Abstract
Traditionally probiotics are defined as viable microorganisms (bacteria or yeasts) that have a beneficial effect on the health of the host. Probiotics are used in fermented dairy products, but also in other foods, clinical foods and pharmaceutical preparations and they are also increasingly used as added functional ingredients in non-fermented foods. The selection of new probiotic organisms targets on new strains and even genera that are more beneficial organisms or specific. When totally novel microbes and genetically modified organisms are introduced, their safety and the risk-to-benefit ratio have to be carefully studied and assessed. Also, new probiotics should be of genera and strains commonly found in the healthy human intestinal microflora. Lactic acid bacteria in foods have a long history of safe use. Members of the genera Lactococcus and Lactobacillus are most commonly regarded as having the generally recognised safe status. Members of the genera Streptococcus and Enterococcus and also other genera of lactic acid bacteria include some opportunistic pathogens. The theoretical adverse effects of probiotics including potential acute effects, strain-dependent properties, intrinsic factors and the potential virulence are discussed. The available information supports the safety of currently used probiotics, but recommendations for the safety assessment of new probiotics are needed and proposed.