Lactobacillus in Preventing Infection in Patients Undergoing a Donor Stem Cell Transplant for Hematologic Cancer or Myelodysplastic Syndrome

DISEASE CHARACTERISTICS: * Currently undergoing allogeneic stem cell transplantation from a related or unrelated donor for a hematologic malignancy or myelodysplastic syndrome * Hematopoietic engraftment as evidenced by recovery of the absolute neutrophil count \> 1000/μL for \> 3 days without filgrastim (G-CSF) support within 30 days of transplant PATIENT CHARACTERISTICS: * ECOG performance status 0-2 * Serum creatinine ≤ 2.0 * AST or ALT ≤ 3 times upper limit of normal (ULN) * Total bilirubin ≤ 2.0 times ULN * No clostridium difficile enterocolitis diagnosed during the transplant hospitalization in the peri-transplant period * Able to take medications by mouth * No evidence of graft-vs-host disease * No history of inflammatory bowel disease or other chronic diarrheal illness * No history of hypersensitivity to milk proteins PRIOR CONCURRENT THERAPY: * See Disease Characteristics * More than 3 months since prior use of probiotics supplements, excluding yogurt and cheeses with live cultures * No concurrent over-the-counter medications or herbal remedies