Limitations in the use of rifampicin-gelatin grafts against virulent organisms

Revascularization and Digestive Tract Repair in Secondary Aortoenteric Fistula Using a Single-Center in Situ Revascularization Strategy

BACKGROUND

Information regarding optimal revascularization and digestive tract repair in secondary aortoenteric fistula (sAEF) remains unclear. Thus, reporting treatment outcomes and presenting comprehensive patient details through a structured treatment approach are necessary to establish a treatment strategy for this rare, complex, and fatal condition.

METHODS

We performed a single-center retrospective review of consecutive sAEF managed based on our in situ revascularization and intestinal repair strategy. The primary endpoint of this study was all-cause mortality, and secondary endpoints were the incidence of in-hospital complications and midterm reinfections.

RESULTS

Between 2007 and 2020, 16 patients with sAEF, including 13 men (81%), underwent in situ revascularization and digestive tract repair. The median follow-up duration for all participants was 36 (interquartile range, 6-62) months. Among the participants, 81% (n = 13), 13% (n = 2), and 6% (n = 1) underwent aortic reconstruction with rifampin-soaked grafts, unsoaked Dacron grafts, and femoral veins, respectively. The duodenum was the most commonly involved site in enteric pathology (88%; n = 14), and 57% (n = 8) of duodenal breaks were repaired by a simple closure. Duodenum's second part-jejunum anastomosis was performed in 43% of patients (n = 6), and 19% of the patients (n = 3) died perioperatively. In-hospital complications occurred in 88% patients (n = 14), and the most frequent complication was gastrointestinal. Finally, 81% patients (n = 13) were discharged home. Oral antibiotics were administered for a median duration of 5.7 months postoperatively; subsequently, the participants were followed up carefully. Reinfection was detected in 6% of the patients (n = 1) who underwent reoperation without any complications. The 1-year and 3-year overall survival rates of participants were 75% (n = 12) and 75% (n = 9), respectively, and no sAEF-related deaths occurred, except perioperative death.

CONCLUSIONS

Surgical intervention with contemporary management based on our vascular strategy and digestive tract procedure may be a durable treatment for sAEF.

Successful surgical treatment of Stanford type A aortic dissection due to Salmonella aortitis

BACKGROUND

Salmonella spp. cause infectious aortitis through the hematogenous spread of an intestinal Salmonella infection. Salmonella aortitis can result in extensive tissue damage in the aorta leading to complications including dissection, abscess formation, pseudoaneurysms, and rupture, which require early diagnosis and treatment with both surgery and antibiotic therapy.

CASE PRESENTATION

We report a case of Salmonella aortitis complicated by Stanford type A aortic dissection. A 62-year-old man with a history of heroin use presented with chest pain, epigastric pain and vomiting. The computed tomography scan showed Stanford type A aortic dissection without malperfusion. At the time of surgery, an aortic dissection with purulent fluid and contained rupture was noted in the ascending aorta. Fluid culture was consistent with Salmonella. A composite valve-graft conduit aortic root replacement with ascending aorta and hemiarch replacement was performed. The patient recovered well and was discharged on long-term antibiotics.

CONCLUSIONS

This rare case of a Stanford type A aortic dissection with contained rupture due to Salmonella aortitis was successfully treated with emergent surgery and antibiotic therapy.

Bacteriophages for the Treatment of Graft Infections in Cardiovascular Medicine

Bacterial infections of vascular grafts represent a major burden in cardiovascular medicine, which is related to an increase in morbidity and mortality. Different factors that are associated with this medical field such as patient frailty, biofilm formation, or immunosuppression negatively influence antibiotic treatment, inhibiting therapy success. Thus, further treatment strategies are required. Bacteriophage antibacterial properties were discovered 100 years ago, but the focus on antibiotics in Western medicine since the mid-20th century slowed the further development of bacteriophage therapy. Therefore, the experience and knowledge gained until then in bacteriophage mechanisms of action, handling, clinical uses, and limitations were largely lost. However, the parallel emergence of antimicrobial resistance and individualized medicine has provoked a radical reassessment of this approach and cardiovascular surgery is one area in which phages may play an important role to cope with this new scenario. In this context, bacteriophages might be applicable for both prophylactic and therapeutic use, serving as a stand-alone therapy or in combination with antibiotics. From another perspective, standardization of phage application is also required. The ideal surgical bacteriophage application method should be less invasive, enabling highly localized concentrations, and limiting bacteriophage distribution to the infection site during a prolonged time lapse. This review describes the latest reports of phage therapy in cardiovascular surgery and discusses options for their use in implant and vascular graft infections.

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.

Endovascular treatment for mycotic aneurysm using pyoktanin- applied devices

Background

Mycotic thoracic aortic aneurysm is an extremely rare but serious disease because it can easily rupture and has a high mortality rate. The standard therapy for it comprises graft replacement and debridement using systemic antibiotics; nonetheless, this has a high mortality rate and complications. Endovascular aortic repair is considered a bridging therapy before open surgery. However, we have used it at our institution for the radical treatment of mycotic thoracic aortic aneurysm utilizing pyoktanin (methylrosanilide chloride)-applied devices. Thus, the aim of this study was to report our clinical experience with pyoktanin-applied thoracic endovascular aortic repair for the treatment of mycotic thoracic aortic aneurysm, including its effects.

Methods

From April 2017 to July 2019, we performed thoracic endovascular aortic repair using pyoktanin for eight cases of mycotic thoracic aortic aneurysm using Valiant®. During device preparation before insertion, pyoktanin was flushed from the side port instead of saline containing heparin.

Results

There were no operative deaths, recurrences of infection, or major complications. Two cases died from pneumonia and cancer; the other six cases were alive during the follow-up period.

Conclusions

Pyoktanin-applied thoracic endovascular aortic repair for mycotic thoracic aortic aneurysm treatment is effective. However, the appropriate use of antibiotics and bundled therapy is necessary at present.

Efficacy of antiseptic impregnation of aortic endografts with rifampicin compared to silver against in vitro contamination with four bacteria that frequently cause vascular graft infections

OBJECTIVE

This in vitro study investigates the antimicrobial efficacy of impregnation of commercially available aortic endografts (EG) with rifampicin (RIF) and nanocolloidal silver.

METHODS

Endografts were flushed with 50 mL of RIF 600 mg, 70 mL of a silver-based aqueous solution (AG), or 50 mL of phosphate-buffered saline (PBS) over 15 minutes. Endografts were then retrieved from the sheath and cut in 1 × 1 cm sized graft units (n = 80 of each impregnation), which were then incubated for 1 hour separately with inoculates containing 10⁶ or 10³ bacteria per milliliter (bact/mL) of each of the following bacteria: Staphylococcus epidermidis, Escherichia coli, multisensitive Staphylococcus aureus, and Pseudomonas aeruginosa. After sonication of the graft units, bacterial counts were measured by plating out twice the sonication solution on Mueller-Hinton plates.

RESULTS

RIF showed a statistically significant decrease of colony forming units per milliliter for all four bacterial strains in both concentrations compared with PBS and AG, except for 10³ bact/mL of E coli. AG showed a significant decrease of colony forming units per milliliter compared with PBS only for 10⁶ bact/mL of E coli and was statistically significantly inferior to RIF for all four bacterial strains in both concentrations with the exception of E coli at a concentration of 10³ bact/mL.

CONCLUSIONS

This in vitro study demonstrated infectivity resistance of aortic EG after flushing with RIF. Moreover, the feasibility of flushing aortic EG with a new silver-based agent could be demonstrated, but without statistically significant antimicrobial efficacy compared with native EG.

In situ revascularization with rifampicin-soaked silver polyester graft for aortic infection: Results of a retrospective monocentric series of 18 cases

OBJECTIVE

To evaluate the short and long-term results of in situ prosthetic graft treatment using rifampicin-soaked silver polyester graft in patients with aortic infection.

MATERIAL AND METHOD

All the patients surgically managed in our center for an aortic infection were retrospectively analyzed. The primary endpoint was the intra-hospital mortality, secondary outcomes were limb salvage, persistent or recurrent infection, prosthetic graft patency, and long-term survival.

RESULTS

From January 2004 to December 2015, 18 consecutive patients (12 men and 6 women) were operated on for aortic infection. Six mycotic aneurysms and 12 prosthetic infections, including 8 para-entero-prosthetic fistulas, were treated. In 5 cases, surgery was performed in emergency. During the early postoperative period, we performed one major amputation and two aortic infections were persistent. Intra-hospital mortality was 27.7%. The median follow-up among the 13 surviving patients was 26 months. During follow-up, none of the 13 patients presented reinfection or bypass thrombosis.

CONCLUSION

This series shows that in situ revascularization with rifampicin-soaked silver polyester graft for aortic infection have results in agreement with the literature in terms of intra-hospital mortality with a low reinfection rate.

Synthesis and characterization of antibacterial drug loaded β-tricalcium phosphate powders for bone engineering applications

Powders of β-tricalcium phosphate [β-TCP, β-Ca₃(PO₄)₂] and composite powders of β-TCP and polyvinyl alcohol (PVA) were synthesized by using wet precipitation methods. First, the conditions for the preparation of single phase β-TCP have been delineated. In the co-precipitation procedure, calcium nitrate and diammonium hydrogen phosphate were used as calcium and phosphorous precursors, respectively. The pH of the system was varied in the range 7-11 by adding designed amounts of ammonia solution. The filtered cakes were desiccated at 80 °C and subsequently calcined at different temperatures in the range between 700-1100 °C. Later on, rifampicin form II was used to produce drug-loaded β-TCP and PVA/β-TCP powders. All the synthesized materials have been characterized from morphological (by scanning electron microscopy) and structural-chemical (by X-ray diffraction and Fourier transform infrared spectroscopy) point of view. The drug loading capacity of the selected pure β-TCP powder has been assessed. The biological performance (cytocompatibility in fibroblast cell culture and antibacterial efficacy against Escherichia coli and Staphylococcus aureus) has been tested with promising results. Application perspectives of the designed drug-bioceramic-polymer blends are advanced and discussed.

Lateral femoral bypass for prosthetic arterial graft infections in the groin

OBJECTIVE

Prosthetic arterial graft infections (PAGIs) in the groin pose significant challenges in terms of revascularization options and risk of limb loss as well as associated morbidities. Although obturator canal bypass (OCB) has been suggested for revascularization of the extremity in these cases, moderate success rates and technical challenges have limited widespread use. Our study analyzed lateral femoral bypass (LFB) as an alternative approach for the treatment of groin PAGIs.

METHODS

This is a retrospective review of a prospectively maintained database of patients who underwent LFB for groin PAGIs at a single center from 2000 to 2017. Patients' data including demographics, comorbidities, perioperative complications, graft patency, and need for reintervention were used. Patients were observed after LFB with duplex ultrasound surveillance in an accredited noninvasive vascular laboratory every 3 months during the first year, followed by every 6 months for the second year and yearly thereafter. After isolation of the infected wound with sterile dressings, remote proximal and distal arterial exposure incisions were made. LFBs were tunneled under the inguinal ligament and lateral to the infected wound from an uninvolved inflow artery or bypass graft to an uninvolved outflow vessel.

RESULTS

A total of 19 LFBs were performed in 16 patients (mean age, 69 ± 12.6 years). Three LFBs were performed urgently for acute bleeding. Choice of conduit included 6 (31.6%) autogenous vein grafts, 10 (52.6%) cadaveric grafts, 2 (10.5%) rifampin-soaked Dacron grafts, and 1 (5.3%) polytetrafluoroethylene graft. Average follow-up was 33 months (range, 0-103 months). Major adverse events occurring within 30 days of the operation included one (5.3%) death and one (5.3%) graft excision for pseudoaneurysm. Primary patency and primary assisted patency at 12 and 24 months were 73% and 83%, respectively. One patient required an amputation 17 months after surgery after failure of repeated revascularization attempts. Overall limb salvage was 93.8% during this follow-up period.

CONCLUSIONS

In this series, LFB for management of groin PAGIs demonstrated higher patency and limb salvage rates compared with previous reports of OCB. Diligent postoperative duplex ultrasound surveillance is critical to the achievement of limb salvage and maintenance of graft patency. These results suggest that LFB, which is technically less complex than OCB, should be considered the first choice for revascularization in select cases of PAGIs involving the groin.

Durable Results with In Situ Graft Repair of Ruptured Salmonella Aneurysm in a Patient with Autoimmune Deficiency Syndrome

We describe a case of a 42-year-old male patient with advanced autoimmune deficiency syndrome (AIDS) (CD4 count of 16 cells/mm3) found to have a ruptured infected infrarenal aortic aneurysm. Emergent in situ repair was performed with a Hemashield Dacron graft (Boston Scientific, Natick, MA). Aortic tissue cultures grew group D Salmonella. Patient was placed initially on intravenous ciprofloxacin followed by lifelong oral levofloxacin and trimethoprim. Over 2 years following repair, he remains asymptomatic, with repair intact and no recurrent infection. This case is the first reported successful long-term repair of a ruptured salmonella infected abdominal aortic aneurysm in the setting of advanced AIDS.

Antibacterial effect of electrospun polycaprolactone/polyethylene oxide/vancomycin nanofiber mat for prevention of periprosthetic infection and biofilm formation

OBJECTIVE

In this study, we developed a biocompatible and biodegradable vancomycin (VM)-eluting electrospun poly(ɛ-caprolactone) (PCL)/polyethylene oxide (PEO)/VM/PCL nanofiber mat. The purpose of this study was to evaluate the efficacy of this nanofiber mat for preventing methicillin-resistant Staphylococcus aureus (MRSA) biofilm on the ossicular prostheses and otitis media.

MATERIALS AND METHODS

Fabrication of VM eluting nanofiber mat was carried out using PCL and PEO. The release of VM was assessed by spectrophotometry in vitro. The antibacterial effect was evaluated by inhibition zone test and biofilm formation test in vitro. And prevention of MRSA infection by guinea pig was assessed by otoendoscopy, temporal bone CT and histopathologic examination in vivo.

RESULTS

VM released followed a triphasic pattern. VM eluting nanofiber mat prevented MRSA biofilm formation on the surface of ossicular prostheses regardless of materials in vitro, and MRSA otitis media in vivo. Otoendoscopy, temporal bone CT, and histopathologic findings revealed well ventilated middle ear.

CONCLUSION

From these results, VM eluting nanofiber mat may be a promising method for prevention of MRSA periprosthetic infection and biofilm formation.

Inadvertent vascular injury of the aorta or vena cava caused by acupuncture

Major visceral vascular injury after acupuncture is a rare but serious complication. We recently treated two patients with an inferior vena cava or an abdominal aorta injury caused by acupuncture. Although both patients underwent successful surgical repair, the highly invasive nature of the operations led to complications, including infection and chyle leakage. Vascular surgeons should be aware that acupuncture can cause serious damage to the vena cava or aorta due to direct injury or subsequent infection.

Sustained release of vancomycin from novel biodegradable nanofiber-loaded vascular prosthetic grafts: in vitro and in vivo study

This study describes novel biodegradable, drug-eluting nanofiber-loaded vascular prosthetic grafts that provide local and sustained delivery of vancomycin to surrounding tissues. Biodegradable nanofibers were prepared by first dissolving poly(D,L)-lactide-co-glycolide and vancomycin in 1,1,1,3,3,3-hexafluoro-2-propanol. The solution was then electrospun into nanofibers onto the surface of vascular prostheses. The in vitro release rates of the pharmaceutical from the nanofiber-loaded prostheses was characterized using an elution method and a high-performance liquid chromatography assay. Experimental results indicated that the drug-eluting prosthetic grafts released high concentrations of vancomycin in vitro (well above the minimum inhibitory concentration) for more than 30 days. In addition, the in vivo release behavior of the drug-eluting grafts implanted in the subcutaneous pocket of rabbits was also documented. The drug-eluting grafts developed in this work have potential applications in assisting the treatment of vascular prosthesis infection and resisting reinfection when an infected graft is to be exchanged.

Contemporary management of infrarenal aortic graft infection: early and late results in 82 patients

Management of aortic graft infection (AGI) remains contentious. The purpose of this study was to evaluate factors of clinical significance which influence the outcome of different treatment modalities for AGI. From 2000 to 2008, 82 consecutive patients were treated for AGI. In situ reconstruction (ISR) was performed in 63 patients with various conduits, extra-anatomic reconstruction (EAR) in 11, conservative treatment in five and resection without reconstruction in three. The perioperative mortality rate for the series (33%) was similar for EAR and ISR and was higher in patients with secondary aortoenteric fistula ( P < 0.001) in those undergoing emergency aortic reconstruction ( P < 0.001) and in AGI caused by virulent organisms ( P < 0.05). Fifteen (27%) of the surviving patients developed a recurrence of infection (RI). EAR patients were more exposed to RI ( P < 0.04). In conclusion, ISR may be more appropriate for AGI, but this study cannot draw a conclusion relating to the optimal conduit for ISR.

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.

Primary infected abdominal aortic aneurysm: surgical procedures, early mortality rates, and a survey of the prevalence of infectious organisms over a 30-year period

PURPOSE

The purpose of this study was to analyze the surgical procedures, culture results, and outcomes, and to survey the prevalence of the infectious organisms over a 30-year period in patients with a primary infected abdominal aortic aneurysm (PIAAA).

METHODS

A total of 11 patients (1.8%) with PIAAA were surgically treated between 1982 and June 2009. All patients had back pain, leukocytosis, and elevated C-reactive protein level. All of the patients underwent either urgent or emergency operations.

RESULTS

Cultures of aortic wall specimens and blood were positive in 10 patients and included Salmonella in 2, Streptococcus in 2, Campylobacter fetus in 2, and Listeria, Haemophilus influenzae, Serratia marcescens, Bacteroides thetaiotaomicron, and an unknown organism in 1 patient each. The 10 patients underwent in situ prosthetic grafting with excision of the infected tissue and lavage using 10 l saline solution; omentum plasty was required in four patients. An axillofemoral bypass was performed in one patient with pus surrounding the AAA. All 10 patients with in situ replacement survived and were administered intravenous antibiotic therapy for 1 month postoperatively. All of these patients left the hospital without any further complications. However, one patient who underwent an axillofemoral bypass died of overwhelming sepsis.

CONCLUSION

In situ replacement with excision of infected tissue, lavage using 10 l saline solution, and omentum plasty for PIAAA successfully resolved the condition. High local concentrations of rifampin-soaked grafts or superficial femoral vein may also be an alternative for an in situ replacement conduit.

Microbial Spectrum and Primary Resistance to Rifampicin in Infectious Complications in Vascular Surgery: Limits to the Use of Rifampicin-Bonded Prosthetic Grafts

There are reports that rifampicin-bonded prosthetic grafts might be a suitable alternative to autologous grafts in vascular graft infections and infectious vascular complications. We characterize the spectrum of microbial agents and susceptibility to antibiotic treatment, especially to rifampicin, in these patients. We carried out a retrospective analysis of wound-swaps and blood cultures in 48 patients with infected prosthetic vascular grafts or primary infectious vascular complications. In 15 of 48 patients (31%), the analysis showed that the microbial organism causing the infection was resistant or not susceptible to rifampicin. Rifampicin-bonded prosthetic grafts should be used with caution in acute infectious complications in vascular surgery, because in about 30% of the cases, the initiating microbial organisms are resistant or not susceptible to rifampicin. Without preoperative confirmation of susceptibility to rifampicin, autologous reconstruction should be preferred.

Efficacy of collagen silver-coated polyester and rifampin-soaked vascular grafts to resist infection from MRSA and Escherichia coli in a dog model

The primary objective of this study was to compare the efficacy of a collagen silver-coated polyester graft, InterGard, with a gelatin-sealed graft, Gelsoft, both soaked in rifampin, for resistance to direct bacterial contamination in an animal model. The second objective was to confirm the lack of inflammation from silver acetate. Vascular grafts, 6 mm in diameter, were implanted in the infrarenal aorta of 28 dogs. Intravenous cefamandole (20 mg/kg) was injected intraoperatively in all dogs. The dogs were divided into three groups. Group I included 12 dogs. Six dogs received silver grafts and six dogs received gelatin-sealed grafts, all soaked with rifampin. Grafts implanted in group I were directly infected with methicillin-resistant Staphylococcus aureus (MRSA). Group II included also six silver grafts and six gelatin-sealed grafts, all soaked with rifampin. Dogs of group II were directly infected with Escherichia coli. Group III comprised four dogs, which received gelatin unsealed grafts, directly infected with MRSA, the control group. All dogs were followed by regular clinical examination, including blood cultures. Grafts in groups I and III and in group II were harvested at 30 days and 10 days, respectively. Bacterial analyses were performed on the explanted grafts. Histology was performed on both the tissue samples and the anastomotic sites of the harvested grafts. In group I, no grafts were infected with MRSA, irrespective of graft type. In group II, no silver grafts were infected with E. coli, whereas one (16.6%) of six gelatin-sealed grafts was infected (p = 0.317). In group III, three (75%) of the four grafts were infected with MRSA. The infection rate in the silver grafts and the gelatin-sealed grafts soaked in rifampin in group I compared with the unsealed gelatin grafts in group III was statistically significantly different (p < 0.05). There was no statistically significant difference in the inflammation score, obtained by histological analysis, between rifampin-soaked silver and Gelsoft grafts in either group I or group II. There were signs of necrosis at the anastomoses in three (25%) gelsoft grafts of 12 in groups I and II. There were no clinical or biological signs of inflammation from use of silver-coated grafts. These results indicate that collagen silver-coated grafts and gelatin-sealed grafts, both soaked in rifampin, provide resistance against MRSA and E. coli. There was a trend toward better resistance but without statistical significance against E. coli from the rifampin silver graft compared with the rifampin-soaked Gelsoft graft, without signs of inflammation from InterGard silver grafts.

Less-invasive and highly effective method for preventing methicillin-resistant Staphylococcus aureus graft infection by local sustained release of vancomycin

OBJECTIVE

Methicillin-resistant Staphylococcus aureus graft infection is one of the most serious complications of vascular surgery. Vancomycin is a potent antibiotic against methicillin-resistant S. aureus; however, systemic administration of vancomycin is not very effective against methicillin-resistant S. aureus graft infection. Therefore, we investigated whether a local sustained release of vancomycin prevents methicillin-resistant S. aureus graft infection.

METHODS

We have developed a poly-L-lactide-co-caprolactone sheet that enabled sustained release of vancomycin for 2 weeks. An expanded polytetrafluoroethylene vascular graft patch (1.5 mm2) was sutured at the anterior wall of the incised murine abdominal aorta. Methicillin-resistant S. aureus (1.0 x 10(3) colony-forming units) was inoculated onto the graft surface. Thereafter, the graft was treated as follows (n = 6 each): no treatment (control group), local injection of an aqueous solution of vancomycin (vancomycin solution group) and local implantation of poly-L-lactide-co-caprolactone containing vancomycin (vancomycin-PLCA group). After 7 days, the graft and blood were sampled and cultured.

RESULTS

The methicillin-resistant S. aureus counts in the grafts of the vancomycin-PLCA group were significantly lower than those of the other groups. Blood cultures of the vancomycin-PLCA group were all negative, whereas those of the other groups were all positive for infection. The survival rate in the vancomycin-PLCA group at 28 days was considerably higher than that in the control group (83.3% vs 16.7%).

CONCLUSIONS

A local sustained-release sheet containing vancomycin reduced methicillin-resistant S. aureus counts in the infected vascular grafts, prevented sepsis, and drastically improved survival rates. This can be used as a highly effective and less-invasive adjunctive treatment method for preventing prosthetic methicillin-resistant S. aureus graft infection.

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.

A systematic review and meta-analysis of treatments for aortic graft infection

OBJECTIVE

We compared pooled estimates of event rates for amputations, conduit failures, reinfections, early mortalities, and late mortalities in patients with aortic graft infection who were treated by extra-anatomic bypass, rifampicin-bonded prostheses, cryopreserved allografts, or autogenous veins.

METHODS

A systematic review was conducted of English language reports in MEDLINE back to 1985 and a meta-analysis was performed on the results. Studies were selected on the basis of medical subject headings aortic, graft, and infection, and also by a standardized and independent quality rating. Inclusion and exclusion criteria were met by 37 clinical studies. Pooled estimates of mean event rates for amputations, conduit failures, reinfections, early (< or =30 day) mortalities, and late (>30 days) mortalities were determined for each treatment modality. Tests of heterogeneity and sensitivity analyses were performed.

RESULTS

Fixed effect analyses, derived after tests of heterogeneity, yielded overall pooled estimates of mean event rates for all outcomes combined of 0.16 for extra-anatomic bypass, 0.07 for rifampicin-bonded prostheses, 0.09 for cryopreserved allografts, and 0.10 for autogenous vein; a lower value signifies fewer overall events associated with the treatment modality. Overall, the robustness of our meta-analysis was demonstrated by the reasonable heterogeneity of pooled data from individual studies (Q statistic <25; P >.1 for all treatment outcomes across all modalities) and the limited variability of outcomes after sensitivity analyses.

CONCLUSION

Although limited by the design of individual published studies whose data were pooled together in this meta-analysis, our results lead to questions concerning whether extra-anatomic bypass should remain the gold standard for treatment of aortic graft infection.

Guidelines for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the UK

These evidence-based guidelines have been produced after a literature review of the treatment and prophylaxis of methicillin-resistant Staphylococcus aureus (MRSA) infection. The guidelines were further informed by antibiotic susceptibility data on MRSA from the UK. Recommendations are given for the treatment of common infections caused by MRSA, elimination of MRSA from carriage sites and prophylaxis of surgical site infection. There are several antibiotics currently available that are suitable for use in the management of this problem and potentially useful new agents are continuing to emerge.

Mycotic Common Iliac Artery Aneurysm Complicating Methicillin-Resistant Staphylococcus aureus Bacteremia: An Unusual Cause of Ureteric Obstruction

A 60-year-old man presented with ureteric obstruction secondary to a mycotic right common iliac artery aneurysm complicating methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. The diagnosis of MRSA was not known at the time of surgery, and in situ replacement of the aneurysm using a rifampicin-bonded prosthesis was performed. The patient made a full recovery, and to date there is no evidence of residual or recurrent infection. To our knowledge, this is the first reported case of mycotic iliac aneurysm infected with MRSA in the literature. We discuss the consequences and the considerable diagnostic and therapeutic problems that arise.

Graft for mycotic thoracic aortic aneurysm: omental wrapping to prevent infection

Nine cases of mycotic thoracic aortic aneurysm were treated surgically between July 1995 and March 2003. The aneurysms were located in the ascending aorta in 1 patient, the descending thoracic aorta in 5, and the thoracoabdominal aorta in 3. Preoperatively, 3 patients were in shock due to rupture of the aneurysm. All patients underwent aneurysmectomy and in-situ graft placement. In 5 patients, the graft was covered with a pedicled omental flap to prevent postoperative graft infection. There were 2 hospital deaths: one patient died of multi-organ failure, and the other died from intrathoracic bleeding. After discharge, one patient died from intrathoracic bleeding 3 months after surgery. These 3 patients had not received omental wrapping. Postoperative graft infection did not occur in the 6 surviving patients during a mean follow-up period of 4.0 +/- 3.1 years. It was concluded that covering the prosthetic graft with a pedicled omental flap may help prevent postoperative graft infection and improve the surgical results.

Inhibition of vascular prosthetic graft infection using a photocrosslinkable chitosan hydrogel

BACKGROUND

Despite improvements in surgical techniques and antimicrobial therapies, prosthetic aortic graft infections remain a clinical problem. It is well known that chitosan has strong antibacterial activities to a wide variety of bacteria including Staphylococcus aureus, epidermidis and Escherichia coli (E. coli). The antibacterial activity by adhering a photocrosslinkable chitosan hydrogel to Dacron grafts was investigated in vitro and in vivo using a rabbit model.

MATERIALS AND METHODS

The photocrosslinkable chitosan hydrogel (50microl) coated grafts (3 x 2mm fragments) were evaluated on a resistance against E. coliin vitro. The graft infections in vivo were also initiated through implantation of a Dacron graft fragment into the infrarenal aorta of a rabbit, followed by a topical inoculation with 10(6) colony-forming units of E. coli. The graft infection was allowed to develop over the following 1 week.

RESULTS

The photocrosslinkable chitosan hydrogel-coated grafts exhibited a resistance against E. coliin vitro. Furthermore, application of 0.1ml photocrosslinkable chitosan hydrogel on the Dacron implant in vivo substantially inhibited graft infection with E. coli.

CONCLUSIONS

These preliminary results suggested the potential use of a photocrosslinkable chitosan hydrogel in directing graft infection prophylaxis.

Methicillin-Resistant Staphylococcus aureus Infections in Vascular Surgery: Increasing Prevalence

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a virulent organism that causes substantial infection-related morbidity and mortality in hospitalized patients. For example, MRSA infection of prosthetic vascular grafts can be limb- and life-threatening in surgical patients. We investigated the incidence of MRSA infection in vascular surgical patients who developed postoperative infectious complications.

METHODS

Prospective data (including procedure, nature of complication, and outcome) were collected on all vascular surgery patients (n = 772) over a two-year period from January, 2000, to December, 2001. The study cohort included all patients who developed postoperative complications (n = 119, 15.4%), including infection, unplanned or prolonged intubation, metabolic abnormalities, and myocardial ischemia. Bacteriologic data of all clinical cultures were reviewed and infection-related outcomes were examined.

RESULTS

Hospital-acquired infection occurred in 79 (66.4%) of 119 patients who developed postoperative complications. Review of microbiology data (total, 197 bacterial isolates) confirmed that gram-positive organisms were the leading cause of infections, with 120 gram-positive isolates (60.9%). Of the gram-positive isolates, S. aureus was the most common pathogen, isolated in 73 (60.8%) cultures. The single most prevalent organism was MRSA, identified in 42 of 73 (57.5%) of cultures. The site of MRSA infection was confirmed to be the surgical site (54.8%), sputum (17.0%), blood (14.3%), urine (9.5%), peritoneal fluid (2.4%), or catheter insertion site (2.4%). Only four patients had prior MRSA infection or colonization. Prosthetic vascular grafts were placed in 51 (42.9%) of the 119 vascular patients, and 26 patients (51.6%) acquired MRSA infection. Graft removal was required in three patients due to infection (MRSA infection in two patients, Pseudomonas aeruginosa in one patient). Forty percent of patients with MRSA infection required an amputation as their surgical procedure. No patient died of MRSA bacteremia during the study period. Mean hospital length of stay (LOS) was longer in patients with MRSA infection (29.6 d vs. 22.7 days, range 2-174 days, p < 0.05) compared to the total study cohort of vascular patients with postoperative infections.

CONCLUSIONS

Methicillin-resistant S. aureus has emerged as the leading cause of postoperative infection in vascular surgery patients, and is associated with substantial morbidity, increased hospital LOS, and higher incidences of amputation and graft removal. Greater emphasis on preoperative screening protocols for MRSA colonization is warranted, in conjunction with aggressive infection control measures, alteration of preoperative prophylactic antimicrobial use in MRSA-colonized patients, and meticulous postoperative surveillance for MRSA infection. Furthermore, antimicrobial treatment of postoperative infectious complications in vascular surgery patients should include empiric coverage for MRSA in institutions where MRSA is endemic.

Use of fascia-peritoneum patch as a pledget for an infected aortic stump

Treatment of aortic prosthetic graft infections remains a challenge. One frequently encountered technical difficulty when removing an infected prosthetic aortic graft is how to close a short, friable remnant aortic stump. We present three case reports in which we used a layer of posterior rectus fascia-peritoneum to bolster oversewing a short infected aortic stump after removal of an infected aortic graft. All three patients underwent staged extra-anatomic axillary-to-femoral artery bypass procedures, with subsequent removal of the infected aortic graft as a second operation. Two of the three procedures were semi-elective, and one was done urgently because of a recurrent aortoenteric fistula. All three patients had less than 1 cm of remaining aortic neck below the renal arteries for closure. In each instance a segment of autogenous posterior rectus fascia-peritoneum was harvested and used as a circumferential pledget to bolster the anastomosis. No patient had stump blowout, and in no case was there computed tomography evidence of aneurysmal enlargement of the stump with follow-up of 12 and 24 months in two of the three survivors. Use of autogenous fascia-peritoneum is a durable and effective method to assist stump closure and prevent stump blowout after removal of infected aortic grafts.

Rifampin and Triclosan but not silver is effective in preventing bacterial infection of vascular dacron graft material

OBJECTIVES

To evaluate the efficacy of silver- or Triclosan-coated prosthetic material compared to Rifampin bonded Dacron concerning their resistance to infection following subcutaneous implantation and contamination with Staphylococcus aureus.

DESIGN

Animal experimental study in mice.

MATERIAL AND METHODS

Thirty-six C3H/HcN mice (Charles River Lab., Sulzfeld, Germany) with a weight between 24 and 27 g were randomised into six groups counting six animals each. Group I: control, gel-sealed dacron graft, group II: gel-sealed dacron graft and local contamination, group III: Intergard-Silver-prosthesis and contamination, group IV: silver/gel-sealed dacron prosthesis (test graft) and contamination, group V: Rifampin-bonded gel-sealed graft and contamination, group VI: Triclosan/collagen-coated dacron graft and contamination. Dacron graft material 0.8x1 cm was subcutaneously implanted in mice. Local contamination with 2x10(7)/0.2 ml S. aureus ATCC 25923 was carried out in groups II to VI. On day 14 the animals were killed and the grafts were explanted. The microscopic, histologic and microbiological evaluation of the graft material and the perigraft tissue was performed.

RESULTS

In control group I no case of infection was detected. In group II, 6 of 6 animals showed infection. In group III (Intergard-Silver) and group IV (silver/gel-test graft) were 6 of 6, in group V (Rifampin) only 1 of 6 grafts and in group VI (Triclosan) 4 of 6 grafts were infected. The difference between the low rate of infection in group V (Rifampin) in comparison to the completely infected groups III and IV (Silver) as well as the control group II was significant. Treatment of grafts with Triclosan could prevent infection only in 1/3 of the cases in group IV.

CONCLUSION

Silver coating failed to prevent graft infection material. A potential antimicrobial property was evident for Triclosan whereas Rifampin-bonded grafts exhibit a significantly reduced infection rate. Thus, silver-coated vascular grafts cannot ensure protection from vascular graft infection.

In situ revascularization with silver-coated polyester grafts to treat aortic infection: early and midterm results

PURPOSE

In this prospective study we analyzed the immediate and midterm outcome in patients with abdominal aorta infection (mycotic aneurysm, prosthetic graft infection) managed by excision of the aneurysm or the infected vascular prosthesis and in situ replacement with a silver-coated polyester prosthesis.

METHODS

From January 2000 to December 2001, 27 consecutive patients (25 men, 2 women; mean age, 69 years) with an abdominal aortic infection were entered in the study at seven participating centers. Infection was managed with either total (n = 18) or partial (n = 6) excision of the infected aorta and in situ reconstruction with an InterGard Silver (IGS) collagen and silver acetate-coated polyester graft. Assessment of outcome was based on survival, limb salvage, persistent or recurrent infection, and prosthetic graft patency.

RESULTS

Twenty-four patients had prosthetic graft infections, graft-duodenal fistula in 12 and graft-colonic fistula in 1; and the remaining 3 patients had primary aortic infections. Most organisms cultured were of low virulence. The IGS prosthesis was placed emergently in 11 patients (41%). Mean follow-up was 16.5 months (range, 3-30 months). Perioperative mortality was 15%; all four patients who died had a prosthetic graft infection. Actuarial survival at 24 months was 85%. No major amputations were noted in this series. Recurrent infection developed in only one patient (3.7%). Postoperative antibiotic therapy did not exceed 3 months, except in one patient. No incidence of prosthetic graft thrombosis was noted during follow-up.

CONCLUSION

Preliminary results in this small series demonstrate favorable outcome with IGS grafts used to treat infection in abdominal aortic grafts and aneurysms caused by organisms with low virulence. Larger series and longer follow-up will be required to compare the role of IGS grafts with other treatment options in infected fields.

Graft-preserving treatment for vascular graft infected with Staphylococcus aureus with antibiotic-releasing porous apatite ceramic in the rabbit

OBJECTIVE

This study was undertaken to investigate whether infection of a vascular graft with Staphylococcus aureus can be treated in situ by applying antibiotic-loaded porous apatite ceramic, in a rabbit model.

METHODS

Teicoplanin (TEIC) was loaded onto a beta-tricalcium phosphate (TCP) block, a type of porous apatite ceramic. The activity of TEIC released from the antibiotic-loaded TCP block was examined in vivo. A vascular graft was patched onto the abdominal aorta in 24 rabbits, and S aureus was applied directly on it. Seven days postoperatively, each rabbit underwent repeat laparotomy, and retroperitoneal abscess around the prosthetic vascular patch was debrided. Animals were divided into four groups of 6 rabbits each. In group 1 only debridement was carried out. In groups 2 and 3, solution containing 40 or 60 mg of TEIC, respectively, was applied to the prosthetic vascular patch. In group 4, an antibiotic-loaded TCP block (63 +/- 6.6 mg of TEIC) was placed around the graft. Three weeks after the second operation, the graft, the tissue around it, and arterial blood were collected and cultured.

RESULTS

TEIC activity was maintained for 28 days in vivo. In group 1, bacterial cultures of the prosthetic vascular graft and the tissue around it were positive in 5 animals and negative in 1 animal (infection rate, 83%). In both groups 2 and 3, cultures were positive in 3 animals and negative in 3 animals (infection rate, 50%). In group 4, cultures were negative in all animals (infection rate, 0%). Blood cultures were negative in all animals. Infection rate in group 4 was significantly lower than that in group 1 (P =.03), and was also lower than that in groups 2 and 3, but the difference was not significant.

CONCLUSIONS

Use of slow-release antibiotic loaded onto a TCP block, along with debridement, may control infection in vascular grafts in situ, averting the necessity to remove the graft.