Probiotics and safety

Bacterial species that have traditionally been regarded as safe are used in probiotics; the main strains used include lactic acid bacteria and bifidob acteria that inhabit the intestinal tracts of humans and animals. However, reports of frequent isolation of bacteria used in probiotics from infection sources in recent years have raised much debate over the safety of probiot ics. This article describes the status quo of isolation of probiotic bacter ia from infections and reviews each of the factors that have to be addresse d in assessing the safety of probiotics, namely pathogenicity, infectivity, toxicity, and intrinsic properties of the bacteria. Monoassociation with B ifidobacterium longum in gnotobiotic mice as a method to assess safety with respect to infection, and translocation and immune responses as a result o f the monoassociation are also described.