Abstract: To study the influence of rmlD deletion on phenotype and virulence of Salmonella typhimurium, S. typhimurium ΔrmlD mutant of S100 ΔrmlD was constructed by suicide plasmid-mediated homologous recombination. The biological characteristics of the ΔrmlD mutant showed that no difference was observed for the growth curve, sensitivity to polymyxin B and DOC of rmlD strain and the wild-type strain S100. However, the ability of adhesion and invasion was significantly increased compared to that of the wild-type strain. In addition, the rmlD mutant strain showed approximately 2000-fold decrease in virulence. In conclusion, deletion of rmlD gene had no effect on the growth and the sensitivity to polymyxin B or DOC, but significantly decreased the virulence. These data indicated that rmlD gene deletion could be an efficient way to reduce the virulence of Salmonella typhimurium for vaccine development. 

Key words: S.typhimurium, rmlD gene, deletion mutant, virulence