{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T04:46:27Z","timestamp":1776746787463,"version":"3.51.2"},"reference-count":46,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T00:00:00Z","timestamp":1776729600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Secondary Lactose intolerance (SLI) is common among infants in China, primarily resulting from secondary lactase deficiency due to mucosal damage. Current diagnostic methods are limited by poor sensitivity and specificity.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To investigate gut microbial composition and metabolic dysfunction in infants with SLI and to explore the potential utility of residual fecal lactose as a non-invasive indicator related to SLI.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      SLI infants exhibited significantly higher residual fecal lactose and lactate levels accompanied by reduced fecal short-chain fatty acid (SCFA) availability, consistent with incomplete lactose digestion and altered microbial fermentation. Microbiota profiling revealed marked depletion of\n                      <jats:italic>Bacteroidetes<\/jats:italic>\n                      and certain\n                      <jats:italic>Firmicutes<\/jats:italic>\n                      (e.g.\n                      <jats:italic>Ruminococcaceae, Erysipelotrichaceae, Peptostreptococcaceae, Megasphaera<\/jats:italic>\n                      ), along with reduced glycolysis pathways.\n                      <jats:italic>In vitro<\/jats:italic>\n                      fermentation assays demonstrated a consistent reduction in total acid, acetate, and propionate production across multiple media, while lactate and gas production were significantly elevated in SLI samples under lactose, FOS, GOS, and starch-enriched conditions. Butyrate synthesis was partially preserved under protein-rich or minimal carbon media, indicating selective resilience of butyrogenic pathways. Microbial \u03b2-diversity analysis confirmed structural dysbiosis, with increased abundance of gas-associated taxa, including Clostridium.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Residual fecal lactose, when interpreted alongside microbial and metabolic profiles, may serve as a non-invasive indicator associated with secondary lactose intolerance in infants. These findings delineate microbiota\u2013metabolism features consistent with SLI pathophysiology and provide a conceptual framework for future validation studies and the development of nutritional or probiotic interventions.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fimmu.2026.1711945","type":"journal-article","created":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T04:22:39Z","timestamp":1776745359000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Diagnostic and metabolic insights into secondary lactose intolerance in infants via fecal lactose quantification and gut microbiome profiling"],"prefix":"10.3389","volume":"17","author":[{"given":"Jian","family":"Kuang","sequence":"first","affiliation":[{"name":"State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Institute of Food Science, Zhejiang Academy of Agricultural 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