Effect of feeding lactic acid bacteria and fermented milk on specific and nonspecific immune responses of mice infected with Klebsiella pneumoniae AD-1

The diets of six groups of weaned mice were supplemented with ultra high temperature (UHT) milk containing a washed suspension of lactic acid bacteria (mixture of 8 strains) or with UHT milk fermented by the same strains and heat-treated or not. Control groups received physiological saline or UHT milk only. The mice were infected intranasally by Klebsiella pneumoniae AD-1 on the 13th d of feeding. The effect on the immune system (specific and nonspecific) before and after infection was evaluated by measuring the phagocytosis of alveolar macrophages (using zymosan particles) and by measuring of total immunoglobulin G and A levels in serum and in pulmonary fluid (using the enzyme-linked immunosorbent assay method). Postinfection survival was 0.7 d longer for mice receiving fermented milk than for the saline control group. The percent phagocytosis did not vary significantly, while serum immunoglobulin G levels differed between mice fed fermented milk and those fed bacterial suspensions in unfermented milk. Fermentation appears to be essential for the beneficial effects on the immune system and survival time; this effect no longer occurs after pasteurization of fermented milk