A survey on established and novel strains for probiotic applications

Probiotics are a heterogeneous group of non pathogenic bacteria that are functionally defined by their ability to produce a health benefit to the host when provided in adequate amounts. In recent years, a number of rigorous studies based on double blind randomized placebo-controlled human intervention trials using established probiotics have been carried out, better supporting the idea that our health can be positively affected by the regular administration of specific strains. In the meantime, there is an interest in selecting novel candidate probiotic strains for particular subject groups. In this survey, we focused on both aspects and therefore literature data was collected and analysed (297 papers) for the strains which were applied in clinical trials in the last fi ve years (2008–2013). Information on the identity of the strain, strain identification number and the kind of application were extracted and presented, to show that only a limited number of species includes the majority of probiotic strains. Also, systematic reviews within the Cochrane Library were analyzed and diseases treated were grouped according to the categories proposed on ClinicalTrials.gov website (http://www.clinicaltrials.gov/), i.e., macro areas following the human organ or system involved. Besides the standard use of alive bacterial cells to be ingested, literature data on health benefits deriving from inactivated bacterial cells have been reported and are summarized. Also, not all the strains proved to be effective for some diseases, confirming that beneficial properties are strain and application dependent. Finally, the perspectives in the field of probiotics brought about genomics are briefly reviewed.