耐碳青霉烯鼠伤寒沙门菌的药敏及分子特征分析

The resistance pattern and molecular characteristics of carbapenem resistant Salmonella typhimurium

目的分析鼠伤寒沙门菌的耐药情况及分子特征,为临床治疗和感染防控提供依据。方法对我院分离的鼠伤寒沙门菌CYEY-S001,采用VITEK2-Compact全自动微生物分析系统和K-B纸片法对药敏结果进行检测。通过全基因组测序分析其基因和分子特征,并进行质粒接合试验,研究质粒的可转移性。利用碳青霉烯酶表型试验检测其实所含的碳青霉烯酶类型,PCR确认其携带的耐药基因,质粒复制子分型确定质粒类型。结果该鼠伤寒沙门菌CYEY-S001对除氨曲南之外的青霉素类、头孢菌素类和碳青霉烯类抗生素全部耐药,全基因组测序分析表明其为ST34型鼠伤寒沙门菌,含有bla_(NDM-5)、aac(6’)-Iaa、floR、cmlA1、sul3和tet(A)等多种耐药基因。携带的质粒类型为IncHI2,bla_(NDM-5)位于该质粒上,可通过水平转移,结合子获得了与鼠伤寒沙门菌完全一致的耐药结果。3种碳青霉烯酶表型试验均正确识别出了其携带碳青霉烯酶的类型为金属β-内酰胺酶。结论碳青霉烯耐药鼠伤寒沙门菌对感染治疗和预防控制带来了新的挑战。新发现的IncHI2-bla_(NDM-5)质粒存在向其他细菌物种横向传播的风险。

Objective To analyze the resistance pattern and molecular characteristics of carbapenem resistant Salmonella typhimurium,and provide evidence for clinical treatment and infection prevention and control.Methods The antibiotic susceptibility testing of carbapenem resistant Salmonella typhimurium CYEY-S001 isolated from our hospital was performed by VITEK2-Compact automatic bacterial analysis system and the K-B disk method.The gene and molecular characteristics were analyzed by whole genome sequencing(WGS),and the conjugation test was carried out to study the transferability of the plasmid.Carbapenemase phenotypic assays were used to detect the carbapenemase type.PCR was used to confirm the resistance genes,and plasmid replicon typing was used to determine the plasmid type.Results The Salmonella typhimurium CYEY-S001 was resistant to penicillins,cephalosporins and carbapenems except for aztreonam.The WGS analysis showed that the Salmonella typhimurium CYEY-S001 belonged to the ST34 type,which contained bla_(NDM-5),aac(6’)-Iaa,floR,cmlA1,sul3 and tet(A)resistance genes. The Salmonella typhimurium CYEY-S001 contained IncHI2 plasmid, on which bla_(NDM-5) was located. The antibiotic susceptibility results of the transconjugant were completely consistent with the Salmonella typhimurium CYEY-S001. The three phenotypic tests correctly identified the type of carbapenemase as metal β-lactamase. Conclusion Carbapenem resistant Salmonella typhimurium presents new challenges for infection treatment, prevention and control. The newly IncHI2-bla_(NDM-5) plasmid has the risk of horizontal transmission to other bacterial species.