Study of interactions between Listeria monocytogenes and experimental tumors.

Objective: to verify the effects of Listeria monocytogenes (LM) inoculation in the survival of animals bearing Ehrlich's tumor. KIND OF STUDY: experimental. Animals-isogenic mice, Balb/c, female, 19-21 g. Tumor-Ascitic Ehrlich's tumor, dilution of 5 x 10(5) cells/0.1 ml. Bacteria-LM serotype 4a, solution with 7 x 10(3) bacteria (standard sub-lethal dose). Intervention-a) inoculation of LM in mice bearing Ehrlich tumor at the same time as ascitic cells transplantation. b) inoculation of LM seven days before and, again, seven and fourteen days after ascitic cells transplantation. c) to study the effect of using ampicillin 100 mg/kg, im, simultaneously with the inoculation of Ehrlich tumor and LM organisms and, again, 3, 5, 7, 14, 21 and 30 days after the ascitic cells transplantation.

Analysis: Chi-square test; p < 0.05

Results and conclusion: LM increases significantly the survival of mice bearing Ehrlich tumor even when only one inoculum of viable LM was used, seven days before or seven days after the ascitic cells transplantation. The use of ampicillin after the inoculation of LM and tumor transplantation does not alter the survival of mice.