Use of an experimental model to evaluate infection resistance of meshes in abdominal wall surgery.

BACKGROUND: Staphylococcal species are the most common organisms causing prosthetic mesh infections, however, infections due to rapidly growing mycobacteria are increasing. This study evaluates the resistance of biomaterial for abdominal wall prostheses against the development of postoperative infection in a rat model. MATERIAL AND METHODS: In 75 rats, we intramuscularly implanted three different types of prostheses: (1) low-density polypropylene monofilament mesh (PMM), (2) high-density PMM, and (3) a composite prosthesis composed of low-density PMM and a nonporous hydrophilic film. Meshes were inoculated with a suspension containing 108 colony-forming units of Staphylococcus aureus, Staphylococcus epidermidis, Mycobacterium fortuitum, or Mycobacterium abscessus before wound closure. Animals were sacrificed on the eighth day postoperatively for clinical evaluation, and the implants were removed for bacteriologic analyses. RESULTS: Prostheses infected with S aureus showed a higher bacterial viability, worse integration, and clinical outcome compared with infection by other bacteria. Composite prostheses showed a higher number of viable colonies of both M fortuitum and Staphylococcus spp., with poorer integration in host tissue. However, when the composite prosthesis was infected with M abscessus, a lower number of viable bacteria were isolated and a better integration was observed compared with infection by other bacteria. CONCLUSIONS: Considering M abscessus, a smaller collagen-free contact surface shows better resistance to infection, however, depending on the type of bacteria, prostheses with a large surface, and covered with collagen shows reduced resistance to infection, worse integration, and worse clinical outcome.

Histopathological changes associated to an absorbable fibrin patch (Tachosil®) covering in an experimental model of high-risk colonic anastomoses.

BACKGROUND: TachoSil® is a fibrin sponge that contains fibrinogen and thrombin and is a useful adjuvant to enhance control of air leaks in thoracic surgery and to control bleeding in vascular and general surgery. Its use in intestinal surgery to prevent suture dehiscence is currently under investigation. MATERIAL AND METHODS: We report the results of a prospective randomized experimental study on 33 large white pigs in which a high-risk suture was created by induction of ischemia. We randomly employed TachoSil® to cover the anastomosis in half of the animals compared to a control group of uncovered anastomosis. After euthanasia, postmortem analysis was performed describing the findings related to anastomotic leakage, peritonitis and grade of adhesions. The entire anastomosis was resected in bloc and sent for histopathological analysis. A single blinded-pathologist evaluated the histopathological features of the specimens. RESULTS: We found statistically significant differences favouring the patch in decreasing leakage in the covered group. The healing process did not show significant differences between groups, although a higher rate of microscopic abscess was observed in the covered group. CONCLUSION: The use of fibrin sealants covering high-risk intestinal sutures has a positive effect in avoiding macroscopic anastomotic leakage. The patch did not have any influence in the anastomotic healing process, however, as a result of the effect in containing the inflammatory response, it may increase the rate of abscess.