Abstract: Listeria monocytogenes (LM) is a food-borne pathogenic bacterium, which can penetrate multiple host barriers.
Its virulence factors among the internalin protein family are deemed to play an important role in the penetration of the host
barrier by LM. In the present study, homologous recombination method was used to knock out both the inlA and inlB genes
in the wild-type strain EGDe, Realtime-PCR was applied to monitor the expression of the main LM virulence genes and to
explore the effects of gene mutations on the invasion of LM to HT29 colon cancer cells. The results showed that LM growth
was not affected by genetic mutation, but the expression of many virulence genes was changed, and the invasion ability
of the mutant strains to HT29 colon cancer cells decreased significantly (P < 0.05). The deletion mutation strains were
constructed successfully to explore the effect of deletion mutations on LM invasion to host cells. This study can provide
support for further studies to understand the specific roles of InlA and InlB in the process of LM invasion to host cells.

Key words: Listeria monoeytogenes, internalins, gene knock-out, Realtime-PCR, host cell invasion