antibiotic eradication coupled with a chemically defined diet in INS-GAS mice triggers dysbiosis and vitamin K deficiency resulting in gastric hemorrhage.

Infection with causes chronic inflammation and is a risk factor for gastric cancer. Antibiotic treatment or increased dietary folate prevents gastric carcinogenesis in male INS-GAS mice. To determine potential synergistic effects, -infected male INS-GAS mice were fed an amino acid defined (AAD) diet with increased folate and were treated with antibiotics after 18 weeks of infection. Antibiotic therapy decreased gastric pathology, but dietary folate had no effect. However, the combination of antibiotics and the AAD diet induced anemia, gastric hemorrhage, and mortality. Clinical presentation suggested hypovitaminosis K potentially caused by dietary deficiency and dysbiosis. Based on current dietary guidelines, the AAD diet was deficient in vitamin K. Phylloquinone administered subcutaneously and via a reformulated diet led to clinical improvement with no subsequent mortalities and increased hepatic vitamin K levels. We characterized the microbiome and menaquinone profiles of antibiotic-treated and antibiotic-free mice. Antibiotic treatment decreased the abundance of menaquinone producers within orders and . PICRUSt predicted decreases in canonical menaquinone biosynthesis genes, and . Reduction of from , and were confirmed in antibiotic-treated mice. The fecal menaquinone profile of antibiotic-treated mice had reduced MK5 and MK6 and increased MK7 and MK11 compared to antibiotic-free mice. Loss of menaquinone-producing microbes due to antibiotics altered the enteric production of vitamin K. This study highlights the role of diet and the microbiome in maintaining vitamin K homeostasis.