Probiotics for the Prevention and Treatment of Clostridium difficile in Older Patients

Jasmin Islam; Jonathan Cohen; Chakravarthi Rajkumar; Martin J. Llewelyn


Age Ageing. 2012;41(6):706-711. 

In This Article

Probiotics: Nomenclature and Mechanisms of Action

The term probiotic refers to live micro-organisms which when administered in adequate amounts confer a health benefit to the host. In 2002, the Food and Agricultural Organisation and World Health Organisation released guidelines outlining requirements for probiotic classification (summarised in Figure 1). The probiotic effect may be strain-specific, and correct naming of a probiotic strain frequently includes the gene and species (e.g. Lactobacillus rhamnosus) and a specific strain-identifying name. Of note, the term prebiotic refers to non-digestible food ingredients consumed with the aim of stimulating the growth or activity of bacteria in the gastrointestinal tract and some products containing pro- and prebiotics are marketed and termed synbiotics.

Figure 1.

Guidelines for the evaluation of probiotics adapted from the joint FAO/WHO guidelines [53].

The majority of probiotics studied are species of Lactobacillus and Bifidobacterium, both of which are part of the normal gut flora. However, one of the first strains described was E. coli Nissle 1917 which was identified in the stool of a soldier who survived an outbreak of dysentery in the First World War. The yeast Saccharomyces boulardii has also been studied extensively. It is not part of the human gut flora but colonises the skin of fruit such as lychees.

Although use of probiotics has been described in a wide range of conditions including atopy and bacterial vaginosis, the great majority of experience relates to gastro-intestinal disease, particularly in children. A range of potential mechanisms for the beneficial effects of probiotics have been proposed. These include stabilisation of epithelial tight junctions, action of bacteriocins, immunomodulation and modulation of cell signalling pathways, displacement of pathogenic bacteria from the epithelial surface, alteration of gut pH by fermentation and induction of opioid and cannabinoid receptors.[24]

Saccharomyces boulardii may have specific beneficial properties. In particular, it secretes a protease that hydrolyses Toxin A and appears to induce a range of anti-inflammatory responses and secretion of IgA, including IgA specific for C. difficile toxin into the colon. These properties have been reviewed by Pothoulakis.[25]