Comprehensive approaches for assessing the safety of probiotic bacteria

Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. Among the different microbial types, lactobacilli have been explored most extensively as potential therapeutics in human health. Lactobacilli belong to the human normal microbiota of the gastro-intestinal and urogenital tracts and have been traditionally used as starter cultures in the preparation of fermented foods. They are considered extremely safe as compared to pharmacological agents since there have been very rare reports of any adverse effects. However, the safety of probiotics is of paramount importance as new strains are continuously evolving and being commercialized. The introduction of a new probiotic strain demands that it is at least as safe as its conventional counterparts. The newly emerging strains of probiotic lactobacilli with specific health claims may not necessarily have a documented history of safe use, hence, their safety is a matter of great concern from public health perspective. Moreover, it is now well recognized that the specific health claims associated with probiotics are highly strain specific, therefore, their safety needs to be assessed very comprehensively at strain level on case to case basis. Hence, an attempt have been made in this review to focus, at the preclinical level, on the various in vitro and in vivo tests using appropriate animal models, for assessing the safety and toxicity of probiotic organisms with a special emphasis on lactobacilli.