Am J Gastroenterol. 1994 Jun;89(6):915-23. The contribution of vitamin K2 (menaquinones) produced by the intestinal microflora to human nutritional requirements for vitamin K. Conly JM, Stein K, Worobetz L, Rutledge-Harding S. BACKGROUND: Coagulopathy manifest by elevation of the prothrombin time (PT) in patients receiving broad spectrum antimicrobials indirectly suggests a role for intestinal microflora synthesized [...]