SUPPRESSION OF PROGENITOR-CELL GROWTH BY VANCOMYCIN FOLLOWING AUTOLOGOUS STEM-CELL TRANSPLANTATION

The occurrence of hematologic side-effects resulting from the use of v ancomycin is rare. Prior to this report, vancomycin-induced neutropeni a was believed to be due to a hypersensitivity reaction since antibodi es directed against circulating neutrophils have been discovered in th e serum of some patients, We demonstrate suppression of hematopoietic bone marrow progenitor cells in a patient experiencing vancomycin-indu ced neutropenia after an autologous hematopoietic stem cell transplant ation for multiple myeloma. A bone marrow (BM) specimen obtained at th e time of neutropenia demonstrated direct suppression of progenitor ce ll growth in vitro when vancomycin was added at increasing concentrati ons (1, 10 and 50 mu g/ml). No such trend was noted in a BM sample fro m the same patient obtained 11 months prior to transplantation and a n ormal control BM. The decrease in the total number of colony-forming u nits (CFU) was statistically significant at all the dose levels of van comycin when compared to the number of CFU in the baseline BM sample ( P <0.05). The myeloid maturation arrest observed in the bone marrow sa mple obtained during the period of neutropenia and the dose dependent growth inhibition by vancomycin observed in vitro suggest a novel noni mmune mechanism of hematologic effects due to suppression of bone marr ow progenitor cell growth.