Bacterial decontamination and antileukemic therapy of AKR mice.

Four nonabsorbable antibiotics (streptomycin, neomycin, bacitracin, and amphotericin B) and a germicidal dip solution (Zephiran chloride/water) were used to eliminate all the detectable bacteria from conventional AKR mice. Control mice were not decontaminated and were used as such. When antibiotic-decontaminated and control mice developed clinical manifestations of spontaneous lymphatic leukemia, each was treated for the disease with an antitumor drug (cyclophosphamide [CP]) at weekly intervals. With the decontamination procedure, mice of each of the two groups became bacteria-free after 16 weeks of continuous oral administration of the antibiotics and two separate germicidal dippings. All decontaminated mice remained free of bacteria throughout the experiment. The bacterial flora of the control mice remained unaltered. With CP therapy, the mean survival time of the female decontaminated mice was 65 days, whereas that of male mice was 218 days. The average survival time of the CP-treated control leukemic mice was 51 days. Untreated decontaminated or control mice usually died of leukemia within 7 days after the onset of symptoms of leukemia. Although CP therapy was not curative, it did prolong the life expectancy of the decontaminated mice significantly.