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.     

Seromuscular enteric pedicles and prosthetic aortic graft complications in a porcine abdominal trauma model. An experimental study

BACKGROUND/AIMS: Abdominal vascular trauma may require prosthetic grafting despite peritoneal contamination by concurrent visceral injury. This study tested the use of vascularized, seromuscular enteric pedicles (VSEP) against the development of vascular prosthetic complications, in a porcine abdominal trauma model. METHODS: Eight pigs underwent aortic transection and reconstruction with a Dacron interposition graft (DIG). A standard bacterial inoculum soaked the DIG in situ. An enteric segment was isolated on its mesenteric pedicle, and the mucosa stripped. This VSEP was wrapped around the DIG and oversewn. Animals received antibiotics for 5 days. Endpoints were 2-week survival, or evidence of sepsis. The animals underwent explantation of the DIG, VSEP, and native aorta for the purposes of histological, and microbiological analyses, and scanning electron microscopy (SEM). Outcome measures were graft infection, graft thrombosis, tissue incorporation, and anastomotic integrity. RESULTS: Two pigs were excluded for perioperative death. All study group animals (n = 6), survived 2 weeks. Infection and thrombosis were found in 0/6 (0%). Incorporation and anastomotic integrity were evident in 6/6 (100%). VSEP had intact blood supplies. SEM demonstrated viable muscle, microcirculation, and fibroplasia in VSEP. CONCLUSION: We conclude that VSEP may help prevent prosthetic graft complications in the contaminated setting.     

Temporin A as a prophylactic agent against methicillin sodium-susceptible and methicillin sodium-resistant Staphylococcus epidermidis vascular graft infection

OBJECTIVE: The purpose of this study was to investigate the efficacy of temporin A as a prophylactic agent in a rat model of vascular graft infection from methicillin sodium-susceptible and methicillin sodium-resistant Staphylococcus epidermidis. METHODS: The prospective, randomized, controlled animal study set in a research laboratory in a university hospital used 280 adult male Wistar rats (weight range, 280 to 350 g). Graft infections were established in the back subcutaneous tissue of rats with implantation of 1-cm(2) sterile Dacron grafts followed by topical inoculation with 2 x 10(7) colony-forming units of S epidermidis. The study for each staphylococcal strain included: one control group (no graft contamination), one contaminated group that did not receive any antibiotic prophylaxis, one contaminated group that received temporin A-soaked graft, two contaminated groups that received perioperative intraperitoneal cefazolin (30 mg/kg) or vancomycin hydrochloride prophylaxis (10 mg/kg), and two contaminated groups that received temporin A-soaked graft and perioperative intraperitoneal cefazolin (30 mg/kg) or vancomycin hydrochloride (10 mg/kg) prophylaxis. All grafts were explanted at 7 days after implantation. The main outcome measure was quantification of bacterial contamination. RESULTS: Overall, the perioperative prophylaxis based on soaked grafts was not significantly different to that of parenteral vancomycin hydrochloride. Only the combination between temporin A and vancomycin hydrochloride produced a complete bacterial inhibition for both strains. CONCLUSION: Temporin A showed a similar antibacterial in vitro activity against the two different strains. The in vivo results suggest its potential use in providing prophylaxis to direct graft contamination when used in combination with parenteral vancomycin hydrochloride.     

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.     

Efficacy of Rifampin-Levofloxacin as a Prophylactic Agent in Preventing Staphylococcus epidermidis Graft Infection

OBJECTIVES: To investigate the efficacy of levofloxacin in the prevention of vascular prosthetic graft infection in a rat model. METHODS: Graft infections were established in the subcutaneous tissue of 225 male Wistar rats by implantation of Dacron prostheses followed by topical inoculation with methicillin-susceptible and methicillin-resistant S. epidermidis. The study included a group without contamination, two contaminated groups without prophylaxis, two contaminated groups with intraperitoneal levofloxacin prophylaxis, two contaminated groups with intraperitoneal cefazolin prophylaxis, two contaminated groups with intraperitoneal teicoplanin prophylaxis and six contaminated groups with rifampin-soaked graft and intraperitoneal levofloxacin, cefazolin or teicoplanin prophylaxis. The grafts were removed after 7 days and evaluated by quantitative culture. RESULTS: The efficacy of levofloxacin against the methicillin-susceptible strain was not different to that of cefazolin or teicoplanin. Levofloxacin showed slight less efficacy than teicoplanin against the methicillin-resistant strain. The combination levofloxacin-rifampin demonstrated to be similarly effective to the combination rifampin-teicoplanin and more effective than the combination rifampin-cefazolin against both strains. CONCLUSIONS: Rifampin-levofloxacin combination seems useful for the prevention of late-appearing vascular graft infections caused by S. epidermidis.     

Evaluation of three techniques for documenting Staphylococcus epidermidis vascular prosthetic graft infections

Staphylococcus epidermidis (S. epidermidis) vascular prosthetic graft infections are notoriously hard to detect. Three different techniques of determining whether vascular prosthetic grafts were infected using a dog model were evaluated. Aortic angiograms were compared with nuclear magnetic resonance (NMR) imaging and systemic norepinephrine (NE) kinetics to determine if either newer technique would be more reliable than standard angiograms. Twelve dogs were randomized to control (n = 6) or infected groups (n = 6). All dogs had a 5 cm section of their infrarenal aorta replaced with knitted Dacron vascular prosthetic graft. The grafts in the infected group were contaminated by soaking them in a broth containing S. epidermidis. NE production and clearance rates were calculated for all animals after an infusion of 3H-NE using the steady-state radionuclide tracer methodology. One week following graft insertion, dogs were reanesthetized, and the 3H-NE infusion and measurements were repeated. Standard angiograms and NMR imaging were also performed. Once all tests were performed, the prosthetic grafts were removed for cultures. Comparisons between the initial and final norepinephrine measurements for each group were made using the nonparametric Wilcoxon two-sample test, while comparisons between the groups were made by chi square or the Student's t test. Angiogram results were similar for control and infected animals. Angiograms missed disruption of the proximal anastomosis found in three of the six infected dogs at graft removal. None of the six control animals, while five of the six infected animals, had localized areas of high signal intensity on NMR imaging (P less than 0.01) suggesting abscess formation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Surface biofilm disruption. Enhanced recovery of microorganisms from vascular prostheses

Ultrasonic oscillation (sonication) of explanted vascular prosthetic graft material can disrupt surface biofilms and increase the recovery of adherent microorganisms. Recovery of microorganisms from vascular grafts was studied in a canine model of Staphylococcus epidermidis graft contamination (N = 26) and on graft material excised from patients undergoing femoral anastomotic pseudoaneurysm repair (N = 7). Surface biofilm disruption by sonication significantly increased the incidence of positive cultures of excised graft material compared with broth (P less than .010) and blood agar plate (P less than .005) culture techniques. The S epidermidis was recovered from 31% of the canine vascular grafts and 100% of the clinical specimens. The in vitro production of a glycocalyx "slime" was demonstrated in 73% of the recovered staphylococcal strains. The formation of an adherent bacteria biofilm on implanted vascular prostheses is not an uncommon occurrence and is an important factor in the pathogenesis of anastomotic pseudoaneurysm formation and late graft infection.     

Identification of Staphylococcus epidermidis vascular graft infections: a comparison of culture techniques

Culture of prosthetic material is routinely used to exclude or implicate infection in the pathogenesis of late-appearing graft complications. In a canine model of aortic graft infection caused by a bacterial biofilm, the influence of culture media (blood agar and tryptic soy broth) and mechanical surface biofilm disruption (tissue grinding and ultrasonic oscillation) on microorganism recovery was determined. Dacron prostheses colonized in vitro with Staphylococcus epidermidis were implanted in the infrarenal aortas of 36 dogs. After 3 weeks an infection with anatomic characteristics of late graft infection in humans was present. Explantation (+/- surface biofilm disruption) of infected grafts showed broth culture was superior (p less than 0.001) to agar media in confirming infection. The recovery rate of S. epidermidis was 30% with agar media, was 72% with broth media alone, and was 83% with broth media plus biofilm disruption. In situ replacement of infected grafts plus parenteral antibiotics resulted in early (1 month) healing of 31 grafts without signs of infection. All replacement grafts were sterile when cultured in broth media alone, but the addition of biofilm disruption isolated the study strain from eight (22%) of 36 grafts (p less than 0.01). Biofilm disruption by tissue grinding or sonication increased bacteria recovery equally. When biofilm bacterial concentration was less than 100 colony-forming units/cm2 of graft, only culture in broth media reliably recovered microorganisms. In the absence of perigraft inflammation, microbiologic recovery techniques that identify bacterial biofilms are necessary to exclude infection in studies concerning the pathogenesis of late graft complications or the treatment of S. epidermidis prosthetic infections.     

Quinupristin/dalfopristin bonding in combination with intraperitoneal antibiotics prevent infection of knitted polyester graft material in a subcutaneous rat pouch model infected with resistant Staphylococcus epidermidis.

OBJECTIVE: to investigate the efficacy of quinupristin/dalfopristin in the prevention of prosthetic graft infection in a rat subcutaneous pouch model. METHODS: graft infections were established in the subcutaneous tissue of 140 male Wistar rats by implantation of Dacron prostheses followed by topical inoculation with Staphylococcus epidermidis with intermediate resistance to glycopeptides. The study included one group without contamination, one contaminated group without prophylaxis, one contaminated group that received 50mg/l quinupristin/dalfopristin-soaked graft, one contaminated group that received 10mg/kg intraperitoneal levofloxacin, one contaminated group that received 3mg/kg intraperitoneal doxycycline, and two contaminated groups that received 50mg/l quinupristin/dalfopristin-soaked plus 10mg/kg intraperitoneal levofloxacin or 3mg/kg intraperitoneal doxycycline. Each group included 20 animals. The grafts were removed after 7 days and evaluated by quantitative culture. RESULTS: quinupristin/dalfopristin showed a significantly higher efficacy than levofloxacin and doxycycline, even though quantitative graft cultures for rats that received only quinupristin/dalfopristin-soaked graft showed bacterial growth. Otherwise, the efficacy of levofloxacin was similar to that of doxycycline. Only the group treated with quinupristin/dalfopristin combined with levofloxacin or doxycycline showed no evidence of staphylococcal infection. CONCLUSIONS: quinupristin/dalfopristin as adjunctive topical antibiotic prophylaxis can be useful for the prevention of vascular graft infections caused by staphylococcal strains with high levels of resistance.     

Anastomotic tensile strength following in situ replacement of an infected abdominal aortic graft

The tensile strength and histologic features of anastomotic bonding were studied prior to and following in situ replacement of aortic vascular prostheses infected by Staphylococcus epidermidis. Sterile (n = 6) and infected (n = 19) Dacron grafts were used to replace the abdominal aorta of 25 dogs. After five weeks, grafts were explanted, and peak tensile force (measured in kilograms) required for anastomotic disruption was measured using a linear gain tensiometer. Anastomotic tensile strength (mean +/- SEM) of infected grafts (5.4 +/- 0.5 kg) was decreased when compared with that of sterile, control grafts (9.0 +/- 0.9 kg). The decreased anastomotic tensile strength of infected grafts was the result of an inflammatory aortitis adjacent to the suture line. Only grafts infected with the study strain of bacteria demonstrated signs of infection. In 19 dogs, the graft infection was treated by graft excision, antibiotic administration, and in situ graft replacement (Dacron or polytetrafluoroethylene prostheses). After five weeks and 12 weeks, anastomotic tensile strength of polytetrafluoroethylene (10.6 +/- 0.6 kg) and Dacron (10.8 +/- 0.5 kg) replacement grafts was similar to that of uninfected control grafts. In situ replacement of vascular prostheses infected by S epidermidis can result in graft healing with normal anastomotic bonding.     

Use of rifampin-soaked gelatin-sealed polyester grafts for in situ treatment of primary aortic and vascular prosthetic infections

BACKGROUND: In situ treatment of artery/graft infection has distinct advantages compared to vessel excision and extra-anatomic bypass procedures. Based on animal studies of a rifampin-soaked, gelatin-impregnated polyester graft that demonstrated prolonged in vivo antibacterial activity, this antibiotic-bonded graft was used selectively in patients for in situ treatment of low-grade Gram-positive prosthetic graft infections or primary aortic infections not amenable to excision and ex situ bypass. METHODS: In a 5-year period (1995-1999), 27 patients with prosthetic graft infection (aortofemoral, n = 18, femorofemoral, n = 3; axillofemoral, n = 1) or primary aortic infection (mycotic aneurysm, n = 3; infected AAA, n = 2) underwent excision of the infected vessel and in situ replacement with a rifampin soaked (45-60 mg/ml for 15 min) gelatin-impregnated polyester graft. All prosthetic graft infections were low grade in nature, caused Gram-positive bacteria (Staphylococcus epidermidis, 16; Staphylococcus aureus, 5; Streptococcus, 1), and were treated electively. Patients with mycotic aortic aneurysm presented with sepsis and underwent urgent or emergent surgery. RESULTS: Two (8%) patients died-1 as a result of a ruptured Salmonella mycotic aortic aneurysm and the other from methicillin-resistant S. aureus infection following deep vein replacement of an in situ replaced femorofemoral graft. No amputations or late deaths as the result of vascular infection occurred in the 25 surviving patients. Two patients developed recurrent infection caused by a rifampin-resistant S. epidermidis in a replaced aortofemoral graft limb and were successfully treated with graft excision and in situ autogenous vein replacement. Eighteen patients remain alive and clinically free of infection after a mean follow-up interval of 17 months. CONCLUSIONS: In situ replacement treatment using a rifampin-bonded prosthetic graft for low-grade staphylococcal arterial infection was safe, durable, and associated with eradication of clinical signs of infection. Failure of this therapy was the result of virulent and antibiotic-resistant bacterial strains.     

Infection of vascular prostheses caused by bacterial biofilms

A canine model was developed to study the efficacy of graft replacement as treatment for vascular prosthesis infections from Staphylococcus epidermidis. Infrarenal aortic graft infections were established in 18 dogs by implantation of Dacron prostheses colonized in vitro with a slime-producing strain of S. epidermidis to form an adherent bacteria-laden biofilm (5 X 10(6) colony-forming units/cm2 graft). Study animals developed a graft infection with anatomic and microbiologic characteristics typical of late prosthetic graft infections in humans (sterile perigraft exudate, absent graft incorporation, and normal serum leukocyte count and sedimentation rate). The S. epidermidis study strain was isolated from 14 of 18 explanted grafts (78%) by mechanical disruption of the graft surface biofilm and culture in broth media. Four dogs with sterile graft cultures had histologic evidence of bacterial infection. The established prosthetic surface biofilm infection was treated by graft excision, parenteral cefazolin, and graft replacement with a Dacron or polytetrafluoroethylene (PTFE) vascular prosthesis. One month after graft replacement, no PTFE graft had signs of infection, but perigraft exudate and inflammation involved three of nine Dacron grafts (33%). The study strain was recovered from four of nine PTFE grafts (44%) and two of nine Dacron (22%) replacement grafts (p greater than 0.05). Prosthetic replacement of Dacron prostheses infected by S. epidermidis as a bacteria-laden surface biofilm can result in early graft healing, but persistent colonization of one third of replacement grafts signify that recurrent clinical infection remains a risk.     

Differential effects of a gram-negative and a gram-positive infection on autogenous and prosthetic grafts

A canine model was developed to study the differential response of a gram-negative and a gram-positive bacterial infection on autogenous and prosthetic grafts. After replacing segments of the femoral arteries of 15 dogs with autogenous vein in one groin and polytetrafluoroethylene in the contralateral groin, 10(8) colony-forming units of nonmucin-producing Staphylococcus epidermidis (five dogs), Pseudomonas aeruginosa (five dogs), or sterile saline solution (five dogs) were directly inoculated onto the grafts. The grafts were examined 7 to 10 days after implantation. None of the control dogs exhibited inflammatory signs, and no grafts or anastomoses disrupted. S. epidermidis was unrecoverable from either graft material in any of the animals, although histologic evaluation confirmed neutrophils and bacteria in four of five animals in the vein and polytetrafluoroethylene groups. No dog inoculated with S. epidermidis had graft or anastomotic disruption. By contrast, P. aeruginosa was recovered from both types of grafts in all inoculated animals. Neutrophils, bacteria, and microabscesses were observed in all of these animals. In addition, three of five polytetrafluoroethylene grafts and all five vein grafts disrupted either at the anastomoses or in the body of the vein graft. Therefore S. epidermidis is a less virulent organism that may persist in graft walls despite negative cultures, whereas P. aeruginosa is a highly virulent organism that can disrupt native artery, vein grafts, and anastomoses. The graft material appears to be less important than the bacteria in determining the outcome of infection.     

A "clean" technique for managing bleeding duodenal ulcer with a new aortic prosthesis: endoscopic-assisted repair of bleeding duodenal ulcer

Aortic graft infection is one of the most dreaded surgical complications. In the perioperative patient with fresh aortic prosthesis, this is a particularly complex problem. Opening the bowel changes an operation to a "clean-contaminated" or "contaminated" case. This increases the risk of all infectious complications in the patient. Theoretically, our method of repair reduces the risk of infection by eliminating the duodenotomy. The direct visualization with the endoscope replaces the need to open the potentially contaminated bowel and reduces the risk of bacterial translocation and bacteremia. By not opening the bowel, this keeps the case "clean," and likely reduces the risk of contamination and subsequent infection of the prosthetic graft. As the potential morbidity of aortic graft infection is so devastating, and now that we have the available technology and operative skill, we propose our technique as a potential alternative to possibly reduce the incidence of aortic graft infection.     

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.     

Experience with pyoktanin lavage for mediastinitis and prosthetic graft infection following thoracic aortic surgery

Pyoktanin, a triphenylmethane dye, is known to have a potent bactericidal activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA). We used pyoktanin for irrigating wounds in 2 cases of mediastinitis and prosthetic graft infection following thoracic aortic surgery. Case 1 is mediastinitis and prosthetic graft infection due to Staphylococcus epidermidis following Cabrol procedure. After irrigating the anterior mediastinum with 0.1% pyoktanin solution twice a day for 8 days, omental transposition was performed, which let to cure of the infection. Case 2 is mediastinitis due to methicillin-resistant Staphylococcus epidermidis following ascending aortic and aortic arch replacement for acute type A aortic dissection. After irrigating the wound with 0.1% pyoktanin solution twice a day for 14 days, the wound was closed primarily, which resulted in cure of the infection of the wound. Using pyoktanin at low concentrations for irrigating wound for a short period of time is considered permissible and effective for mediastinitis and prosthetic graft infection due to Gram-positive bacteria including MRSA.     

Rifampin protection against experimental graft sepsis

The risk of infection in vascular prosthetic conduits appears to be greatest in the perioperative period and the organism most frequently found is Staphylococcus aureus. Previous work suggests that antibiotics must be chemically bonded to the material to resist rapid washout caused by the flow of blood through the graft. The exception to this is rifampin, which remains fixed in Dacron prostheses after passive addition of the agent to aliquots of blood used to clot the interstices of porous Dacron grafts. This characteristic of rifampin is presumed to be caused by its poor water solubility. This potential infection resistance was challenged in a standard model of a canine infrarenal aortic graft by intravenous infusion of S. aureus organisms (10(7)) in the perioperative period. The grafts of five animals were preclotted with 9 ml of autogenous blood plus 1 ml of rifampin (60 mg/ml). A second group had similar procedures with 1 ml of cefazolin (238 mg/ml) substituted for the rifampin, and a control group had 1 ml of saline solution added to the 9 ml aliquot of blood. The animals were killed at 3 weeks and examined for clinically apparent infection. Rings of the graft material were also removed aseptically and cultured. All five grafts preclotted with cefazolin had clinical and culture evidence of infection (S. aureus), as did the grafts of three of the five control dogs. None of the grafts preclotted with rifampin was infected (p less than 0.05). Addition of rifampin to the blood used to clot the graft interstices appears to be a simple way of imparting graft resistance to perioperative sepsis.     

Experimental treatment of vascular graft infection due to Staphylococcus epidermidis by in situ replacement with a rifampin-bonded polyester graft

In situ prosthetic graft replacement (ISPGR) of an infected prosthesis raises the risk of recurrent infection in the new graft, especially in cases involving drug-resistant microorganisms. The purpose of this animal study was to evaluate in situ replacement of a vascular graft infected by a highly rifampin-resistant strain of Staphylococcus epidermidis with the use of a rifampin-bonded polyester graft. Antibiotic bonding was obtained by soaking grafts in a high dose of rifampin solution (60 mg/mL). The infrarenal abdominal aorta of 20 dogs was replaced using a polyester prosthesis infected with a highly rifampin-resistant strain of Staphylococcus epidermidis. One week later, the 18 surviving animals were randomized into three groups. Group I (n = 6) did not undergo reoperation. Group II (n = 6) underwent ISPGR using a rifampin-bonded prosthesis. Group III (n = 6) underwent ISPGR using an untreated prosthesis. All surviving animals were killed 28 days after the first procedure. Infectious signs were noted and bacteriological study was carried out on explanted prostheses and various tissue samples. The findings of this experimental study show that soaking a polyester prosthesis in a high-dose rifampin solution can prevent reinfection after in situ replacement of a prosthesis infected by a highly rifampin-resistant Staphylococcus epidermidis.     

Systemic and local antibiotic prophylaxis in the prevention of prosthetic vascular graft infection: an experimental study.

AIM: to determine if local, in addition to systemic antibiotic prophylaxis (compared to that provided by systemic prophylaxis alone) provides additional benefit in terms of reducing graft infection. METHODS: gelatin-sealed Dacron grafts were interposed in the infrarenal aorta of 36 mongrels and inoculated with 1 ml of a S. aureus suspension. Group 1 (control group) received no prophylaxis and were inoculated with 1 ml containing 10(9)cfu/ml. Group 2 (n=6) received systemic prophylaxis (1 g cephamandole) and were inoculated with 10(5) cfu/ml (n=3) or 10(7) cfu/ml (n=3). Group 3 received systemic prophylaxis (1 g cephamandole) and were inoculated with 109 cfu/ml. Group 4 received systemic prophylaxis (2 g cephamandole) and were inoculated with 10(9)cfu/ml. In group 5 and 6 grafts were soaked in a rifampicin solution before use and inoculated with 10(9) cfu/ml. Group 5 received no systemic prophylaxis and group 6 received systemic prophylaxis (1 g cephamandole). Grafts were harvested at 2 weeks, and peritonitis, perigraft abscess, anastomotic disruption and graft occlusion recorded. Swabs were taken of the graft, the perigraft tissues and the peritoneal fluid. Graft segments were incubated in broth medium. RESULTS: inoculation with 10(9) cfu/ml ensured graft infection. Systemic or local prophylaxis alone failed to prevent graft infection. Only systemic and local antibiotic prophylaxis provided significant better results than no prophylaxis at all (p<0.01) and local prophylaxis alone (p<0.05). However, total "graft sterility" was not achieved as bacteriologic analysis of the graft segments showed low bacterial counts (<10 bacteria/graft) in 5 of 6 grafts. CONCLUSION: local and systemic prophylaxis provided more protection as demonstrated by the significant decrease in the incidence of "overt" graft infection. Total "graft sterility" cannot be expected in the case of an overwhelming bacterial challenge.     

Efficacy of muscle flaps in the treatment of prosthetic vascular graft infections

Prosthetic vascular graft infection requires graft removal and often leads to limb loss. To determine whether vascularized muscle flaps could alter the course of graft infection, 18 mongrel dogs (18-29 kg) were randomized to one of three groups and underwent unilateral carotid artery bypass with 6-mm X 4-cm PTFE grafts. At implantation, the grafts were inoculated with Staphylococcus aureus, 2 x 10(7) organisms/wound. On Day 3, dogs with patent grafts underwent wound debridement, irrigation, and closure, and the treatment to which they had been randomized was carried out. Group A (n = 4, controls) received only dicloxacillin, 500 mg po bid, beginning on Day 4. Group B (n = 5) underwent transfer of a vascularized sternocephalicus muscle flap around the infected graft, but received no antibiotics. Group C (n = 5) underwent muscle transfer as in Group B and were given dicloxacillin as in Group A. Dogs were followed until anastomotic disruption occurred or for 60 days. Quantitative bacterial cultures were taken from sternocephalicus muscle and wound fluid at the time of debridement and at sacrifice. All dogs that received antibiotics without flaps or flaps without antibiotics (Groups A and B) experienced anastomotic disruption. Dogs that received both antibiotics and flaps (Group C) had a significantly lower incidence of hemorrhage (20%, P less than 0.05). At sacrifice, fewer bacterial colonies were cultured from muscle flaps of Group C as opposed to Group A dogs (0.05 +/- 0.02 x 10(5) vs 0.79 +/- 0.31 x 10(5), P less than 0.05). Muscle flaps with antibiotic therapy may prove to be effective treatment for infected prosthetic vascular grafts.