PRIOR CONCURRENT THERAPY: Biologic therapy: At least 6 months since any prior bone marrow transplantation At least 4 weeks since prior biologic therapy and recovered No other concurrent biologic therapy No prior allogeneic transplants Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas and mitomycin) and recovered No concurrent chemotherapy Endocrine therapy: At least 2 weeks since prior hormonal therapy No concurrent steroids Radiotherapy: At least 4 weeks since prior radiotherapy and recovered No concurrent radiotherapy Surgery: See Disease Characteristics At least 2 weeks since prior surgery and recovered No artificial implant (e.g., heart valves or prosthetic hips or knees) No prior splenectomy Other: No other concurrent antibiotics No concurrent immunosuppressives No concurrent medications that directly or indirectly suppress the immune system