The contribution of sulphate reducing bacteria and 5-aminosalicylic acid to faecal sulphide in patients with ulcerative colitis.
BACKGROUND
Butyrate oxidation within the colonocyte is selectively inhibited by hydrogen sulphide, reproducing the metabolic lesion observed in active ulcerative colitis.


OBJECTIVE
To study generation of hydrogen sulphide by sulphate reducing bacteria (SRB) and the effects of 5-aminosalicylic acid (5-ASA) in patients with ulcerative colitis in order to identify a role of this noxious agent in pathogenesis.


METHODS
Fresh faeces were obtained from 37 patients with ulcerative colitis (23 with active disease) and 16 healthy controls.


METHODS
SRB were enumerated from fresh faecal slurries and measurements made of sulphate reducing activity, and sulphate and hydrogen sulphide concentrations. The effect of 5-ASA on hydrogen sulphide production was studied in vitro.


RESULTS
All controls and patients with active ulcerative colitis carried SRB and total viable counts were significantly related to the clinical severity grade. SRB were of two distinct types: rapidly growing strains (desulfovibrios) which showed high sulphate reduction rates, present in 30% of patients with ulcerative colitis and 44% of controls; and slow growing strains which had little activity. In vitro, 5-ASA inhibited sulphide production in a dose dependent manner; in patients with ulcerative colitis not on these drugs faecal sulphide was significantly higher than in controls (0.55 versus 0.25 mM, p=0.027).


CONCLUSIONS
Counts and carriage rates of SRB in faeces of patients with ulcerative colitis are not significantly different from those in controls. SRB metabolism is not uniform between strains and alternative sources of hydrogen sulphide production exist in the colonic lumen which may be similarly inhibited by 5-ASA. The evidence for hydrogen sulphide as a metabolic toxin in ulcerative colitis remains circumstantial.
Pitcher
M C
MC
MRC Dunn Clinical Nutrition Centre, Cambridge, UK.
Beatty
E R
ER
Cummings
J H
JH
D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D003093:Colitis, Ulcerative / Q000378:metabolism / Q000382:microbiology*; D004305:Dose-Response Relationship, Drug; D005243:Feces / Q000737:chemistry / Q000382:microbiology*; D005260:Female; D006801:Humans; D006862:Hydrogen Sulfide / Q000378:metabolism; D008297:Male; D019804:Mesalamine / Q000494:pharmacology*; D008875:Middle Aged; D013431:Sulfates / Q000378:metabolism; D016999:Sulfur-Reducing Bacteria / Q000254:growth & development / Q000378:metabolism*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D013431:Sulfates; D019804:Mesalamine; D006862:Hydrogen Sulfide