Effects of ceftazidime, a betalactam antibiotic, on murine haemopoiesis in vitro.

Agranulocytosis has been reported in 5-15% of patients treated with high-dose betalactam antibiotics (BLA). We investigated the toxic effect of ceftazidime (CEF) as a representative of these antibiotics on colony-forming unit-granulocyte/macrophage (CFU-GM), on burst-forming unit-erythroid (BFU-E) colony growth and on myelopoiesis in murine long-term bone marrow culture (mLTBMC). The CEF concentration resulting in a 50% inhibition of growth was 146 micrograms/ml (267 microM) for CFU-GM, 132 micrograms/ml (241 microM) for BFU-E and 180 micrograms/ml (329 microM) for myeloid cell production in the supernatant of mLTBMC. Following addition of CEF to mLTBMC, CFU-GM remained low for 1 week and total myeloid cell production remained low for 2 weeks after removal of CEF from culture. Thereafter the values returned to control levels. The myeloid differential counts in the supernatant and adherent layers demonstrated a 'maturation arrest', which could be overcome by simultaneously adding all-trans retinoic acid to culture. These results demonstrate that CEF has reversible inhibitory effects on myelopoiesis and highlight the utility of in vitro haemopoietic assays as models to examine drug-induced haemopoietic dyscrasias.