Traditional probiotics have a long history of safe use and most strains are considered having no pathogenic potential.There is a growing interest in the cultivation of new and more active strains.But it can not be assumed that these novel probictic organisms share the historical safety of the traditional strains.Recently,attention has been focused on a number of reports of human infections caused by probiotic.Probiotics may theoretically be responsible for four types of side effects:systematic infections,deleterious metabolic activities,excessive immune stimulation in susceptible individuals,and antibiotics resistance gene transfer.So the use of new strains of probiotics should be carefully assessed and tested for its safety.