{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T13:10:54Z","timestamp":1788959454891,"version":"build-2803163510"},"reference-count":90,"publisher":"American Society for Microbiology","issue":"9","license":[{"start":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T00:00:00Z","timestamp":1788912000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T00:00:00Z","timestamp":1788912000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"DOI":"10.13039\/100000060","name":"National Institute of Allergy and Infectious Diseases","doi-asserted-by":"publisher","award":["R01AI164712"],"award-info":[{"award-number":["R01AI164712"]}],"id":[{"id":"10.13039\/100000060","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000057","name":"National Institute of General Medical Sciences","doi-asserted-by":"publisher","award":["T32GM008111"],"award-info":[{"award-number":["T32GM008111"]}],"id":[{"id":"10.13039\/100000057","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["mBio"],"published-print":{"date-parts":[[2026,9,9]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      Neonatal infection is a leading cause of morbidity and mortality worldwide, particularly among preterm and low birth weight infants. Probiotic bacteria are widely used in peri- and postnatal care and can reduce neonatal intestinal dysbiosis. However, formulations and efficacy remain highly variable, highlighting a critical gap in our understanding of the mechanisms that drive successful interventions in this population. Furthermore, current studies on probiotic efficacy rely on indirect or relative measures of intestinal bacterial burden. Here, we directly mapped the biogeography of intestinal colonization and quantified the probiotic effects of\n                      <jats:italic toggle=\"yes\">Escherichia coli<\/jats:italic>\n                      Nissle 1917 (EcN) and\n                      <jats:italic toggle=\"yes\">Ligilactobacillus murinus<\/jats:italic>\n                      strain V10 against\n                      <jats:italic toggle=\"yes\">Klebsiella pneumoniae<\/jats:italic>\n                      dysbiosis across the neonatal murine intestine. Despite substantial differences in their spatial distribution along the intestine, both EcN and\n                      <jats:italic toggle=\"yes\">L. murinus<\/jats:italic>\n                      V10 significantly reduced\n                      <jats:italic toggle=\"yes\">K. pneumoniae<\/jats:italic>\n                      colonization and mortality from\n                      <jats:italic toggle=\"yes\">K. pneumoniae<\/jats:italic>\n                      sepsis, with EcN providing greater protection. EcN\u2019s probiotic activity was partially dependent on high-affinity oxygen respiration, implicating luminal oxygen availability as a key ecological determinant of probiotic efficacy. Contrary to the common assumption that multi-strain probiotics are inherently superior, simultaneous administration of EcN and\n                      <jats:italic toggle=\"yes\">L. murinus<\/jats:italic>\n                      V10 was less effective than EcN treatment alone at preventing sepsis-related death. These findings identify intestinal niche occupancy, oxygen utilization, and strain-strain interactions as critical variables which should inform the rational design of future probiotic interventions for high-risk neonates.\n                    <\/jats:p>\n                    <jats:sec>\n                      <jats:title>IMPORTANCE<\/jats:title>\n                      <jats:p>\n                        Late-onset sepsis (LOS) remains a devastating and difficult-to-treat complication of prematurity, and probiotics are increasingly used to reduce dysbiosis and infection risk in this vulnerable population. Probiotic regimens, however, are highly heterogeneous, and their mechanisms of action in the neonatal intestine are poorly defined, complicating efforts to design safe, effective, and regulatable interventions. In this work, we use a neonatal mouse model of LOS to rigorously test fundamental assumptions underlying the current paradigm for understanding the impact of probiotics on intestinal disease. We demonstrate that two distantly related probiotic bacteria,\n                        <jats:italic toggle=\"yes\">Escherichia coli<\/jats:italic>\n                        Nissle 1917 and\n                        <jats:italic toggle=\"yes\">Ligilactobacillus murinus<\/jats:italic>\n                        V10, each reduce intestinal colonization and mortality caused by the LOS pathobiont\n                        <jats:italic toggle=\"yes\">Klebsiella pneumoniae<\/jats:italic>\n                        , but do so through distinct ecological and molecular mechanisms. These findings highlight ecological principles, including spatial niche occupancy, resource competition, and strain-strain interactions, as critical determinants of probiotic efficacy, and provide mechanistic insight that will be important for guiding rational probiotic strategies for high-risk neonates.\n                      <\/jats:p>\n                    <\/jats:sec>\n                  <\/jats:sec>","DOI":"10.1128\/mbio.01127-26","type":"journal-article","created":{"date-parts":[[2026,8,10]],"date-time":"2026-08-10T13:00:51Z","timestamp":1786366851000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Ecology of protection: probiotic biogeography and sepsis prevention in the neonatal intestine"],"prefix":"10.1128","volume":"17","author":[{"given":"Sierra 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