MODULATION OF THE INTESTINAL MICROFLORA BY THE NONABSORBABLE ANTIBIOTIC VANCOMYCIN LEADS TO A REDUCTION OF THE TUMOR LOAD IN LIVER AND SPLEEN IN A LEUKEMIC RAT MODEL

Based on previous studies where it was shown that non-absorbable antib iotics can influence the normal hematopoiesis via changes in factors r elated to the intestinal microflora, the influence of vancomycin on th e progression of acute myeloid leukemia was investigated in the BNML r at model. Oral vancomycin, which selectively reduces Gram-positive bac teria in the gut, leads to diminution of the leukemic load in liver an d spleen by 30-60%. This 'antileukemic effect' is not dependent on Gra m-negative bacteria as source for endotoxin. The presumed mechanism is a decrease of the leukemic growth fraction caused by alterations in t he absorption of substances from intestinal Gram-positive bacteria.