{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"medRxiv"}],"indexed":{"date-parts":[[2026,2,21]],"date-time":"2026-02-21T05:59:41Z","timestamp":1771653581566,"version":"3.50.1"},"posted":{"date-parts":[[2026,2,18]]},"group-title":"Dermatology","reference-count":11,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,2,18]],"date-time":"2026-02-18T00:00:00Z","timestamp":1771372800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.medrxiv.org\/about\/FAQ#license"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,2,18]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  <jats:italic>Staphylococcus aureus<\/jats:italic>\n                  plays a central role in the exacerbation of atopic dermatitis (AD), but the population structure and pathogenic determinants of strains colonizing AD patients remain poorly understood. It is unclear whether these strains mirror those circulating in the general community or whether specific clonal lineages are selectively adapted to the AD skin microenvironment. Data addressing this question are scarce, particularly in Portugal. In this study, we investigated the molecular epidemiology and pathogenic traits of\n                  <jats:italic>S. aureus<\/jats:italic>\n                  colonizing skin lesions in adult patients with AD in Portugal. We found that lesion-associated isolates belonged predominantly to the methicillin-susceptible\n                  <jats:italic>S. aureus<\/jats:italic>\n                  MSSA-ST398 clonal type, a lineage that is widely circulating in the Portuguese community, particularly among vulnerable populations, and that has also been implicated in severe human infections. Notably, isolates from this clonal type in AD harboured specific pathogenicity traits associated with skin barrier disruption, including hemolysin and urease production, which may contribute to their success as colonizers in AD. Our findings highlight that\n                  <jats:italic>S. aureus<\/jats:italic>\n                  colonization in AD arises from a dynamic interplay between community-level molecular epidemiology and disease-specific selective pressures. While circulating lineages provide the genetic background diversity, the AD skin microenvironment appears to shape which clones ultimately become dominant. Such an integrated perspective may help to inform future geographically tailored strategies aimed at limiting bacterial burden and preventing disease exacerbation in AD.\n                <\/jats:p>","DOI":"10.64898\/2026.02.17.26346495","type":"posted-content","created":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T00:40:13Z","timestamp":1771461613000},"source":"Crossref","is-referenced-by-count":0,"title":["Methicillin-Susceptible\n                  <i>Staphylococcus aureus<\/i>\n                  ST398 in atopic dermatitis in Portugal displays pathogenic traits associated with impaired skin barrier function"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8637-6778","authenticated-orcid":false,"given":"Diana","family":"Caieiro","sequence":"first","affiliation":[{"name":"Laboratory of Bacterial Evolution and Molecular Epidemiology, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica Ant\u00f3nio Xavier, Universidade Nova de Lisboa, Oeiras, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3762-9809","authenticated-orcid":false,"given":"Nuno A.","family":"Faria","sequence":"additional","affiliation":[{"name":"Laboratory of Bacterial Evolution and Molecular Epidemiology, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica Ant\u00f3nio Xavier, Universidade Nova de Lisboa, Oeiras, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2855-8404","authenticated-orcid":false,"given":"Ana","family":"Botelho","sequence":"additional","affiliation":[{"name":"Laboratory of Bacterial Evolution and Molecular Epidemiology, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica Ant\u00f3nio Xavier, Universidade Nova de Lisboa, Oeiras, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3320-868X","authenticated-orcid":false,"given":"Mariana","family":"Ara\u00fajo","sequence":"additional","affiliation":[{"name":"Laboratory of Bacterial Evolution and Molecular Epidemiology, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica Ant\u00f3nio Xavier, Universidade Nova de Lisboa, Oeiras, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5758-0339","authenticated-orcid":false,"given":"Leonor","family":"Ramos","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Coimbra University Hospital, Unidade Local de Sa\u00fade de Coimbra, Coimbra, Portugal"},{"name":"Faculty of Medicine, University of Coimbra, Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1161-269X","authenticated-orcid":false,"given":"Joana","family":"Calv\u00e3o","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Coimbra University Hospital, Unidade Local de Sa\u00fade de Coimbra, Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6842-1360","authenticated-orcid":false,"given":"Margarida","family":"Gon\u00e7alo","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Coimbra University Hospital, Unidade Local de Sa\u00fade de Coimbra, Coimbra, Portugal"},{"name":"Faculty of Medicine, University of Coimbra, Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1323-7184","authenticated-orcid":false,"given":"Maria","family":"Miragaia","sequence":"additional","affiliation":[{"name":"Laboratory of Bacterial Evolution and Molecular Epidemiology, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica Ant\u00f3nio Xavier, Universidade Nova de Lisboa, Oeiras, Portugal"}]}],"member":"54368","reference":[{"issue":"5","key":"2026022021001415000_2026.02.17.26346495v1.1","first-page":"359","article-title":"Genetic lineages and antimicrobial resistance genotypes in Staphylococcus aureus from children with atopic dermatitis: detection of clonal complexes CC1, CC97 and CC398","volume":"28","year":"2015","journal-title":"J. Chemother"},{"key":"2026022021001415000_2026.02.17.26346495v1.2","doi-asserted-by":"crossref","unstructured":"Chehadeh C , Nakatsuji T , Gallo RL . Staphylococcus aureus in atopic dermatitis: How a common bacterium exploits and drives disease. J. Allergy Clin. Immunol. 2026;S0091-6749","DOI":"10.1016\/j.jaci.2025.12.1009"},{"issue":"11","key":"2026022021001415000_2026.02.17.26346495v1.3","doi-asserted-by":"crossref","first-page":"2037","DOI":"10.1007\/s10096-019-03638-4","article-title":"Staphylococcus aureus nasal carriage among homeless population in Lisbon, Portugal","volume":"38","year":"2019","journal-title":"Eur. J. Clin. Microbiol. Infect. Dis. European Journal of Clinical Microbiology & Infectious Diseases"},{"key":"2026022021001415000_2026.02.17.26346495v1.4","first-page":"e00208","article-title":"Urease promotes pH homeostasis and growth of Staphylococcus aureus in skin-like conditions","volume":"0","year":"2025","journal-title":"J Bacteriol. American Society for Microbiology"},{"issue":"3","key":"2026022021001415000_2026.02.17.26346495v1.5","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1089\/mdr.2023.0219","article-title":"The changing epidemiology and antimicrobial susceptibility in a university hospital from Argentina","volume":"30","year":"2024","journal-title":"Microb. Drug Resist"},{"issue":"4","key":"2026022021001415000_2026.02.17.26346495v1.6","doi-asserted-by":"crossref","first-page":"506","DOI":"10.1159\/000515235","article-title":"Temporal variation in Staphylococcus aureus Protein A genotypes from nose and skin in atopic dermatitis patients","volume":"237","year":"2021","journal-title":"Dermatology"},{"issue":"4","key":"2026022021001415000_2026.02.17.26346495v1.7","first-page":"397","article-title":"Methicilin-susceptible Staphylococcus aureus clonal complex 398: An unusual agent of necrotizing pneumonia","volume":"30","year":"2024","journal-title":"Pulmonology. Elsevier Espana, S.L"},{"issue":"6","key":"2026022021001415000_2026.02.17.26346495v1.8","first-page":"e606","volume-title":"The Lancet Microbe","volume":"5","year":"2024"},{"key":"2026022021001415000_2026.02.17.26346495v1.9","first-page":"100222","article-title":"Biofilm Staphylococcus aureus colonizing the skin microbiota of adults with severe atopic dermatitis exhibits genomic diversity and convergence in biofilm traits","volume":"8","year":"2024","journal-title":"Biofilm. Elsevier B.V"},{"key":"2026022021001415000_2026.02.17.26346495v1.10","doi-asserted-by":"publisher","DOI":"10.1111\/bjd.14566"},{"issue":"2","key":"2026022021001415000_2026.02.17.26346495v1.11","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1016\/j.micinf.2010.10.023","article-title":"Identification of major clonal complexes and toxin producing strains among Staphylococcus aureus associated with atopic dermatitis","volume":"13","year":"2011","journal-title":"Microbes Infect. Elsevier Masson SAS"}],"container-title":[],"original-title":[],"link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.64898\/2026.02.17.26346495","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,2,21]],"date-time":"2026-02-21T05:00:23Z","timestamp":1771650023000},"score":1,"resource":{"primary":{"URL":"http:\/\/medrxiv.org\/lookup\/doi\/10.64898\/2026.02.17.26346495"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,18]]},"references-count":11,"URL":"https:\/\/doi.org\/10.64898\/2026.02.17.26346495","relation":{},"subject":[],"published":{"date-parts":[[2026,2,18]]},"subtype":"preprint"}}