In vitro antistaphylococcal activity of collagen-sealed Dacron vascular prostheses bonded with rifampin, vancomycin, or amikacin

Conventional or Endovascular Treatment of Ongoing Mycotic Aortic Aneurysmal Disease?

We report a case in which conventional and endovascular exclusion techniques were used to treat ongoing mycotic aortic aneurysmal disease. A 51-year-old man presented with an infrarenal mycotic aortic aneurysm that was excluded and reconstructed with a superficial femoral vein. Two years later, he developed a symptomatic mycotic aneurysm of the descending thoracic aorta, which required emergent treatment with a stent graft. The patient died 5 months later of massive bleeding owing to an aortobronchial fistula deriving from a new thoracic aneurysm proximal to the stent graft. Choices and different modes of treatment are discussed. Endovascular treatment of symptomatic mycotic aortic aneurysm might provide a valid alternative to open repair but may be unsuccessful owing to ongoing infection. In situ replacement using autologous material seems appealing whenever feasible.

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.

Cyanoacrylate adhesive provides efficient local drug delivery

Biodegradable drug delivery systems have advanced treatment of a wide spectrum of musculoskeletal problems. However, their lack of availability and cost can restrict use. To find an easily available and inexpensive biodegradable implant, we tested a widely used tissue adhesive, n-butyl-2-cyanoacrylate, as a drug-trapping material. We tested vancomycin with commercially available absorbable gelatin-sponge pieces as the scaffold. We evaluated the in vitro and in vivo drug release profiles and in vivo inflammatory response. A mouse muscle pouch model was used for in vivo evaluations. The released vancomycin level was measured by fluorescence polarization immunoassay technique, and a leukocyte count-based grading system was used to evaluate inflammatory response. Our findings suggest the proposed implant provides effective drug release for as much as 42 days in vitro and 14 days in vivo. The presence of n-butyl-2-cyanoacrylate led to a local inflammatory response which decreased after 3 weeks in the group with less adhesive. These results showed that n-butyl-2-cyanoacrylate could efficiently trap and slowly release a drug when used in the structure of a biodegradable local drug delivery device.

An In Vitro Model to Compare the Antimicrobial Activity of Silver-Coated Versus Rifampicin-Soaked Vascular Grafts

In situ replacement of infected vascular grafts is an accepted alternative to total graft excision and extraanatomic replacement. Its success relies upon the ability of the newly inserted graft to resist recurrent infection. This study compares the efficacy of two methods used to reduce the risk of graft reinfection: rifampicin soaking versus silver bonding of grafts. The grafts' resistance to infection was tested in vitro in two protocols, each using a panel of seven common bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The length of time the grafts remained free of organisms was compared between the groups. Both the silver graft and the rifampicin-soaked graft were significantly better than control graft at preventing bacterial growth on the graft surface. The rifampicin inhibited the growth of the gram-positive organisms, including MRSA, significantly better than the silver graft on days 2 and 3 (p < 0.001). Conversely, the silver graft was significantly more effective against the gram-negative organisms until day 4 (p < 0.0001). Both types of graft inhibit the in vitro growth of bacteria more effectively than controls, with rifampicin being most effective against gram-positive organisms and silver being best against the gram-negative organisms.

Impregnated polyester arterial prostheses: performance and prospects

Impregnated polyester arterial prostheses have gained wide acceptance by most vascular surgery teams, probably because these prostheses are easy to use, without any preclotting. We offer here a synthesis of the main studies that have appraised the experimental and clinical performance of these prostheses, and we delineate their major prospects.

In situ repair of mycotic abdominal aortic aneurysms with rifampin-bonded gelatin-impregnated Dacron grafts: a preliminary case report

Treatment of mycotic aortic aneurysm by excision and extraanatomic bypass is difficult to apply when the infectious process involves the visceral arteries. On the basis of experimental studies in our laboratory that demonstrated prolonged antistaphylococcal activity of rifampin-bonded, gelatin-impregnated Dacron grafts after implantation in the arterial circulation, this conduit was successfully used for in situ replacement of a native aortic infection in two patients. Both patients had fever, leukocytosis, abdominal or back pain, and a computed tomographic scan that demonstrated contained rupture of a mycotic aneurysm. Preoperative computed tomography-guided aspiration and culture of periaortic fluid from one patient grew Staphylococcus aureus. Treatment consisted of prolonged (6 weeks) culture-specific parenteral antibiotic therapy, excision of involved aorta, oxychlorosene irrigation of the aortic bed, and restoration of aortic continuity by in situ prosthetic replacement. A preliminary right axillobifemoral bypass was performed in the patient who had an infection involving the suprarenal and infrarenal aorta. In both patients intraoperative culture of aorta wall recovered S. aureus. Patients were discharged at 20 and 21 days. Clinical follow-up and computed tomographic imaging of the replacement graft beyond 10 months after surgery demonstrated no signs of residual aortic infection. In the absence of gross pus and frank sepsis, the use of an antibiotic-bonded prosthetic graft with antistaphylococcal activity should be considered in patients who have arterial infections caused by S. aureus when excision and ex situ bypass are not feasible.