Role of lymphatics in bacterial translocation from intestine in burn rats

OBJECTIVE: To investigate the role of lymphatics in bacterial translocation from intestine of rats with burn. METHODS: Escherichia coli (E. coli) labeled with chloromethylbenzamidodialkylcarbocyanine (CM-DIL) were prepared. Sixty adult male Wistar rats were randomly divided into scald group and sham injury group according to the envelope method, with 30 rats in each group. Rats in both groups were gavaged with 0.5 mL fluid containing CM-DIL-labeled E. coli. Rats in scald group were inflicted with 30% TBSA deep partial-thickness scald (verified by pathological section) and resuscitated with fluid. Rats in sham injury group were sham injured by bathing in 25 degrees C water for 10 s (verified by pathological section) and also received with fluid infusion. Mesenteric lymph node (MLN), liver, mesenteric lymph fluid (MLF), and liver vein blood (LVB) were harvested at post injury hour (PIH) 2, 24, and 72. Bacteria translocation was detected with fluorescent tracing technique and bacteria culture. The endotoxin content in above-mentioned four kinds of specimens was quantitatively determined with chromogenic substrate limulus amebocyte lysate. The carrying capacity of endotoxin in MLF and LVB was calculated. Data were processed with t test or one-way analysis of variance. RESULTS: (1) Living bacteria were in short-stick form, and they were seen moving in single or in doubles or triples in sample fluid. Dead bacteria were in irregular aggregates. Labeled bacteria in small amount were detected in sham injury group, their number peaked at PIH 24. A large amount of labeled bacteria were detected in scald group at PIH 2, which peaked at PIH 24 and decreased at PIH 72. The largest amount of labeled bacteria were found in MLN in scald group as compared to those in the other samples, and the number peaked at PIH 24 [(5872 +/- 1976) x 10(3) CFU/g], which was obviously higher than that [(216 +/- 110) x 10(3) CFU/g, t = 30.129, P = 0.000] in sham injury group. The number of bacteria decreased at PIH 72, but it was still significantly different from that in sham injury group ( t = 4.323, P = 0.000). The number of bacteria in LVB was the smallest. (2) 29 (24.2%) samples out of the 120 samples in sham injury group were positive for bacteria. 72 (60.0%) samples out of the 120 samples in scald group were positive for bacteria. No alive bacterium was detected at any time point in LVB sample in both group; the other three samples were detected with alive bacteria since PIH 2. There were more alive bacteria detected in MLN and liver as compared with the other two kinds of samples in scald group. The amount of bacteria in MLN, liver, and MLF in scald group were higher than those in sham injury group (with t value respectively 4.353, 4.354, 4.965, P values all equal to 0.000). (3) The endotoxin level in each kind of sample at each time point was obviously higher in scald group than that in sham injury group, and it peaked at PIH 2 in liver and MLF. The difference of endotoxin level among 4 kinds of samples in scald group at PIH 2 was statistically significant ( F = 258.47, P = 0.000), and the endotoxin level was higher in liver, MLN, and MLF. They were obviously higher than those in sham injury group (with t value respectively 43.378, 43.123, 22.423, P values all equal to 0.000). The endotoxin level in MLF was 9 times of that in LVB. (4) The carrying capacity of endotoxin in LVB and MLF at each time point in scald group was higher than that in sham injury group. CONCLUSIONS: CM-DIL marked bacteria can reflect the microbial translocation condition. The lymphatic route is an important pathway for bacteria translocation.