高毒力鲍曼不动杆菌医院感染的溯源及传播路径分析

Tracing and transmission analysis of a nosocomial infection event caused by hypervirulent Acinetobacter baumannii

目的通过回溯性研究院内的一次高毒力鲍曼不动杆菌感染暴发事件,寻找并鉴定引起此次事件的传染源及传播媒介。方法收集深圳市人民医院2018年7至8月呼吸科普通病房和呼吸重症监护病房分离的9株耐碳青霉烯类鲍曼不动杆菌(Carbapenem-resistantAcinetobacter baumannii,CRAB),并采集病房环境物体表面和医务人员手部等环境标本。用Vitek 2对检出的CRAB进行菌种鉴定和药敏试验,用Illumina HiSeq 2500平台、Staramr、Ridom SeqSphere+进行全基因组测序、耐药基因检测及多位点序列分型,用IQ-Tree软件、BEAST2软件包和SCOTTI软件构建系统进化树和传播路径图。同时利用小鼠肺炎模型检测病原菌的毒力。结果9株CRAB菌株均为ST2型,均携带耐碳青霉烯基因blaOXA-23,荚膜型分别为KL49、KL3、KL77和KL2。1株环境分离(可移动呼吸机屏幕)CRAB菌株为ST2型及KL49型荚膜。系统进化树分析显示环境分离株与其中5株CRAB位于同一分支,传播路径图显示这5株CRAB也位于同一条传播链。5株CRAB涉及4个致死病例,小鼠体内实验验证了引起致死感染的菌株具有高毒力表型。结论高毒力鲍曼不动杆菌可在移动医疗设备表面定植,共享这些设备可能导致医院内病原菌传播。利用新型传播路径分析工具对传播事件的调查有一定的参考意义。

Objective To trace and identify the source and the transmission vector of a nosocomial infection event caused by hypervirulent Acinetobacter baumannii.Methods Nine strains of carbapenem-resistant Acinetobacter baumannii(CRAB)isolated from respiratory general ward and respiratory intensive care unit in Shenzhen People’s Hospital from July to August 2018 were collected.Environmental specimens such as ward environmental objects and medical staff’s hands were also collected.Vitek 2 was used for identification of bacterial species and drug susceptibility testing;Illuinam HiSeq 2500 platform,Staramr,Ridom SeqSphere+were used for whole genome sequencing,drug resistance gene detection and multi-locus sequence typing(MLST);and IQ-Tree software,BEAST2 software package and SCOTTI software were used to construct phylogenetic tree and propagation path map.At the same time,the virulence of pathogenic bacteria was detected by mouse pneumonia model.Results The 9 isolated CRAB strains were all ST2 type,all carried the carbapenem-resistant gene blaOXA-23,and the capsular types were KL49,KL3,KL77 and KL2,respectively.One of the CRAB strains isolated from removable ventilator screen was ST2 type and KL49 type capsule.Phylogenetic tree analysis showed that the environmental isolates were located in the same branch as 5 CRABs,and the transmission path map showed that these 5 CRABs were also located in the same transmission chain.Five strains of CRAB were involved in four lethal cases,and in vivo experiments in mice confirmed that the strains causing lethal infection had a hypervirulent phenotype.Conclusions Highly virulent Acinetobacter baumannii can colonize the surface of mobile medical equipment,and sharing these equipment may lead to nosocomial spread of pathogens.The use of new propagation path analysis tools has certain reference significance for the investigation of propagation events.