blaCTX-M-55介导的宋内志贺菌耐药机制研究  

Resistance mechanisms of bla_(CTX-M-55) in a clinical Shigella sonnei strain

作　　者：蒋晓圆 刘东[3] 徐丽[3] 方海红[2] 冯娇[2] 殷喆[2] 周冬生[1,2] 王丽[3] 张德福[2,4] 宋亚军[1,2] 

机构地区：[1]安徽医科大学,合肥230032 [2]军事医学科学院微生物流行病研究所,病原微生物生物安全国家重点实验室,北京100071 [3]河南大学第一附属医院检验科,河南开封475000 [4]渤海大学食品科学与工程学院,生鲜农产品贮藏加工及安全控制技术国家地方联合工程研究中心,辽宁锦州121013

出　　处：《军事医学》2016年第9期717-721,共5页Military Medical Sciences

基　　金：国家自然科学基金青年资助项目(81501779);安徽省教育厅自然科学基金资助项目(KJ2015A019)

摘　　要：目的研究bla_(CTX-M-55)介导的宋内志贺菌#1083的耐药机制。方法双纸片协同扩散法验证#1083是否为产超广谱β-内酰胺酶(ESBL)菌株;PCR方法鉴定其耐药基因;接合转移实验验证携带ESBL基因的质粒是否具有可转移性;VITEK 2仪器检测菌株对多种抗生素的MIC值;基因组测序鉴定介导耐药基因转移的移动元件;引物延伸实验鉴定耐药基因转录起始位点。结果 #1083为bla_(CTX-M-55)介导产ESBL的菌株,携带bla_(CTX-M-55)的耐药质粒可通过接合转移的方式进入受体菌EC600,并使受体菌具有相应的耐药谱;介导bla_(CTX-M-55)转移的转座单元为ISEcp1-bla_(CTX-M-55)-Δorf477,且其上游的插入序列ISEcp1为耐药基因提供强启动子区,促进耐药基因表达,且此表达为恒定表达,不受抗生素的诱导作用影响。结论质粒携带的bla_(CTX-M-55)为#1083的主要耐药基因,插入序列ISEcp1介导此基因的表达与传播。Objective To characterize the resistance mechanisms of a clinical Shigella sonnei strain harboring blaCTX-M-55 .Methods A double-disk synergy test was conducted to detect ESBL.Antibiotic resistance genes were determined by PCR followed by amplicon sequencing.Conjugation experiments were performed to verify the transferability of the plasmids carrying ESBL genes.The minimum inhibitory concentration values were tested using VITEK 2.The transposition unit was confirmed by DNA sequencer,and the transcriptional start site was identified using primer extension assay.Results Strain #1083 produced CTX-M-55,which was encoded by plasmid p1083-CTXM that could be transferred into E.coli through conjugation experiments to confer corresponding antibiotic resistance to the transconjugant #1083-EC600.The transposition unit mediating the transfer of blaCTX-M-55 was ISEcp1-blaCTX-M-55 -Δorf477.ISEcp1 offered strong promoter regions for the resistance genes,facilitating their expressions.Besides,the expressions were constant,not induced by antibiotics.Conclusion BlaCTX-M-55 on plasmids is the major resistance genes for strain #1083.Their expressions and spread are mediated by the insertion sequence ISEcp1.

关 键 词：宋内志贺菌 blaCTX-M-55 耐药基因 转座单元 表达与传播 

分 类 号：R446.5[医药卫生—诊断学] R440[医药卫生—临床医学]