Effect of antibiotics on colony formation from mouse granulocyte-macrophage progenitors (CFU-GM), megakaryocyte progenitors (CFU-M) and erythrocyte progenitors (CFU-E, BFU-E) in vitro.

Mouse bone marrow cells were cultured in vitro in semisolid medium containing various concentrations of beta-lactam antibiotics, moxalactam (LMOX), cefotetan (CTT), flomoxef (FMOX), ceftizoxime (CTZ), cefmenoxime (CMX), cefotasime (CTX), cefamandole (CMD), cefotiam (CTM), carbenicillin (CBPC) or sulbenicillin (SBPC). All of these antibiotics dose-dependently suppressed colony formation from granulocyte or macrophage progenitors (CFU-GM) and from megakaryocyte progenitors (CFU-M). The suppressive potencies of these antibiotics for both progenitors, as evaluated from the drug concentrations that induced 50% suppression of colony formation (IC50), were ranked as the weakest for CBPC and SBPC, moderate for LMOX, CTT, CMX, FMOX and CTZ, and strongest for CMD, CTX and CTM. LMOX, FMOX, CTX, CBPC and SBPC also showed dose-dependent inhibition of colony formation from erythroid progenitors (CFU-E and BFU-E). In the ranking of suppression of colony formation from CFU-E, CMD and CTX showed comparatively strong inhibition but others showed a weak effect, and in that from BFU-E, the effect was weakest for CBPC and SBPC, moderate for LMOX and FMOX, and strongest for CMD and CTX. The suppressive effect of LMOX and CMD on colony formation from each progenitor could almost be prevented by washing the cells after incubation with these antibiotics for 24 hr.