Aims: The object of the present study was to evaluate the oral toxicity of the recently isolated probiotic bacteria Lactobacillus coryniformis CECT5711 and Lactobacillus gasseri CECT5714.
Methods and results: Enzymatic activity and antibiotic resistance profile were evaluated in vitro. Then, the oral toxicity was analysed by an in vivo experiment using 20 Balb/C mice, which were orally treated with CECT5711 or CECT5714 (10(10) CFU mouse(-1) day(-1)) during 30 days. Results showed that CECT5711 and CECT5714 have no deleterious enzymatic activities and present intrinsic antibiotic resistance profile. Administration of both strains to mice had no adverse effects on body weight or food intake. No bacteraemia was present in liver or spleen and there was no treatment-associated bacterial translocation to these tissues. Liver glutathione content as well as plasma malondialdehide concentration were not statistically different in probiotic-treated mice when compared with control mice. Probiotic treatment did not cause changes in the biochemical and haematological parameters analysed.
Conclusions: These results suggest that strains CECT5711 and CECT5714 are nonpathogenic and likely to be safe for human consumption.
Significance and impact of the study: This study reveals the oral safety of two new lactobacilli strains that are aimed to be used as probiotics in food and pharmaceutical applications.