Gastrointestinal Administration National Center for Biotechnology Information NCBI NLM MEDLINE humans pubmed abstract nih national institutes of health national library of medicine research support non-u.s. gov't female male aged middle aged Recurrence Randomized Controlled Trial Feces / microbiology* diarrhea / drug therapy diarrhea / microbiology combined modality therapy anti-bacterial agents / therapeutic use* oral intubation diarrhea / therapy* clostridium difficile* vancomycin / therapeutic use* pmid:23323867 doi:10.1056/nejmoa1205037 els van nood anne vrieze josbert j keller duodenum metagenome therapeutic irrigation