Some probiotics don't help C. diff diarrhoea

Jacob Collyer-Smith Lifestyle Writer

A new study1 carried out here in the UK has found that some strains of probiotics are ineffective at preventing antibiotic-associated diarrhoea (AAD) and C. difficile diarrhoea (CDD). At first reading, this may not sound like particularly positive news for the probiotics industry, but in actual fact it adds yet more credibility to the evidence of probiotic strain-specificity - find out more on our sister site, the Probiotics Learning Lab.

Published in Health Technology Assessment, from the UK's National Institute for Health Research, the study aimed to discover whether a probiotic combination containing L. acidophilus CUL60, L. acidophilus CUL21, B. bifidum CUL20, and B. lactis CUL34, could be effective in preventing AAD and CDD in hospital patients aged 65 years+. These probiotics strains are well researched for digestive and immune health, but little is known of their ability to prevent antibiotic-associated side effects.

doctor holding elderly patients hand

Elderly patients (65 years+) are at a high risk of suffering with antibiotic-associated side effects and C. difficile infections. NHS statistics reveal that this age group account for 75% of all C. difficile cases. This makes the search for an effective preventative measure a high priority, and the reason they were targeted by the researchers of this latest study. An effective preventative measure would dramatically increase the health of hospitalised elderly patients, as well as cutting the cost of treating them.

This latest study encompassed a total of 2,981 participants with a median age of 77 years, who were split into two groups to receive either the probiotic combination or placebo every day for the duration of 21 days. However, the results revealed that there was no significant difference between the two groups in terms of infection rates or the frequency and duration of gastrointestinal symptoms.

The authors concluded; "We found no evidence that probiotic administration was effective in preventing AAD. Although there was a trend towards reduced CDD in the probiotic arm, on balance, the administration of this probiotic seems unlikely to benefit older patients exposed to antibiotics." The researchers did concede that other strains of probiotics may prevent AAD and CDD more effectively, which previous studies certainly suggest.

One particular combination of probiotics, L. acidophilus Rosell-52 and L. rhamnosus Rosell-11, are extremely well researched in the prevention of antibiotic-associated diarrhoea and C. difficile diarrhoea. Another well noted probiotic strain in this area is Saccharomyces boulardii. Read more about these strains on the Probiotics Database.

As research continues to grow and we discover more and more probiotic strains, it is inevitable that along the way we will find some that are ineffective in certain areas of human health. The message that this latest research really reinforces is that different strains of probiotics have different qualities and characteristics and we should use them according to their specific strengths.

To find out more about strain specificity and why it's so important, see the following FAQ, over in the Probiotics Learning Lab:

Are all types (strains) of friendly bacteria the same?


  1.  Allen, S. et al (2013) A high-dose preparation of Lactobacilli and Bifidobacteria in the prevention of antibiotic-associated and Clostridium difficile diarrhoea in older people admitted to hospital: a multicentre, randomised, double-blind, placebo-controlled, parallel arm trial. Health Technology Assessment. 17, 57. Image source: