The infection that looks exactly like a flare

Clostridioides difficile — C. difficile, or C. diff — is a spore-forming, anaerobic bacterium. It can produce up to three toxins: toxin A, toxin B, and in some strains a binary toxin. The toxins do the damage. The spores explain nearly everything else about how it behaves.

Spores travel by the faecal-oral route and germinate in the presence of primary bile salts when they reach the small intestine. A settled gut population normally stops them establishing. Alter that population — most often with a course of antibiotics — and the bacterium can colonise the colon and start producing toxin. That is why this is the infection that follows antibiotics.

Why inflammatory bowel disease changes the odds

People with inflammatory bowel disease have a four- to five-fold higher risk of developing it than the general population. The risk is not spread evenly. It has been consistently more frequent in ulcerative colitis than in Crohn’s, at roughly two to three times the risk. What seems to matter most is whether the colon is involved. People with colonic involvement were more likely to develop it, at odds of 2.2. An American Gastroenterological Association practice update puts colon-involving inflammatory bowel disease at an eightfold greater risk than the general population.

The other thing that shifts is the profile of who gets it. More than 40 percent of episodes in people with inflammatory bowel disease were community-acquired. The review reads that as disease-related vulnerability and immunosuppressive therapy mattering more than exposure to hospitals. Not having been in hospital, and not having taken an antibiotic recently, does not rule it out the way it might for somebody else.

The part that makes it dangerous

Diarrhoea, urgency, blood, cramping abdominal pain, fever. That list is the infection and it is also a flare, which is the whole problem. The two presentations overlap, and the infection can sit alongside a flare rather than instead of it. So the review concludes that people with inflammatory bowel disease must be routinely checked for it. The practice update says the same thing as an instruction to clinicians: test patients who present with a flare.

What it costs when it is missed

The infection in inflammatory bowel disease is consistently associated with worse outcomes: prolonged hospital stays, higher colectomy rates, and increased in-hospital mortality. The mortality is reported at odds of 3.9 in ulcerative colitis and 1.66 in Crohn’s. It also comes back more often: the RECIDIVISM study reported a 32 percent recurrence rate in people with inflammatory bowel disease against 24 percent in those without.