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Acute rejection after small bowel transplantation (SBTx) may facilitate bacterial translocation (BT) and subsequent changes in the liver, spleen, and lungs. This study investigated whether BT occurs after acute rejection and whether this is followed by changes in the structure of the intestine and the phagocytic organs interposed between the gut and the general circulation. Orthotopic SBTx was performed in allogeneic (ALLO) rat-strain combinations (BN-Wistar, n=5). For comparison we used syngeneic SBTx (SYN) (BN-BN, n=6) controls. Animals were sacrificed on postoperative day 7. Mesenteric lymph nodes and portal and caval blood were cultured for aerobes and anaerobes. Escherichia coli beta-galactosidase DNA was assessed by polymerase chain reaction in the blood samples. Intestine, liver, spleen, and lung protein and DNA contents were measured. Histologic changes were graded according to standard criteria of acute rejection. For comparisons we used chi(2) and nonparametric Mann-Whitney test with a threshold of significance of p<0.05. ALLO rats lost more weight after SBTx than SYN rats (-13.02+/-4.39% vs. -8.04+/-5.08% of preoperative weight), although the difference was not significant (ns). A variable degree of graft rejection was histologically demonstrated in all ALLO rats, and DNA/protein content in the graft was significantly higher in this group (0.245+/-0.85 vs. 0.134+/-0.21, p<0.05). Gram-negative enteric bacteria were found in 4/5 ALLO and 4/6 SYN rats (ns), and aerobic Gram-positive bacteria in 2/5 and 3/6 (ns), respectively. Anaerobic growth occurred in mesenteric lymph nodes in one ALLO rat and in the bloodstream in another one. E. coli DNA was isolated in none of the ALLO but in two SYN rats (ns). BT was frequent after SBTx in both syngeneic and allogeneic strain combinations. Contrary to our expectations, BT after SBTx was not higher in ALLO group rats. However, anaerobic germs were isolated only in this group.

Abstract: Rejection after small bowel transplantation (SBTx) may allow bacterial translocation damaging the liver and lungs. This study investigated these issues in a rat model of chronic rejection. Materials and Methods: Orthotopic SBTx was performed in syngeneic (SYN) (ACI-ACI, n = 8) and allogeneic (ALLO) (ACI-Lewis, n = 8) rat strain combinations. Cyclosporine was given to ALLO rats for 28 days. Animals were sacrified between 55 and 65 days. Lymph nodes and venous samples were cultured; Escherichia coli DNA was assessed by polymerase chain reaction. We measured intestine, liver, spleen, and lung protein and DNA contents. Chronic rejection was histologically confirmed. Results: Two of eight and four of eight rats died in the first week after SYN and ALLO SBTx, respectively. There were no differences in organ weights or DNA and protein contents compared with the controls. Gram-negative enteric bacteria were found in two of four ALLO and two of six SYN rats (ns), and aerobic gram-positive were found in two of four and two of six (ns), respectively. Anaerobic growth occurred in mesenteric lymph nodes in only one ALLO rat. E. coli DNA was negative in all animals. Lungs were severely emphysematous in ALLO rats with no histologic changes observed in the other phagocytic organs. Mild rejection was found in the intestine of ALLO rats. Conclusions: Bowel lesions in ALLO rats might be consistent with chronic rejection and lung lesions could be related to bacterial translocation after SBTx. However, contrary to our expectations, no significant bacterial translocation was demonstrated in either group at the end of the experiments. [Copyright &y& Elsevier]