非产ESBL大肠埃希菌获得bla CTX-M基因前后在小鼠烧伤伤口定植转移能力研究

Study of the colonizing and transferring ability of the non-ESBL Escherichia coli in burn wounds in mice before and after the acquisition of bla CTX-M gene

目的观察水中产超广谱β-内酰胺酶(extended-spectrum-beta lactamase,ESBL)大肠埃希菌(E.coli)在小鼠烧伤伤口转移β-内酰胺酶CTX-M型基因(blaCTX-M),研究非产ESBLE.coli获得blaCTX-M基因前后在小鼠烧伤伤口定植和向脏器转移情况,为涉水作业人员伤口耐药菌感染提供防治依据。方法构建Balb/C小鼠烧伤模型;皮下注射E.coli菌液模拟伤口感染;用选择性培养基筛选实验菌株并进行统计分析;用PCR方法确证菌株耐药基因型及同源性。结果在烧伤模型伤口内,产ESBLE.coli452实验菌可将blaCTX-M基因转移给非产ESBLE.coliNK5449,转移频率为3.0×10^-1;E.coliNK5449和E.coliCON感染组小鼠在感染后1d、4d和7d,其烧伤部位单位质量肌组织菌落数量先增后降;对于E.coliCON感染组,1d、4d和7d后,烧伤处肌组织单位质量菌落比较差异有统计学意义(P<0.01),E.coliCON与E.coliNK5449感染烧伤模型后1d,肠和肝脏内均培养出实验菌,但差异无统计学意义(P>0.05),感染后4d和7d,均未检出实验菌。感染后1d、4d和7d,两个感染组小鼠肺脏均未检出实验菌。结论小鼠烧伤模型伤口混合感染时,菌株间可发生耐药基因转移;获得blaCTX-M耐药基因的受体菌可能具有更强的定植能力;伤口肌组织内的实验菌先增后降并向肠和肝脏转移。

Objective To observe the bla CTX-M gene transfer of the extended spectrum beta lactamase-producing(ESBL-producing)Escherichia Coli(E.coli)in mouse burn wound model,and to evaluate and compare the ability of colonization and transfer of non-ESBL Escherichia coli in burn wounds before and after the acquisition of bla CTX-M gene to provide a basis for the prevention and control of wound infection in water related working environment.Methods Balb/C mice were used to construct the burn model.E.Coli liquid was injected subcutaneously to simulate wound infection.The experimental bacteria strains were screened by selective culture medium and statistical analysis was carried out.Genotypes of drug-resistant strains and homology of related strains were confirmed by PCR.Results In the burn wound model,ESBL-producing E.coli 452 was able to transfer the bla CTX-M gene to E.Coli NK5449,and the average transfer frequency was 3.0x10^-1.In E.Coli NK5449 and E.Coli CON infected mice,it was found that the number of colonies per unit mass of muscle tissue increased first and then dropped at 1 d,4 d and 7 d after infection.For E.Coli CON infection group,there was a statistically significant difference in the number of bacteria colonies in the muscle tissue of burn at 1d,4d and 7d(P<0.01).E.Coli CON and E.Coli NK5449 were detected in the intestinal and liver tissues of the burn model after 1d,and there was no statistically significant difference between the two groups.No infected bacteria were detected in the intestinal and liver tissues at 4d and 7d.At 1d,4d and 7d,no infected bacteria were detected in the lung tissues of the mice in the two infection groups.Conclusion Horizontal transfer of bla CTX-M genes can occur in burn model wound with mixed infection.The recipient bacteria obtaining bla CTX-M gene may have stronger colonization ability.The number of bacteria in wound muscle tissue presented a trend of increasing first and then decreasing,and then transferred to the intestine and liver.