Influence of intestinal flora on the development of fibrosis and cirrhosisin a rat model

Background and Aims: The gut flora play a significant role in the dispositi on of many foreign substances, as well as producing nutrients and toxins th at may be absorbed and reach the liver. This study examines the influence o f antibiotic-induced alterations in gut flora on the development of hepatic fibrosis in a rat model. Methods: Thirty-six male Porton rats were fed alcohol (3.9 g/kg per day) in the drinking water and exposed to carbon tetrachloride (CCl4) vapor (80 p. p.m.) for 6 h each night, five nights per week. Half were also given neomyc in (330 mg/kg per day) and polymyxin B (105 mg/kg per day) in the drinking water. Fecal cultures were carried out at 0, 3, 8 and 13 weeks; rats were k illed at 14 weeks. Coded liver section were assessed for fibrosis using a g raded scale (0, no abnormal fibrosis to 4, early or established cirrhosis). Results: Rats that received antibiotics had significantly higher fibrosis s cores than those that did not (mean score 2.4 vs 1.4, P < 0.01, ordinal log istic regression). Three rats, all of which were in the antibiotic group, w ere cirrhotic. Rats that had received antibiotics fell into three groups. F our had overgrowth of Proteus mirabilis; in these the fibrosis scores (mean 1.5) were similar to those in the rats that did not receive antibiotic. In six, no organisms could be cultured; fibrosis scores of these (mean 2.3) w ere slightly elevated (P = 0.03), but this was mainly because of a single r at in this subgroup being cirrhotic. The remaining eight had overgrowth of Morganella morganii; these had significantly (P < 0.001) elevated fibrosis scores. Furthermore, in this subgroup, fibrosis scores were significantly c orrelated (Spearman's r = 0.82, P = 0.01) with the number of weeks of Morga nella colonization. Conclusions: Antibiotic treatment exacerbated fibrosis in the alcohol/CCl4 rat model; this effect appeared to be related to the type of gut flora and may be endotoxin-mediated. (C) 2000 Blackwell Science Asia Pty Ltd.