COMPOSITION AND DIVERSITY OF INTESTINAL COLIFORM FLORA INFLUENCE BACTERIAL TRANSLOCATION IN RATS AFTER HEMORRHAGIC STRESS

Coliform bacteria are the most frequently reported bacteria to translo cate after hemorrhage. We investigated the correlation between composi tion and diversity of the cecal coliform flora and the degree of trans location in a rat model of hemorrhagic stress. Two groups of nine rats each were bled to 60 and 50 mm Hg mean arterial blood pressure, respe ctively. A sham-operated group without bleeding (n = 9) and a noninstr umented group (n = 6) served as controls. From each rat, 40 coliform i solates from the cecum and up to 16 from positive mesenteric lymph nod e (MLN) cultures were tested with an automated biochemical fingerprint ing method. The phenotypic diversity of coliforms in each cecal sample was calculated as Simpson's diversity index (DI), and similarities be tween bacterial types in different samples were calculated as populati on similarity coefficients. Three rats in the sham-operated group and seven in each of the bled groups showed bacterial translocation. Of th e different biochemical phenotypes (BPTs) found in the cecum of bled r ats (mean, 6.5 BPTs), only a few were detected in MLNs (mean, 1.9 BPTs per MLN), with Escherichia coli being the dominant species. The trans locating E. coli strains were mainly of two BPTs. Rats showing no tran slocation either did not carry these strains or had a high diversity o f coliforms in the cecum. Furthermore, translocation of these coliform types was independent of their proportion in the cecum. In bled rats, the diversity of coliforms (mean DI, 0.53) was significantly higher t han that in control groups (mean DI, 0.30; P = 0.004), suggesting that hemorrhage stimulates an increase in diversity of cecal coliforms. Ra ts with similar coliform flora and subjected to the same treatment sho wed similar patterns of translocation. Our results suggest that the co mposition of the coliform flora is an important factor in translocatio n and that certain coliform strains have the ability to translocate an d survive in MLNs more easily than others.