Acute Infectious Diarrhea.

Acute infectious diarrhea (AID) is one of the most common diseases in pediatric age with relevant burden both in high and in low-income countries. Thanks to their direct action on enterocyte functions and indirect actions on the mucosal and systemic immune system and on intestinal microbiome, probiotics are an ideal intervention to treat AID in childhood. However, their efficacy is strictly related to strains and indications, and practitioners should take this information into account in clinical practice. This chapter summarizes the main mechanisms of action of probiotics in AID, with a focus on proof of efficacy supporting their use in prevention and treatment of childhood AID. The use of selected strains in appropriate doses is strongly recommended by guidelines of AID, based on compelling proofs of efficacy and safety. At present, therapy with probiotics of AID is probably the strongest indication for probiotic use in medicine. Their role in prevention of AID is however questionable in healthy population, whereas it should be considered in at-risk population. Evidence for prevention of diarrhea in day-care centers and communities is lacking, but consistent evidence supports efficacy in prevention of hospital acquired diarrhea. Finally, this chapter presents novelties on this topic, in particular the role of rotavirus immunization on probiotics effectiveness and the effect of probiotics and postbiotics on Covid-associated diarrhea.Overall: AID is the most convincing area for probiotic use in children with gastrointestinal disorders, and effective strains should be used early on after onset of symptoms.