Abstract:

Objective To compare the changes of virulence of Enterobacter cloacae before and after blaNDM-1 gene knockout， and to clarify the effect of blaNDM-1 gene on the virulence of Enterobacter cloacae. Methods The Enterobacter cloacae carrying blaNDM-1 gene were divided into Enterobacter cloacae T2 carrying drug resistant gene blaNDM-1 group（T2 group），Enterobacter cloacae T2 with blaNDM-1 gene-knockout group （ΔT2 group） and Enterobacter cloacae ATCC13047 control group （ST group）. The stabilities of the plasmids in various groups were detected，and the colony movement diameters，biofilm absorbance （A）values， amounts of adhesion bacteria， adhesion rates and invasion adhesion ratios of the Enterobacter cloacae in various groups were detected. Results After 200 passages， the Enterobacter cloacae in T2 group still carried blaNDM-1 gene， while the Enterobacter cloacae in Δ T2 and ATCC13047 groups did not carry blaNDM-1 gene；the Enterobacter cloacae inT2 group only carried the carbapenem resistance gene blaNDM-1， while the other carbapenem resistance genes blaKPC-2， blaIMP-4， blaVIM-1 and blaOXA-48 were negative； five carbapenem resistance genes detected in Δ T2 and ST groups were negative；the Enterobacter cloacae in T2 and Δ T2 groups carried the same virulence genes clpB， icmf and acrA. The colony movement diameter of the bacteria in T2 group was smaller than those in Δ T2 and ST groups （P<0.05）. Compared with T2 group， the biofilm A value in Δ T2 group was increased，but the difference was not significant（P>0.05）. Compared with T2 group， the amount of adhesion bacteria in Δ T2 group was decreased，but the difference was not significant（P>0.05）. After co-culture for 24 h， the adhesion rate and invasion adhesion ratio of the RAW264.7 cells in T2 group and Δ T2 group were lower than that in ST group （P<0.05）. Conclusion BlaNDM-1 does not significantly increase the virulence of Enterobacter cloacae.

Key words: Enterobacter cloacae, BlaNDM-1, Gene knockout, Virulence, Drug-resistance