Failure of dietary oligofructose to prevent antibiotic-associated diarrhoea

Background: Oligofructose is metabolized by bifidobacteria, increasing their numbers in the colon. High bifidobacteria concentrations are important in providing 'colonization resistance' against pathogenic bacteria. Aim: To reduce the incidence of antibiotic-associated diarrhoea in elderly patients. Methods: Patients over the age of 65 taking broad-spectrum antibiotics received either oligofructose or placebo. A baseline stool sample was cultured for Clostridium difficile and tested for C. difficile toxin. A further stool sample was analysed for C. difficile if diarrhoea developed. Results: No difference was seen in the baseline characteristics, incidence of diarrhoea, C. difficile infection or hospital stay between the two groups (n = 435). Oligofructose increased bifidobacterial concentrations (P < 0.001, 95% CI: 0.69-1.72). A total of 116 (27%) patients developed diarrhoea of which 49 (11%) were C. difficile-positive and were more likely to be taking a cephalosporin (P = 0.006), be female (P < 0.001), to have lost more weight (P < 0.001, 95% CI: 0.99-2.00) and stayed longer in hospital (P < 0.001, 95% CI: 0.10-1.40). Amoxicillin (amoxycillin) and clavulanic acid increased diarrhoea not caused by C. difficile (P = 0.006). Conclusion: Oligofructose does not protect elderly patients receiving broad-spectrum antibiotics from antibiotic-associated diarrhoea whether caused by C. difficile or not. Oligofructose was well-tolerated and increased faecal bifidobacterial concentrations.