RESUMEN
The establishment of balanced intestinal microbial flora bears importance in maintaining the well-being of the human host. In this context, probiotics improving the intestinal microflora confer a beneficial effect on human health when ingested as live microorganisms. Bifidobacterium and Lactobacillus are mainly used as probiotics in the pharmaceuticals or functional foods. On review of the papers published in the scientific journals, prophylactic use of probiotics was promising in reducing both the incidence and severity of necrotizing enterocolitis in preterm neonates, alleviating rotavirus infection and preventing the atopy symptoms in children. The efficacy of the probiotics with respect to the inflammatory disease such as Crohn's disease and ulcerative colitis are being studied. Analysis of the various cytokines and immune markers are being conducted to understand the mechanism of action of the probiotics related to allergy and inflammation. More clinical studies are needed based on appropriate and well-conducted trials with known strains and doses since the efficacy varies depending on the specific probiotic strains or doses. Some of the species or strains distributed in probiotic markets raised some safety concerns such as causing human infections or transmitting antibiotic resistance genes. Therefore continued efforts to improve strain characteristics with respect to the efficacy through evidence-based human studies and evaluation of the safety are desired.