AIM: To investigate the potential therapeutic effect of exopolysaccharide (EPS)-producing Streptococcus thermophilus ( S. Thermophilus) CRL 1190 fermented milk on chronic gastritis in Balb/c mice.METHODS: Balb/c mice were fed with the fermented milk for 7 d after inducing gastritis with acetyl-salicylic acid (ASA, 400 mg/kg body weight per day for 10 d).Omeprazole was included in this study as a positive therapeutic control. The gastric inflammatory activity was evaluated from gastric histology and inflammation score, number of interleukin-10 (IL-10), interferon-γ (INFγ) and tumor necrosis factor-α (TNF-α) cytokineproducing cells in the gastric mucosa, and thickness of the mucus layer.RESULTS: Animals receiving treatment with the EPSproducing EPSproducing S. Thermophilus CRL 1190 fermented milk showed a conserved gastric mucosa structure similar to that of healthy animals. Inflammation scores of the fermented milk-treated mice were lower than those of mice in the gastritis group (0.2 ± 0.03 vs 2.0 ± 0.6, P < 0.05). A marked decrease in INFγ+ (15 ± 1.0 vs 28 ± 1.2, P < 0.05) and TNF-α+ (16 ± 3.0 vs 33 ± 3.0, P < 0.05) cells and an increase in IL-10+ (28 ± 1.5 vs 14 ± 1.3, P < 0.05) cells compared to the gastritis group, was observed. Also, an increase in the thickness of the mucus gel layer (2.2 ± 0.6 vs 1.0 ± 0.3; 5.1 ± 0.8 vs 1.5 ± 0.4 in the corpus and antrum mucosa, respectively, P < 0.05) compared with the gastritis group was noted. A milk suspension of the purified EPS from S. Thermophilus CRL1190 was also effective as therapy for gastritis.CONCLUSION: This study suggests that fermented milk with S. Thermophilus CRL 1190 and/or its EPS could be used in novel functional foods as an altative natural therapy for chronic gastritis induced by ASA.