Abstract: Antigenotoxic activity against 4-nitroquinoline-1-oxide (4-NQO)of Bfidobacterium and Lactobacillus isolated from faecal sample of elderly people was studied using the shortterm bacterial assay SOS-chromotest, with Escherichia coli PQ37(sfiA:: lacZ) as the tester organism. It was found that the genotoxicity of 0.1 mmol/L 4-NQO was reduced after coincubation with probiotics (108～109 CFU/ml). All isolates showed potential for deactivating of 4-NQO, and the inhibitory ability was strain specific. Lactobacillus salivarius 24DB 2JC, BCHONG, Bifidobacterium animalis subsp. lactis BBMN BBMN1 and BBMN2 has the higher antigenotoxic ability as 92.91%, 88.55%,89.81%, 80.86% and 83.54% respectively. The possible mechanism was discussed primely.

Key words: Bifidobacterium longum, Lactobacillus salivarius, 4-NQO, genotoxic, SOS-chromotest