Which is the worst factor in the sepsis aggravation: translocated bacterial amount or the gut-associated lymphoid tissue activation?

Background

The intestinal hypothesis of sepsis has been attributed to bacterial translocation (BT) and the aggravation of sepsis is related to the increased vascular permeability state that potentates the BT index. In the present study we examined the BT index during sepsis with or without mesenteric lymph exclusion.

Methods

Wistar rats (± 200 g) were submitted to the BT process (Escherichia coli R6, 10 ml of 10¹⁰ colony-forming units (CFU)/ml) and nonlethal sepsis (Escherichia cloacae 89, 2 ml of 10⁷ CFU/ml) plus BT, with or without mesenteric lymph interruption by mesenteric lymph node resection and lymph duct ligature 5 days prior to the experiments. Samples (blood, spleen and liver) were collected 2 hours after the inoculation and were cultured to recover bacteria of intestinal origin. One-half of the animals/group was observed to the mortality index. The groups (n = 20/group) were: BT group (BT-G); BT with lymphadenectomy (BTL-G); combination (C-G); and combination with lymphadenectomy (CL-G).

Results

BT was 100% positive in all groups. The BT index was similar between BT-G, BTL-G and CL-G (P = 0.6) and mortality was not observed in these groups, although a considerable amount of translocated bacteria could be recovered, particularly at the liver and spleen (Figure 1). When BT was added to the sepsis without lymph exclusion (C-G) the BT index was statistically lower (P = 0.04), but 50% (LD₅₀) of mortality occurred within 30 hours (Figure 1).

Conclusion

These results showed that, more than the amount of translocated bacteria, the gut-associated lymphoid system activation by the BT process played a pivotal role in the worsening of sepsis. Besides, BT occurred independently of mesenteric lymph interruption, showing that the hematological pathway of BT might be the principal route for bacterial dissemination into the bloodstream.