Expert commentary: Probiotics and respiratory tract infections

Probiotics are live microorganisms which can confer a health benefit on the host, when administered in adequate amounts. There is increasing evidence that probiotics are able to influence immune response in different sites including the respiratory mucosa. It is not yet known how bacteria modulate immune responses at distant tissue sites but it could depend on the existence of what has been called the “common mucosal immune system," which explains how activated lymphocytes can reach different mucosal sites. In this chapter we have analyzed some reviews regarding the role of probiotics in respiratory diseases. To date there is a weak evidence of the efficacy of probiotics in preventing the upper respiratory tract infections, even if it is not yet clear what is the probiotic strain that is needed to be used, the dosage and the duration of the therapy. Anyway, all studies agree on the need for a greater uniformity of the trials in order to obtain clearer guidance and safer conclusions.