Mucolytic bacteria with increased prevalence in IBD mucosa augment in vitro utilization of mucin by other bacteria.
OBJECTIVE
Mucosa-associated bacteria are increased in inflammatory bowel disease (IBD), which suggests the possibility of an increased source of digestible endogenous mucus substrate. We hypothesized that mucolytic bacteria are increased in IBD, providing increased substrate to sustain nonmucolytic mucosa-associated bacteria.


METHODS
Mucolytic bacteria were characterized by the ability to degrade human secretory mucin (MUC2) in pure and mixed anaerobic cultures. Real-time PCR was used to enumerate mucosa-associated mucolytic bacteria in 46 IBD and 20 control patients. Bacterial mucolytic activity was tested in vitro using purified human MUC2.


RESULTS
We confirm increased total mucosa-associated bacteria 16S rRNA gene in macroscopically and histologically normal intestinal epithelium of both Crohn's disease (CD) (mean 1.9-fold) and ulcerative colitis (UC) (mean 1.3-fold). We found a disproportionate increase in some mucolytic bacteria. Mean Ruminococcus gnavus were increased >4-fold and Ruminococcus torques ∼100-fold in macroscopically and histologically normal intestinal epithelium of both CD and UC. The most abundantly detected mucolytic bacterium in controls, Akkermansia muciniphila, was reduced many fold in CD and in UC. Coculture of A. muciniphila with MUC2 as the sole carbon source led to reduction in its abundance while it augmented growth of other bacteria.


CONCLUSIONS
Mucolytic bacteria are present in healthy humans, where they are an integral part of the mucosa-associated bacterial consortium. The disproportionate increase in R. gnavus and R. torques could explain increased total mucosa-associated bacteria in IBD.
Png
Chin Wen
CW
Mater Medical Research Institute and Department of Medicine, University of Queensland, Mater Health Services, South Brisbane, Queensland, Australia.
Lindén
Sara K
SK
Gilshenan
Kristen S
KS
Zoetendal
Erwin G
EG
McSweeney
Chris S
CS
Sly
Lindsay I
LI
McGuckin
Michael A
MA
Florin
Timothy H J
TH
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003106:Colon / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000235:genetics / Q000382:microbiology* / Q000473:pathology; D007413:Intestinal Mucosa / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009077:Mucins / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D045857:Ruminococcus / Q000235:genetics* / Q000378:metabolism
D009077:Mucins