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.     

Experimental study of antiseptic (tauroline, taurolidine) and antibiotic (sulmycin implant) drugs in vascular prosthesis infections in a standardized infection model

It was the aim to examine whether local application of antiseptic and antibiotic substances is an effective treatment of vascular graft infection. MATERIAL AND METHODS: 19 pigs with a bodyweight between 20 and 30 kg were assigned to three different groups. Group I: control (6), group II: local treatment with Sulmycin implant, group (6) III: local treatment with Taurolin (Taurolidine) (7). An unprotected vascular graft was inserted in the right femoral artery of all pigs. After finishing the proximal and distal anastomosis and prior to closure of the incision, the vascular grafts were contaminated locally with 2 x 10(7) CFU/ml Staphylococcus aureus ATCC 29213. Seven days later all animals received another unprotected vascular prosthesis with or without additional treatment according to groups I, II, III. 28 days after primary operation the animals were euthanized and the grafts harvested. The specimens were examined for signs of infection by histology and microbiology. RESULTS: After the primary operation all animals presented with infected vascular prosthesis. At termination of the trial on day 28 all grafts of group I were contaminated, 5 out of 6 grafts in group II, and 5 out of 7 in group III presented with infected grafts. There was no significant statistical difference between the groups. Infection could not be prevented by the antimicrobial agents used. The primary infecting organism Staphylococcus aureus, however, was eliminated in all cases. CONCLUSIONS: Both antimicrobial substances examined were not effective in the treatment of vascular graft infection, but might be used as adjuvant therapy of vascular graft infection, whereby Sulmycin implant seems to be more effective regarding the incorporation of the prosthesis.     

Efficacy of vancomycin, teicoplanin and fusidic acid as prophylactic agents in prevention of vascular graft infection: an experimental study in rat.

OBJECTIVES: To compare the efficacy of a single prophylactic dose of intra-peritoneal vancomycin and teicoplanin with anti-biotic treated Dacron grafts (vancomycin, teicoplanin, 10 or 40% fusidic acid-soaked grafts) in preventing vascular graft infections in a rat model. DESIGN: Prospective, randomized, controlled animal study. MATERIALS AND METHODS: The graft infections were established in the subcutaneous tissues of 80 female Sprague-Dawley rats by the implantation of Dacron prostheses followed by the topical inoculation with methicillin-resistant Staphylococcus aureus. The study groups were as follows: (1) uncontaminated control group, (2) untreated contaminated group, (3) contaminated group with intra-peritoneal vancomycin, (4) contaminated group with intra-peritoneal teicoplanin, (5) contaminated group received vancomycin-soaked Dacron graft, (6) contaminated group received teicoplanin-soaked Dacron graft, (7) contaminated group received 40% fusidic acid-soaked Dacron graft, and (8) contaminated group received 10% fusidic acid-soaked Dacron graft prophylaxis. The grafts were removed after 7 days and evaluated by a quantitative culture analysis. RESULTS: No infection was detected in controls. The untreated contaminated group had a high bacteria count (6.0 x 10(4) CFU/cm2 Dacron graft). Groups that received intra-peritoneal vancomycin or teicoplanin had less bacterial growth (4.8 x 10(3) and 3.9 x 10(3)CFU/cm2 Dacron graft, respectively). Similarly, the group that received 10% fusidic acid-soaked graft showed less bacterial growth (3.6 x 10(3) CFU/cm2 Dacron graft). The groups with vancomycin-, teicoplanin- and 40% fusidic acid-soaked grafts showed no evidence of infection. Statistical analyses demonstrated that intra-peritoneal prophylactic antibiotic treatment was less effective in inhibiting bacterial growth than high concentration antimicrobial-soaking of grafts. CONCLUSION: The use of vancomycin-, teicoplanin- and 40% fusidic acid-soaked grafts was effective in preventing primary prosthetic vascular graft infection.     

The prophylactic efficacy of rifampicin-soaked graft in combination with systemic vancomycin in the prevention of prosthetic vascular graft infection: an experimental study

OBJECTIVE: To investigate the prophylactic efficacy of systemic, topical, or combined antibiotic usage in the prevention of late prosthetic vascular graft infection caused by methicillin-resistant Staphylococcus epidermidis (MRSE) and the differential adherence of S. epidermidis to Dacron and ePTFE grafts in a rat model. MATERIALS AND METHODS: Graft infections were established in the back subcutaneous tissue of 120 adult male Wistar rats by implantation of 1-cm(2) Dacron/ePTFE prosthesis followed by topical inoculation with 2 x 10(7) CFU of clinical isolate of MRSE. Each of the series included one group with no graft contamination and no antibiotic prophylaxis (uncontaminated control), one contaminated group that did not receive any antibiotic prophylaxis (untreated control), one contaminated group in which perioperative intraperitoneal prophylaxis with vancomycin (10 mg/kg) was administered, two contaminated groups that received rifampicin-soaked (5 mg/1 ml) or vancomycin-soaked (1 mg/1 ml) grafts, and one contaminated group that received a combination of rifampicin-soaked (5 mg/1 ml) graft with perioperative intraperitoneal vancomycin prophylaxis (10 mg/kg). The grafts were removed sterilely 7 days after implantation and evaluated by using sonication and quantitative blood agar culture. RESULTS: MRSE had significantly greater adherence to Dacron than ePTFE grafts in the untreated contaminated groups (P < 0.001). Rifampicin had better efficacy than vancomycin in topical application, but the difference was not statistically significant (P > 0.05). Intraperitoneal vancomycin showed a significantly higher efficacy than topical vancomycin or rifampicin (P < 0.001). The best results were provided by a combination of intraperitoneal vancomycin in rifampicin-soaked graft groups (P < 0.001). CONCLUSIONS: The combination of rifampicin and intraperitoneal vancomycin seems to be the best choice for the prophylaxis of late prosthetic vascular graft infections caused by MRSE.     

Titanium-coated silicone is not effective for preventing graft infection

AIM: Titanium-coated grafts for breast augmentation are available since 2001 and are used clinically. The titan surface is supposed to improve the tissue compatibility and to lower the infection rate. It was the aim of the present study to validate the antibacterial efficiency of titanium-coated silicone. MATERIAL AND METHODS: C3H/HcN mice were assigned to four different groups (n=6/group). Silicone without (group I and III) or with (group II and IV) titanium were implanted subcutaneously. Following this in groups III and IV a local contamination was induced with 2 x 10 (7) CFU/0.1 ml Staphylococcus aureus ATCC 25923. Groups I and II were not infected. 14 days after primary operation all animals were euthanized and the grafts harvested. Specimens were examined for signs of infections by macroscopy, histology and microbiology. RESULTS: In group I none of the grafts were infected (0/5). In group II (silicone, + titanium, no contamination) one infection was evident due to biting of the animal (1/6). In group III (silicone, no titanium, contamination) an infection was detected in all mice (6/6). The use of titanium, however, did not significantly reduce the infection rate in contaminated animals (group IV, 5/6). Interestingly, tissue integration of titanium-coated grafts was macroscopically reduced compared to non- titanium-coated grafts (group II vs. I). CONCLUSION: The titanium-coated silicone grafts were not effective in protecting infection in vivo. The decreased tissue integration of titanium-coated grafts, however, might reduce the rate of capsular contracture. This potential advantage of titanium needs to be validated in controlled clinical trials.     

Stent graft repair of visceral artery aneurysms

PURPOSE: The purpose of this study was to compare the efficacy of rifampin-bonded gelatin-sealed and silver acetate/collagen-coated knitted polyester prostheses for the prevention of bacteremic graft infection in an animal model. METHODS: Eighteen 6.0-mm polyester grafts (length, 5.0 cm) were implanted in dogs end-to-end into the infrarenal aorta. The dogs were divided into four groups as a function of type of prosthesis implanted. The dogs in groups I (n = 3) and II (n = 3) received control gelatin-sealed or collagen-coated polyester prostheses, respectively. In group III (n = 6), the dogs received rifampin-bonded gelatin-sealed polyester prostheses. In group IV (n = 6), the dogs received silver/collagen-coated polyester prostheses. Two days after implantation, the grafts were challenged with 6 x 10(9) Staphylococcus aureus intravenously. One week after implantation, the 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 graft material. Bacteriologic study was also performed on various tissue samples. The chi(2) test was used to compare the culture proven infection of control and antimicrobial grafts. RESULTS: All the control grafts were infected with S aureus at the time of removal. Five of the six silver/collagen-coated grafts were infected, whereas none of the six rifampin-bonded gelatin-sealed grafts grew S aureus (P <.01). There was no significant difference in the number of positive culture results of organ samples between the different groups of dogs. CONCLUSION: These results indicate that rifampin-bonded gelatin-sealed polyester grafts are significantly more resistant to bacteremic infection than are silver/collagen-coated polyester grafts in a highly challenging model.     

Establishment of a vascular graft infection model in the sheep carotid artery

A study was performed to assess whether a model of vascular graft infection could be established in sheep carotid artery. Either a protein sealed Dacron or a polytetrafluoroethylene (PTFE) graft was used in 22 sheep while a control operation was performed on 4 animals. Staphylococcus aureus in concentrations of 10(2), 10(4), 10(6) or 10(8) colony-forming units (CFU) was inoculated into the wound before closure. No infection occurred with an inoculum of 10(2). The lowest concentration of organism producing infection was 10(4) for PTFE, 10(6) for Dacron and 10(8) for controls. Six of eleven Dacron grafts and seven of ten PTFE grafts became infected. The sheep carotid artery has proven a satisfactory model for studies of vascular graft infection.     

A passive system using rifampin to create an infection-resistant vascular prosthesis

Vascular prosthesis infection is a devastating complication of vascular operations. The development of a simple process for imparting infection resistance to vascular prosthesis material would be invaluable. Rifampin was added to the blood that was used to preclot 8 mm Dacron vascular prostheses that were used to replace the infrarenal aorta in 10 mongrel dogs. Rings of the grafts were resected after blood had flowed through them for 0 minute, 15 minutes, 60 minutes, and 24 hours. The resected graft rings were placed on culture plates that had been inoculated heavily with Staphylococcus aureus. The rate of antibiotic dialysis from the graft was determined by comparison of the inhibition rings that were produced by the graft rings at each subsequent interval. At 60 minutes, inhibition was 94% of that at time 0. Inhibition at 24 hours was 91%, which demonstrated no significant decrease from 60 minutes. Other antibiotics were screened by this technique, but none of them demonstrated inhibition at 24 hours. In a pilot study in which two dogs were given parenteral rifampin before and after operation and grafts were preclotted with blood that contained rifampin, it was suggested that there was a slight increase in inhibition at 24 hours (93%). The data indicated that rifampin that is added to the blood that is used to preclot a porous Dacron prosthesis is so slowly dialyzed from the graft that inhibition remains at 24 hours. This passive system imparts potential resistance to the prosthesis.     

Experimental colonization of a polyester vascular graft with Staphylococcus aureus: a quantitative and morphologic study

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.     

Bacterial resistance of refrigerated and cryopreserved aortic allografts in an experimental virulent infection model

PURPOSE: The bacterial resistance of refrigerated and cryopreserved aortic allografts in a highly virulent infection in a dog model was studied. METHODS: The infrarenal aorta of 12 dogs was replaced with either a cryopreserved aortic allograft (group I, n = 6) or a refrigerated aortic allograft (group II, n = 6) in infected sites. Allografts were harvested from dogs and stored for 1 week, either by cryopreservation (-140 degrees C) or refrigerated method (4 degrees C), in a preservation medium. At the time of implantation, induction of infection was achieved with an infected piece of knitted Dacron placed just beneath the allograft. The Dacron was contaminated in vitro by soaking it in a solution with Staphylococcus aureus PR209. All 12 dogs received no adjunct antibiotic or antithrombotic therapy. Four weeks after implantation, the animals were killed to recover the grafts for bacteriological and histological analyses. Bacterial results were expressed as colony-forming units (CFU)/cm2 of graft material. RESULTS: In group I, only one allograft grew bacteria at 2. 16 x 10(6 )CFU/cm2, with a blood culture positive for S aureus. In group II, one dog died at 3 weeks from a false septic aneurysm rupture, all the allografts were infected (P <.05) with a mean bacterial count of 9.41 +/- 6.8 x 10(4) CFU/cm2, and three blood cultures were positive for S aureus. The patency of the grafts was analyzed at the time of recovery. Three laminar thrombi without occlusion were present in group I; none were present in group II. A better preserved endothelium in group I was revealed by means of histologic analysis staining with factor VIII antibody before implantation. After 4 weeks of implantation in the infected site, infected allografts presented polynuclear infiltrates in the media with a high degree of inflammatory reaction, and endothelial recovery was more significant in group I, with numerous young plump cells. CONCLUSION: This study demonstrates that cryopreserved allografts implanted in infected sites in a dog model can produce greater bacterial resistance.     

The prevention and treatment of vascular graft infection with a Triclosan (Irgasan)-bonded Dacron graft: an experimental study in the pig.

Objectives: to evaluate the role of Triclosan (Irgasan(R)) in the prevention of prosthetic graft infection. Material and methods: fifty-one pigs were assigned randomly to six groups. Group I (graft) and II (graft and Triclosan) were control groups. Groups III (graft) and IV (grafts and Triclosan) were contaminated with 2 x 10(7)CFU/ml S. aureus. Groups V (graft) and VI (graft and Triclosan) were intraoperatively contaminated with 2 x 10(7)CFU/ml S. aureus and reoperated on after 7 days. Remaining animals were sacrificed on day 28. The end point of the investigation was vascular graft infection, defined as the bacteriological and/or histological proof of infection. Results in both control groups no vascular graft infections were detected in Groups I and II. All of the group III animals presented but none of the group IV developed a graft infection (p <0.02). All of the group V animals presented and 10 of 12 animals developed a graft infection. Conclusion: in this animal model Triclosan bonding appears effective in preventing prosthetic graft infection. However, the in situ replacement of Triclosan-protected grafts was not successful in the treatment of graft infection.     

Prevention of graft infection by use of prostheses bonded with a rifampin/collagen release system.

The objective of this study was to test the efficacy of bonding rifampin to double-velour Dacron grafts with collagen to prevent graft sepsis. Fifty 6.0 mm Dacron grafts (length 5.0 cm) impregnated with either collagen (control) or collagen plus rifampin (experimental) were implanted in dogs end-to-end into the infrarenal aorta. The dogs were divided into four groups (each with an experimental and control subdivision) as a function of time between grafting and bacterial challenge. At 2, 7, 10, or 12 days after graft implantation, sequential groups were challenged with 1.2 x 10(8) colony forming units of Staphylococcus aureus (clinical isolate) intravenously suspended in 250 ml normal saline. Three weeks after hematogenous seeding, the grafts were sterilely harvested. One-tailed Fisher's exact test was used to compare the patency and culture-proven infection of control and antibiotic coated grafts as a function of implantation time before bacteremic challenge. In the 2-day group, four of six control grafts were infected compared with zero of six experimental grafts (p less than 0.030). In the 7-day group, five of six control grafts were infected with S. aureus versus zero of six in the experimental group (p less than 0.008). In the 10-day group, one of six experimental grafts was infected, but the control group had only two of six graft infections. In the 12-day group two of six experimental grafts and one of five control grafts were infected. These results indicate that rifampin bonded with collagen to knitted Dacron grafts will protect the graft from bacteremic infection for 7 days after implantation in a highly challenging model.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of an antibiotic-bonded graft for in situ reconstruction after prosthetic graft infections.

We have developed an infection resistant vascular prosthesis by bonding rifampin to Dacron grafts with the use of a collagen matrix release system. The purpose of this study was to determine the efficacy of this antibiotic-bonded graft in resisting infection after an in situ reconstruction of a previously infected prosthetic bypass. Eighty-three adult mongrel dogs underwent implantation of a 3 cm untreated Dacron graft into the infrarenal aorta. This initial graft was deliberately infected, at the time of operation, with 10(2) organisms of Staphylococcus aureus by direct inoculation. One week later, the dogs were reexplored, the retroperitoneum debrided, and the animals randomized to undergo an end-to-end in situ graft replacement with either one of two types of prosthetic grafts: group I (collagen, n = 36) received control collagen-impregnated knitted Dacron grafts; group II (rifampin, n = 47) received experimental collagen-rifampin-bonded Dacron grafts. Each group of animals was then subdivided to receive one of four treatment protocols: (a) no antibiotic therapy, (b) cephalosporin peritoneal irrigation solution (cefazolin 500 mg/1000 ml) during operation and two doses of cephalosporin (cefazolin, 500 mg intramuscularly) postoperatively, (c) treatment as in protocol group b plus 1 week of cephalosporin (cefazolin, 500 mg intramuscularly, twice daily), and (d) treatment as in protocol group b plus 2 weeks of cephalosporin (cefazolin, 500 mg intramuscularly, twice daily). All grafts were sterilely removed between 3 and 4 weeks after implantation. There were no anastomotic disruptions and all grafts were patent at the time of removal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Treatment of established prosthetic vascular graft infection with antibiotics preferentially concentrated in leukocytes

The efficacy of treating established vascular graft infections with rifampin and clindamycin (preferentially concentrated in leukocytes) and cefazolin (not concentrated in leukocytes) was studied in a canine model. Infrarenal aortic, 6 mm by 6 cm knitted Dacron double velour grafts were implanted and infected with 10(8) colony-forming units (CFU) of coagulase-positive Staphyloccus aureus organisms injected intravenously immediately after graft placement. Antibiotic therapy was instituted at 3 months postimplantation. Three groups were studied: (I) untreated controls (n = 3); (II) therapy with intravenous cefazolin 15 mg/kg/8 hr for 28 days (n = 7); and (III) combined therapy with intravenous rifampin 13 mg/kg/24 hr and intravenous clindamycin 13 mg/kg/8 hr for 28 days (n = 7). Grafts were removed for quantitative bacteriologic studies after the 28-day course of therapy. Two group I control grafts remained patent with 6.4 X 10(6) and 8.1 X 10(3) CFU S. aureus/gm of graft. The third control graft was thrombosed. Two group II animals demonstrated 1.6 X 10(7) and 2.3 X 10(5) CFU S. aureus organisms/gram of graft, respectively; the remaining five group II grafts were free of organisms. All group III grafts were sterile--a significant difference (p less than 0.05) from group I grafts. In this experimental model, established prosthetic graft infections were eradicated by intensive treatment with antibiotics preferentially concentrated in leukocytes.     

兔胫骨慢性骨髓炎动物模型的建立

目的 探讨采用胫骨近段髓腔注射不同浓度的ATCC25923金黄色葡萄球菌菌液诱导的骨髓炎模型与菌液浓度的关系.方法 36只健康新西兰大白兔随机分为4组,其中实验组A、B、C各10只,对照组6只.采用胫骨近段髓腔注射0.1 ml 5%鱼肝油酸钠和不同浓度的ATCC25923金黄色葡萄球菌菌液的方法诱导骨髓炎,其中A组注入0.1 ml菌液浓度为3×108 CFU/ml的ATCC25923金黄色葡萄球菌,B组注入0.1 ml菌液浓度为3×109 CFU/ml的ATCC25923金黄色葡萄球菌,C组注入0.3 ml菌液浓度为3×109 CFU/ml的ATCC25923金黄色葡萄球菌,对照组注入0.1 ml生理盐水.不用抗生素来预防菌血症,4周后采用大体观察,放射影像和组织病理学等方法对诱导的骨髓炎模型进行评价分级.结果 所有大白兔都可以看到早期局部组织肿胀、病腿跛行,不同程度食欲减退,同时伴有体质量增长缓慢.造模后4周后,实验组动物出现不同程度的骨密度降低,骨小梁纤细,数目减少,骨小梁间隙加宽,骨皮质变薄,骨溶解,死骨形成,新骨形成;病理切片显示实验组动物出现不同程度的中性嗜酸性粒细胞浸润,骨髓腔内髓细胞不同程度坏死,间质出血;采用兔金黄色葡萄球菌骨髓炎模型严重程度分级大体标本观察和放射学检测标准对所诱导模型进行严重程度分级:A组属1～2级(其中属1级2只,属2级7只),B组属2～3级(其中属2级3只,属3级6只),C组属3～4级(其中属3级2只,属4级5只).结论 采用胫骨近段髓腔注射细菌菌液的方法能够较好的诱导骨髓炎模型,模型的严重程度随注入的细菌量的增多而加重,兔金黄色葡萄球菌骨髓炎模型严重程度分级大体标本观察和放射学检测标准能够较好的反映骨髓炎的严重程度分级.     

Prevention of prosthetic vascular graft infection by rifampicin impregnation of a protein-sealed Dacron graft in combination with parenteral cephalosporin.

Antibiotic-impregnated prosthetic vascular grafts have been shown to be highly resistant to bacterial contamination in animal models. The aim of this study was to assess if graft infection in an animal model challenged with local bacterial contamination could be reduced further by the use of rifampicin soaking of a protein-sealed Dacron graft in addition to the prophylaxis provided by perioperative intravenous cephalosporin. Of 20 Merino sheep given cefoxitin intravenously before the induction of anaesthesia, ten had a rifampicin treated Dacron graft implanted into the common carotid artery (group 1), and ten received an untreated Dacron graft (group 2). Before wound closure the grafts were inoculated with 1 ml of 10(8) colony forming units per ml of Staphylococcus aureus. After three weeks the grafts were removed and cultured. Group 1 sheep had fewer graft infections (two of 10) compared to group 2 (six of eight survivors), this difference being statistically significant (p = 0.03; Fisher exact test). It is concluded that rifampicin treatment of protein-sealed Dacron grafts combined with intravenous cefoxitin provides more protection from contaminating Staphylococcus aureus than intravenous cefoxitin alone in this animal model.     

Prophylaxis against Staphylococcus aureus vascular graft infection with mupirocin-soaked, collagen-sealed dacron

A rat model was used to investigate the efficacy of mupirocin in the prevention of vascular prosthetic graft infections. The effect of mupirocin-soaked Dacron was compared with the effect of rifampin-soaked, collagen-sealed Dacron in the rat model of graft infection caused by methicillin-susceptible Staphylococcus aureus and methicillin-resistant S. aureus. Graft infections were established in the back subcutaneous tissue of 195 adult male Wistar rats by implantation of 1-cm(2) Dacron prostheses followed by topical inoculation with 5 x 10(7) colony-forming units of S. aureus. The study included a control group (no graft contamination), two contaminated groups that did not receive any antibiotic prophylaxis, two contaminated groups in which perioperative intraperitoneal amoxicillin clavulanate prophylaxis (50 mg/kg) was administered, four contaminated groups that received mupirocin- or rifampin-soaked graft, and four contaminated groups that received mupirocin- or rifampin-soaked graft and perioperative intraperitoneal amoxicillin clavulanate prophylaxis (50 mg/kg). The grafts were sterilely removed 7 days after implantation and the infection was evaluated by using sonication and quantitative agar culture. Data analysis showed that the efficacy of mupirocin against both strains was significantly different from that of the untreated control. In addition, mupirocin was more effective than rifampin against the methicillin-resistant strain. Finally, only the combination of mupirocin and amoxicillin clavulanate produced complete suppression of growth of all strains.     

Treatment of vascular graft infection by in situ replacement with a rifampin-bonded gelatin-sealed Dacron graft

Purpose: 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.Methods: 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° 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.Results: 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 × 10⁶ CFU/cm²), in initially implanted grafts of groups II (9 ± 1.1 × 10⁵ CFU/cm²) and III (1.3 ± 1.5 × 10⁶ CFU/cm²), and in untreated replacement grafts of group II (1.7 ± 2.5 × 10⁶ CFU/cm²). Blood culture results and culture results of liver, spleen, kidney, and lung specimens at the time of sacrifice were negative.Conclusion: 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. (J VASC SURG 1994;19:739-44.)     

Laser-induced shock waves enhance sterilization of infected vascular prosthetic grafts

BACKGROUND AND OBJECTIVE: Bacteria that cause infection of vascular prosthetic grafts produce an exopolysaccharide matrix known as biofilm. Growth in biofilms protects the bacteria from leukocytes, antibodies and antimicrobial drugs. Laser-generated shock waves (SW) can disrupt biofilms and increase drug penetration. This study investigates the possibility of increasing antibiotic delivery and sterilization of vascular prosthetic graft. STUDY DESIGN/MATERIALS AND METHODS: Strains of Staphylococcus epidermidis and S. aureus were isolated from infected prosthetic grafts obtained directly from patients. Dacron grafts were inoculated with the isolated bacteria, which were allowed to form adherent bacterial colonies. The colonized grafts underwent the following treatments: (a) antibiotic (vancomycin) alone; (b) antibiotic and SW (c) saline only; and (d) saline and SW. Six hours after treatment, the grafts were sonicated, the effluent was cultured and the colony forming units (CFU) were counted. RESULTS: CFU recovered from control grafts colonized by S. epidermidis were comparable: saline, 3.05 x 10(8) and saline+SW 3.31 x 10(8). The number of S. epidermidis CFU diminished to 7.61 x 10(6) after antibiotic treatment but the combined antibiotic+SW treatment synergistically decreased CFU number to 1.27 x 10(4) (P<0.001). S. aureus showed a higher susceptibility to the antibiotic: 2.26 x 10(6) CFU; antibiotic +SW treatment also had an incremental effect: 8.27 x 10(4) CFU (P<0.001). CONCLUSIONS: This study demonstrates that laser-generated shock waves have no effects alone, but can enhance the effectiveness of antibiotics against bacteria associated with prosthetic vascular graft biofilms, suggesting that this treatment may be of value as adjunctive therapy for prosthetic graft infections.     

Laparoscopic diagnosis and treatment of aortic vascular prosthetic graft infections in a porcine model.

OBJECTIVES: To study the feasibility and efficacy of experimental laparoscopy in the diagnosis of aortic graft infection in pigs. MATERIAL AND METHODS: Eight pigs had an aortic tube graft implanted and inoculated with either 5 x 10(4) or 10(6) CFU of Staphylococcus aureus ATCC 29213. Laparoscopy was performed after a median of 20 days with debridement and sampling for bacterial culture. Thereafter, the grafts were locally soaked in rifampicin and postoperatively, the pigs received rifampicin and ciprofloxacin orally for two weeks and were then sacrificed. RESULTS: All pigs developed graft infection. One pig died from severe clostridial septicaemia before laparoscopy could be performed. The remaining pigs had all samples for bacterial culture taken by laparoscopy from the inflamed tissue. The temperature dropped significantly after laparoscopy, and no macroscopic signs of infection presented at autopsy. However, only culture from one pig was without S. aureus at autopsy. CONCLUSIONS: Laparoscopy is a potential diagnostic tool for aortic graft infection and also affords the opportunity to carry out bacteriological sampling and local antibiotic treatment. The efficacy of laparoscopic treatment needs further evaluation.