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ABSTRACT: The purpose of this study was to treat an established prosthetic vascular graft infection by in situ replacement with a rifampin-bonded gelatin-sealed Dacron graft in an animal model.
The infrarenal aorta of 18 dogs was replaced with a gelatin-sealed graft contaminated in vitro by soaking it in a solution with Staphylococcus epidermidis. One week later, animals were randomized into three groups. In group I (control, (n = 6), the dogs did not undergo repeat operations. The dogs in groups II and III underwent repeat operation. In these animals the infected grafts were removed for bacteriologic analysis and replaced in situ with one of two types of grafts: group II (n = 6) received an untreated, gelatin-sealed graft; group III (n = 6) received a rifampin-bonded, gelatin-sealed graft. Antibiotic bonding was obtained by soaking grafts for 15 minutes in a 60 mg/ml saline solution of rifampin at 37 degrees C. All 18 dogs received no systemic adjunct antibiotic therapy. Control grafts and replacement grafts were removed 4 weeks after the initial implantation for bacteriologic analysis. When harvested, all the grafts were cut into two fragments, and quantitative bacterial cultures were obtained from all the fragments. Results were expressed as colony-forming units (CFU)/cm2 of graft material.
All 18 initially implanted grafts and all the untreated replacement grafts were grossly infected at the time of removal, whereas all the rifampin-bonded replacement grafts had normal incorporation. None of the rifampin-bonded grafts grew bacteria, whereas all the initially implanted and all the untreated replacement grafts were infected (p < 0.01). Bacterial counts from the infected fragments were similar in control grafts (2.6 +/- 1.9 x 10(6) CFU/cm2), in initially implanted grafts of groups II (9 +/- 1.1 x 10(5) CFU/cm2) and III (1.3 +/- 1.5 x 10(6) CFU/cm2), and in untreated replacement grafts of group II (1.7 +/- 2.5 x 10(6) CFU/cm2). Blood culture results and culture results of liver, spleen, kidney, and lung specimens at the time of sacrifice were negative.
This study demonstrates that rifampin-bonded gelatin-sealed Dacron grafts are resistant to infection when used for in situ replacement of an infected graft in the dog.
Journal of Vascular Surgery 04/1994; 19(4):739-41. · 3.21 Impact Factor
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ABSTRACT: Possible mechanisms of the prophylactic effect of ceftriaxone against late bacteremic vascular graft infection in dogs were investigated. Dogs bearing an expanded polytetrafluoroethylene graft implanted as thoracoabdominal aortic bypass for one month were exposed to transient bacteremia produced by intravenous injection of 2.6 +/- 1.8 x 10(8) colony forming units Staphylococcus aureus 209P-R. To assess the effect of the antibiotic on bacteria already adherent onto the grafts, we compared the results from six untreated dogs used as controls and six dogs receiving ceftriaxone (0.5 g, intramuscularly) 90 minutes after the bacteremic challenge. The grafts were removed one week after the bacteremic challenge and cut into 10 to 15 fragments, each submitted to viable bacterial counts. The number of grafts and the number of fragments yielding bacterial growth were the same in the two groups. However, the median density of bacteria was lower (p less than 0.01) in the dogs given ceftriaxone, 64 colony forming units/cm (range: 3-8,700), than in the control dogs, 585 colony forming units/cm (range: 12-64,000), suggesting that ceftriaxone had an effect on the postadherence phase of the development of infection. To assess the effect of ceftriaxone on the adherence phase we compared the results from seven untreated dogs and seven dogs receiving ceftriaxone (0.5 g intramuscularly) 90 minutes before the bacteremic challenge. The grafts were removed two hours after the bacteremic challenge. Though all the seven grafts were colonized in each group, the number of fragments yielding bacterial growth was lower (p less than 0.05) in the dogs given ceftriaxone (59/70) than in the control dogs (90/91).(ABSTRACT TRUNCATED AT 250 WORDS)
Annals of Vascular Surgery 12/1991; 5(6):500-5. · 1.03 Impact Factor
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ABSTRACT: This study examines the efficacy of rifampin bonding to a gelatin-sealed knitted Dacron graft to prevent perioperative bacteremic vascular graft infection. Antibiotic bonding was obtained by soaking grafts for 15 minutes in a 1 mg/ml saline solution of rifampin at 37 degrees C. Nineteen dogs had thoracoabdominal aortic bypass: seven (group I) received a rifampin treated graft; six (group II) received an untreated gelatin-coated graft; and six (group III) received an uncoated Dacron graft. Two days later bacteremic challenge was produced by rapid intravenous injection of 5 x 10(5) colony forming units of methicillin resistant Staphylococcus aureus. Grafts were harvested five days after this challenge and cut into 10 fragments, each submitted to bacterial counts. Results were expressed as CFU/cm2 of graft material. In group I, no graft was infected, whereas all grafts in groups II and III were infected (p less than 0.05). Median bacterial counts from the infected fragments (median +/- SD) were similar in groups II (2.5 x 10(5) CFU/cm2) and III (4 x 10(4) CFU/cm2). Blood cultures at time of sacrifice were negative in all dogs in group I and positive in five of six dogs in groups II and III. Cultures of liver, spleen, kidney, and lung specimens were always negative in group I and positive in 22 of 24 specimens in group II and 23 of 24 specimens in group III. Soaking a gelatin-sealed Dacron graft in rifampin solution evidently prevents early bacteremic graft infection and secondary foci of infection in this model.
Annals of Vascular Surgery 10/1991; 5(5):408-12. · 1.03 Impact Factor
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ABSTRACT: This study was undertaken to determine the efficacy of a single-dose antibiotic injection to prevent late bacteremic vascular graft infection. Twelve dogs had thoracoabdominal aortic bypass with expanded polytetrafluoroethylene grafts. One month later, a bacteremic challenge was produced by rapid intravenous injection of 5 x 10(8) Staphylococcus aureus. Dogs were treated by pairs, each dog of a pair being randomly assigned to receive either 0.5 g ceftriaxone (group I, n = 6) or saline (group II, n = 6), intramuscularly, 90 minutes before challenge. Grafts were harvested seven days after bacteremic challenge. They were cut into 10 fragments, each of which were submitted to bacterial counts. Results of bacterial counts were expressed as colony forming units per square centimeter of graft segment. The overall infection rates were zero of six grafts in group I and four of six in group II (p less than 0.05). In group I, none of the 60 graft fragments were found to be culture positive (p greater than 0.01). Bacterial counts from the 24 infected fragments were highly variable, ranging from 12 colony forming units/cm2 to 64 x 10(3) colony forming units/cm2. Serial quantitative blood cultures revealed a similar decrease of bacteremia in both groups with 2.4 +/- 0.9 x 10(2) (group I) and 1.2 +/- 0.9 x 10(2) (group II) colony forming units/ml at three hours. Mean ceftriaxone serum level was 26 +/- 18 mg/L at the time of bacteremic challenge. These data suggest that a single dose of ceftriaxone given before bacteremic challenge is sufficient to prevent late bacteremic vascular graft infection in this model.(ABSTRACT TRUNCATED AT 250 WORDS)
Annals of Vascular Surgery 12/1990; 4(6):528-32. · 1.03 Impact Factor
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ABSTRACT: Colonization of a polyester (Dacron) vascular graft by Staphylococcus aureus 209P-R was studied. Twenty-five dogs had thoracoabdominal aortic bypass. After intervals of 2 hours (three dogs), 8 days (five dogs), 1 month (six dogs), 2 months (six dogs), or 6 months (five dogs), a bacteremic challenge was produced by intravenous injection of 6 x 10(8) colony-forming units of S. aureus. Two hours later grafts were removed and cut into 10 fragments, each submitted to bacterial counts and scanning electron microscopic studies. Results of bacterial counts were expressed in colony-forming units (CFU) per square centimeter of graft segment (median [lower to upper quartiles]). Normal canine aortas (n = 2) used as controls trapped no bacteria. Colonization of Dacron grafts varied according to the duration of graft function (p less than 0.01): after 2 hours, 4416.5 CFU (1158 to 9073 CFU); after 8 days, 1515 CFU (963 to 2893 CFU); after 1 month, 199 CFU (86 to 538 CFU); after 2 months, 615 CFU (243 to 1407 CFU); and after 6 months, 1 CFU (1 to 5 CFU). Heavily colonized fragments were observed for duration of graft function of 2 months or less, whereas at 6 months all the fragments trapped fewer than 50 CFU/cm2 of graft segment. Scanning electron microscopy showed that colonization was closely associated with healing. Staphylococcal entrapment was related to the amount of fibrin deposits, which were especially abundant where the thrombotic matrix was unorganized and on bare polyester filaments. Graft colonization is especially to be feared in the first weeks after graft implantation, an observation which may help to define guidelines for preventing hematogenous vascular graft infection.
Journal of Vascular Surgery 08/1988; 8(1):1-9. · 3.21 Impact Factor
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ABSTRACT: We developed an animal model to reproduce hematogenous seeding of vascular grafts with Staphylococcus aureus. Expanded polytetrafluoroethylene (ePTFE) grafts were implanted in 41 dogs as thoracoabdominal aortic bypasses for six durations of implantation between 2 hours and 6 months. The inoculum containing an average of 10(8) viable bacteria/ml was then injected intravenously in 1 minute. Normal dog aortas were used as controls. They entrapped very few bacteria (0.7 +/- 1.7 colony-forming unit [CFU]/cm2). Colonization of ePTFE grafts was maximal after 2 hours of implantation (589 +/- 733 CFU/cm2). Bacterial entrapment decreased after 2 days (225 +/- 315 CFU/cm2, p less than 0.001) and 8 days (70 +/- 115 CFU/cm2, p less than 0.001) of implantation, but it was similar after 8 days, 1 month (83 +/- 90 CFU/cm2), or 6 months (93 +/- 143 CFU/cm2) of implantation. Colonization of ePTFE measured after 2 months of implantation (371 +/- 591 CFU/cm2) was significantly higher (p less than 0.001) than after 1 or 6 months of implantation. More than 500 CFU/cm2 were seen in 37% of the prosthetic fragments tested after 2 hours of exposure to blood; 99% of the fragments tested after 6 months of implantation trapped less than 500 CFU/cm2. Scanning electron microscopy showed that staphylococci were mostly seen on native fibrin deposits, particularly after 2 hours and 2 months of implantation. That persistent susceptibility of a flow surface devoid of endothelium to hematogenous bacterial colonization has to be taken into account to prevent delayed graft infections. Furthermore, it would be important to compare the ePTFE with other types of grafts whose healing phenomena are different.
Journal of Vascular Surgery 06/1987; 5(5):743-8. · 3.21 Impact Factor
