Lactic acid bacteria induce apoptosis inhibition in Salmonella typhimuriuminfected macrophages

The immunomodulating effect of lactic acid bacteria (LAB) on the gut associ ated lymphoid tissue (GALT) and the protective capacity of some of them aga inst enteric infections is well documented. The ability of enteroinvasive p athogens to disseminate into the deep tissues by cellular apoptosis inducti on is also demonstrated Peritoneal macrophages from BALB/c mice were used t o performed in vitro apoptosis assays and to determine oxidant radicals pro duction induced by Lactobacillus delbrueckii ssp. bulgaricus and Streptococ cus thermophilus, against an in vitro Salmonella typhimurium. infection. We determined whether or not the LAB assayed induces apoptosis inhibition of macrophages infected with the pathogen. Fluorescent DNA fragmentation assay (Tunel test) was used to investigate the ability of the LAB to inhibit mac rophage's apoptosis. We determined that Lactobacillus and Streptococcus wer e able to inhibit the apoptosis of macrophages induced by Sal. typhimurium, L. delbrueckii ssp. bulgaricus being the more effective one. The results s uggest that these microorganisms could play a role in apoptotic mechanisms, since the inhibition of it would avoid pathogen dissemination. The knowled ge that S. thermophilus and L. delbrueckii ssp. bulgaricus have immunopoten tiation capacity led us to demonstrate that such apoptosis inhibition obser ved might be mediated by other process such as the release of oxidant radic als able to kill the pathogen. The preventive effect of LAB against Sal. ty phimurium infection could be mediated by apoptosis inhibition.