Impact of probiotic supplementation on mortality of induced 1,2-dimethylhydrazine carcinogenesis in a mouse model.

Rationale: Probiotic bacterial strains have been increasingly used in clinical practice as many health benefits result from their use. However, severe side effects such as bacteremia and fungemia have been reported in inmunocompromised patients and those with chronic disease.

Objective: The purpose of this study was to report the impact of probiotic supplementation on the mortality of mice undergoing carcinogenesis induction with 1,2-dimethylhydrazine (DMH).

Methods: Two treatment protocols were used. In experiment 1, Lactobacillus delbrueckii UFV-H2b20, Bifidobacterium animalis var. lactis Bb12, and Saccharomyces boulardii were added to the drinking water, to control mice and those undergoing injections of DMH daily. Probiotic supplementation was started 1 wk before and continued throughout the 6 wk of DMH injections. In experiment 2, the same probiotics were administered daily, except on the first day that DMH was administered. The mortality of these animals was recorded. Bacterial translocation was determined in mice in experiment 1.

Results: Groups with DMH-induced injury treated with lactobacilli, bifidobacteria, and the mixture of lactobacilli and bifidobacteria presented with 40%, 30%, and 60% mortality, respectively. Death happened mainly between 48 h and 72 h after the first injection of DMH. On the other hand, no mice in experiment 2 died during the study period. Bacteria were found to be translocated to mesenteric lymph nodes, spleen, and liver.

Conclusion: Supplementation of L. delbrueckii UFV-H2b20 and B. animalis var. lactis Bb12 in mice with DMH-induced injury led to death in some animals. The results suggest that increased bacterial translocation was probably related to mortality. These findings are an alert to the potentially severe side effects associated with the use of probiotics under extremely stressful situations.