{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T19:46:31Z","timestamp":1767901591344,"version":"3.49.0"},"reference-count":90,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2021,2,22]],"date-time":"2021-02-22T00:00:00Z","timestamp":1613952000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Microorganisms"],"abstract":"<jats:p>Respiratory tract infections (RTIs) are common in childhood because of the physiologic immaturity of the immune system, a microbial community under development in addition to other genetic, physiological, environmental and social factors. RTIs tend to recur and severe lower viral RTIs in early childhood are not uncommon and are associated with increased risk of respiratory disorders later in life, including recurrent wheezing and asthma. Therefore, a better understanding of the main players and mechanisms involved in respiratory morbidity is necessary for a prompt and improved care as well as for primary prevention. The inter-talks between human immune components and microbiota as well as their main functions have been recently unraveled; nevertheless, more is still to be discovered or understood in the above medical conditions. The aim of this review paper is to provide the most up-to-date overview on dysbiosis in pre-school children and its association with RTIs and their complications. The potential role of non-harmful bacterial-derived products, according to the old hygiene hypothesis and the most recent trained-innate immunity concept, will be discussed together with the need of proof-of-concept studies and larger clinical trials with immunological and microbiological endpoints.<\/jats:p>","DOI":"10.3390\/microorganisms9020448","type":"journal-article","created":{"date-parts":[[2021,2,22]],"date-time":"2021-02-22T20:42:51Z","timestamp":1614026571000},"page":"448","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Dysbiosis in Pediatrics Is Associated with Respiratory Infections: Is There a Place for Bacterial-Derived Products?"],"prefix":"10.3390","volume":"9","author":[{"given":"Stefania","family":"Ballarini","sequence":"first","affiliation":[{"name":"Department of Experimental Medicine, University of Perugia, Didactic Pole \u201cSant\u2019Andrea delle Fratte\u201d, 06132 Perugia, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Giovanni A.","family":"Rossi","sequence":"additional","affiliation":[{"name":"Unit of Pediatric Pulmonary, G. Gaslini University Hospital, 16147 Genoa, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3468-5568","authenticated-orcid":false,"given":"Nicola","family":"Principi","sequence":"additional","affiliation":[{"name":"Universit\u00e0 degli Studi di Milano, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Susanna","family":"Esposito","sequence":"additional","affiliation":[{"name":"Department of Medicine and Surgery, Pediatric Clinic, University of Parma, 43126 Parma, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"139","DOI":"10.1111\/j.1440-1754.2007.01033.x","article-title":"Occurrence and management of acute respiratory illnesses in early childhood","volume":"43","author":"Kusel","year":"2007","journal-title":"J. Paediatr. 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