CR-hvKP的出现对公众健康构成重大威胁。项目组前期研究发现，fecA2基因在KL64-CR-hvkp中的阳性率高达72%，KL47-CR-hvkp中没有该基因，且前者毒力显著高于后者。我们利用CRISPR基因编辑技术敲除了KL64-CR-hvKP的fecA2基因，与野生株相比感染大蜡螟后生存率明显增加。RT-PCR结果发现在低铁的条件下，高表达fur基因后KL64-CR-hvkp的fecA2表达量显著高于野生株。我们推测，fecA2可能受fur基因调控增强KL64-CR-hvkp的毒力。本项目拟通过构建fecA2阴性回复突变株，利用一系列的试验研究FecA2在KL64型高毒力高耐药肺炎克雷伯菌中的致病性、铁摄取能力、免疫逃避及fecA2基因表达调控机制。探明FecA2在KL64-CR-hvkp在致病中的作用，为开发针对CR-hvKP临床药物提供潜在靶标。

CR-hvKP isolates pose a significant threat to the public health. In the previous study, the virulence of KL47 CR-hvKP isolates was significantly lower than KL64 CR-hvKP isolates. And 72% of the KL64 CR-hvKP isolates were found to carry fecA2 but not found in all KL47 CR-hvKP isolates. We suspected that FecA2 was shown to be crucial in CR-hvKP isolates pathogenicity. fecA2 has been knocked out in KL64-CR-hvKP, named KL64 ΔfecA2. Compared with wild type strain, the survival rate of greater wax moth infected by KL64 ΔfecA2 increased significantly. RT-PCR results showed that under low iron conditions, the expression of fecA2 in KL64-CR-hvkp was significantly higher than that of wild strains after high expression of the fur gene. We speculated that fecA2 may be regulated by the fur gene to enhance KL64 type high virulence and high tolerance The virulence of the drug Klebsiella pneumoniae. To corroborate our speculation, we will construct complementary strain of KL64 ΔfecA2. with plasmid containing fecA2 and further investigate the role of FecA2 in pathogenicity of KL64 CR-hvKP isolates. The aim was to clarify the role of FecA2 in pathogenicity, iron uptake, immune evasion of KL64 CR-hvKP. The mechanism of fecA2 expression will be further studied. These integrated data can help lead a pathogenicity investigation in CR-hvKP and provide the basis for downstream diagnostic and novel drugs that are key virulence factors for CR-hvKP discovery studies.