Umbilical-cord hematopoietic stem-cell transplantation.
Cord colitis "a syndrome of colitis that appears to be unique to patients undergoing umbilical-cord HSCT has been described. The syndrome termed “cord colitis” is clinically and histopathologically distinct from other known causes of colitis in patients undergoing HSCT. This syndrome of non- bloody, frequent stools developed 3 to 11 months after umbilical-cord HSCT in 11 of 104 patients (11%) at a single center. Histopathological evaluation of colon-biopsy samples revealed chronic active colitis and epithelioid granulomas, without evidence of known microbial pathogens, viral cytopathic changes, or signs of GVHD (PubMed)" (PubMed).
"Organisms related to B. enterica have shown direct or inferred sensitivity to fluoroquinolones and metronidazole, the therapy that was effective in the treatment of patients with cord colitis in the original cohort."
It may also have been a contaminant. Cord colitis appears to be more than GVHD and is antibiotic responsive (PubMed).