Parenteral Antibiotics and Selective Intestinal Decontamination Do Not Prevent Enteric Bacterial Overgrowth or Translocation Observed in a Swine Model of Small Bowel Transplantation

Abstract

Alterations in the luminal microflora and increased intestinal translocation have been reported to occur following experimental and clinical small bowel transplantation (SBT). Selective intestinal decontamination (SID) has been used to prevent luminal overgrowth and bacterial translocation. Despite the wide use of SID in clinical SBT, there are no data supporting its usefulness in this situation. Thus, the aim of this investigation was to examine the effects of cyclosporine A (CsA) and SID upon bacterial overgrowth and translocation in a swine model of SBT. Nineteen Large White female pigs weighing 30 ± 2 kg underwent a total orthotopic SBT and were randomly allocated to one of the following experimental groups as follows: Group 1 (No. 8) CSA 25 mg/kg body weight (b.w.)/day administered subcutaneously and Cefazolin 2 g/day im. Group 2 (No. 6) received the identical immunosuppression but the Cefazolin 2 g/day im was discontinued on the 5th Postoperative Day (pod) and switched to a SID regimen consisting of Vancomycin, 1 g, Nystatin, 500,000 IU, Colistin, 1,500,000 IU, and Tobramycin, 100 mg, given through a gastrostomy tube. Group 3 (No. 5) received no immunosuppression but antibiotic consisting of Cefazolin 2 g im/day. Group 4 (No. 7) underwent a small bowel autotransplantation. Group 4 received SID as in group 2 but no immunosuppression was given. Finally, 17 normal animals were sham-operated and were used as normal controls (N group). The animals in groups 1, 2, and 4 were sacrificed on the 29th pod. Those in group 3 were sacrificed on the 7th pod. Samples from graft, native bowel, liver, kidney, skin, and lungs were processed for histologic evaluation. Moreover, samples from the graft (proximal, middle, and distal) and adjacent mesenteric lymph nodes were harvested aseptically and cultured for both aerobes as well as for anaerobes. Significant increases in the number of aerobes and anaerobes were found in the proximal graft of all groups studied compared to the normal controls. The rate of intestinal translocation was 19% in the normal controls and increased to 88, 83, 100, and 100% in groups 1, 2, 3, and 4, respectively. Based upon these data, it can be concluded that SID is no better than a parenteral antibiotic regimen at preventing bacterial overgrowth following SBT. Moreover, neither therapy reduces the high rate of bacterial translocation to mesenteric nodes seen in arrivals following experimental SBT.