Do children's upper respiratory tract infections benefit from probiotics?

Background: The microbiota of the gastrointestinal tract have profound influence at multiple levels, even on the development and maintenance of lung immunity and inflammation. Aim of this review is to evaluate the current knowledge about the specific impact on children's respiratory tract infections from probiotics, live microbes with the power to modify intestinal microbial populations and exert subsequent benefits for the host. Discussion: The role of probiotics in gastrointestinal and allergic diseases has been largely assessed, but the number of studies performed so far in the field of respiratory tract infections is small, though some data show that probiotic administration might display clinical advantages. Probiotic strain identity and host genetic differences may account for differential modulation of immune responses by probiotics. Current laboratory and clinical data regarding the possibility of the role of probiotics on preventing the development of respiratory tract infections are contradictory, and are somewhat insufficient to recommend strongly their routine use. Further study of gastrointestinal-respiratory interactions is likely to yield important insights into the pathogenesis of different pulmonary diseases, and improve our knowledge in the prophylactic role of probiotics in children affected by recurrent upper respiratory tract infections. Summary: A better understanding of the effects of different probiotic strains and a deeper insight into their mechanisms of action are needed for the validation of specific strains carrying a potential to modify the frequency and severity of RTIs in infants and children. No data have been collected in pediatric patients with chronic underlying diseases, and yet there are no published data concerning treatment of RTIs with probiotics. The very few studies published so far do not indicate which micro-organism or administration regimen might exert beneficial effects as a prevention tool of RTIs both in healthy children and in those with recurrent RTIs. Further research to establish the role of probiotics in the treatment and prevention of RTIs, including those involving the lower respiratory tract, are required and should also clarify if any susceptible subgroups of respiratory diseases exist, and how these subgroups benefit from supplementation with certain probiotic strains.