed on various tissue samples. The chi(2) test was used to compare the culture proven infection of control and antibiotics-bonded grafts.

RESULTS

Mean inoculum size was similar in the two groups of dogs. Five of the six control grafts grew S aureus A980142 at the time of graft removal, whereas none of the six antibiotic-bonded gelatin-sealed grafts were infected (P = .0192). None of the organ samples were infected in the group implanted with antibiotic-bonded grafts, whereas 15/34 samples grew S. aureus in the control group.

CONCLUSION

These results indicate that this gelatin sealed graft prebonded with two antibiotics resists infection caused by S aureus graft contamination in a dog model.