{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,29]],"date-time":"2026-10-29T00:05:04Z","timestamp":1793232304679,"version":"4.5.0"},"reference-count":56,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,3]],"date-time":"2026-07-03T00:00:00Z","timestamp":1783036800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100019412","name":"Bursa Uluda\u011f \u00dcniversitesi","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100019412","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Cell. Infect. Microbiol."],"abstract":"<jats:p>\n                    Atlantic bluefin tuna (ABFT;\n                    <jats:italic>Thunnus thynnus<\/jats:italic>\n                    ) is among the most valuable commodities in Mediterranean mariculture, and recent increases in seawater temperatures have coincided with the re-emergence of bacterial diseases causing catastrophic losses. During the summer 2025 mortality event, we investigated stranded and moribund ABFT using bacteriological isolation and identification, high-throughput 16S amplicon profiling of tissue-associated bacterial communities, whole-genome sequencing to resolve a complete genome of the etiologic agent, transmission electron microscopy, and gross and histopathological examinations. Across multiple organs, the metagenomic profiles were overwhelmingly dominated by\n                    <jats:italic>Lactococcus garvieae<\/jats:italic>\n                    , supporting a primary systemic bacterial etiology. The isolate displayed a capsulated phenotype, and genome analysis identified a capsule-associated gene cluster consistent with a capsulated lineage. Capsule expression was further confirmed ultrastructurally by transmission electron microscopy. Pathology indicated fulminant septicemia with prominent hemorrhagic lesions and severe cardioperitoneal involvement, including fibrinous epicarditis with abundant Gram-positive cocci, alongside marked hepatic and splenic pathology. Collectively, these data document, for the first time in two decades, the detection of a capsulated\n                    <jats:italic>L. garvieae<\/jats:italic>\n                    serotype or lineage associated with ABFT mass mortality. Rapid etiologic confirmation, mitigation of temperature-related and husbandry-associated stress, and targeted prevention strategies (including vaccination and biosecurity) are recommended to reduce recurrence in warming coastal waters.\n                  <\/jats:p>","DOI":"10.3389\/fcimb.2026.1831351","type":"journal-article","created":{"date-parts":[[2026,7,3]],"date-time":"2026-07-03T05:41:23Z","timestamp":1783057283000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":1,"title":["Capsulated Lactococcus garvieae caused devastating mortality in Atlantic bluefin tuna, Thunnus thynnus: genomic and histopathologic characterization"],"prefix":"10.3389","volume":"16","author":[{"given":"Muhammed","family":"Duman","sequence":"first","affiliation":[{"name":"Department of Aquatic Animal Diseases, Faculty of Veterinary Medicine, Bursa Uludag University","place":["Bursa, T\u00fcrkiye"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Abigail","family":"Armwood","sequence":"additional","affiliation":[{"name":"Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University","place":["Raleigh, NC, United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nihed","family":"Ajmi","sequence":"additional","affiliation":[{"name":"Department of Aquatic Animal Diseases, Faculty of Veterinary Medicine, Bursa Uludag University","place":["Bursa, T\u00fcrkiye"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"G\u00f6rkem","family":"Ta\u015f\u00e7\u0131","sequence":"additional","affiliation":[{"name":"Department of Aquatic Animal Diseases, Faculty of Veterinary Medicine, Bursa Uludag University","place":["Bursa, T\u00fcrkiye"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David","family":"Speare","sequence":"additional","affiliation":[{"name":"Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island","place":["Charlottetown, PE, Canada"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"\u00d6zkan","family":"Yava\u015f","sequence":"additional","affiliation":[{"name":"Department of Pathology, Faculty of Veterinary Medicine, Bursa Uludag University","place":["Bursa, T\u00fcrkiye"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Izzet Burcin","family":"Saticioglu","sequence":"additional","affiliation":[{"name":"Department of Aquatic Animal Diseases, Faculty of Veterinary Medicine, Bursa Uludag University","place":["Bursa, T\u00fcrkiye"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,7,3]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1016\/j.aquaculture.2024.741887","article-title":"Comparative proteomic and genomic analysis of Lactococcus garvieae and Lactococcus petauri isolates from Turkey","volume":"596","author":"Altun","year":"2025","journal-title":"Aquaculture"},{"key":"B2","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1016\/B978-0-12-411459-3.00008-4","article-title":"Diseases in tuna aquaculture","volume-title":"Adv. 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