The reduction of bile pigments by faecal and intestinal bacteria

The impact of intestinal microflora on serum bilirubin levels

“…In our in vitro studies no bilirubin-reducing activity was detected in various clostridial strains including C. pasteurianum, C. acetobutylicum, C. novyii, C. paraputrificum, C. sporogenes, C. bifermentans, C. scindens, C. hiranonis and C. sordelii (L. Vítek, unpublished results). Based on these limited data it seems that bilirubin reduction within gastrointestinal tract is confined to bacterial species of C. perfringens, C. difficile, C. ramosum and possibly B. fragilis [2,7,8].…”

“…fragilis [8] despite the fact that hundreds of different indigenous microbial strains inhabit human gastrointestinal tract [9]. These organisms are capable of carrying out many enzymatic reactions that the host human cells cannot catalyze.…”

Identification of bilirubin reduction products formed by Clostridium perfringens isolated from human neonatal fecal flora

“…Under normal conditions only small amounts of bilirubin can be found in stools of adults (5-20 mg/day) while urobilinoids are predominant bile pigments (50-250 mg/day) [2]. Nevertheless, only few bacterial strains have been isolated, that are unequivocally capable of reduction of bilirubin to urobilinogens: Clostridium ramosum [5], Clostridium perfringens and Clostridium difficile [1] and Bacteroides fragilis [6]. Previously, such catalytic activity had been already suggested to be an attribute of the Clostridium genus [7][8][9].…”

Intestinal flora and bilirubin

“…Most of the deconjugation occurs in the distal ileum and colon where anaerobic Clostridia sp. and Bacteroides fragilis not only hydrolyze the bilirubin conjugates but also reduce (hydrogenate) the resultant UCB to colorless urobilinoids [5,6]. It is probable that anaerobic bacteria can synthesize urobilinoids only from UCB, so that deconjugation is an obligatory preceding step [5][6][7].…”

“…Among the more than 400 bacterial strains present in the gut of a healthy adult man [10], only 4 strains so far have been found capable of deconjugating bilirubin and reducing the UCB to urobilinoids: Clostridiun ramosum [7], Clostridium perfringens and difficile [8], and Bacteriodes fragilis [6]. Escherichia coli, which is a dominant organism in the more proximal small bowel shows a b-glucuronidase activity more that 30 times lower than C. perfringens [11].…”