DNA damage in intact cells induced by bacterial metabolites of chloramphenicol

Four chloramphenicol (CAP) metabolites known to be produced by intestinal bacteria were examined with respect to their capacity to induce DNA damage in intact cells. The induction of DNA single-strand breaks in Raji cells, activated human lymphocytes, and human marrow cells was assayed by the alkaline elution technique. One of the four compounds tested, dehydro-CAP, was capable of inducing DNA single-strand breaks in all three cell systems at concentrations of 10(-4) M. This effect is comparable to that observed previously with nitroso-CAP, the nitroreduction intermediate of CAP. The nitroreduction of dehydro-CAP by human bone marrow cell homogenate was detected by the production of the corresponding amino derivative amounting to 5.6 X 10(-5) M from 2 X 10(-3) M substrate under aerobic conditions. In sharp contrast, nitroreduction of CAP by bone marrow could not be demonstrated. The genotoxicity of dehydro-CAP, its relative stability compared to the nitroso-CAP, and its nitroreducibility by bone marrow suggest that this bacterial metabolite of CAP may play a key role as a mediator of aplastic anemia in the predisposed host.