天津地区志贺菌属产超广谱β内酰胺酶及其基因型的检测

Study on extended-spectrum β-iactamases and their genotypes of Shigella isolated from Tianjin

目的了解天津地区志贺菌属产超广谱8内酰胺酶（ESBL）的流行基因型、耐药特征和流行病学特征，探讨产ESBL志贺菌属特性与耐药质粒的关系。方法136株志贺菌来源于2009年5月至2010年9月在天津市儿童医院、天津医科大学第二医院及天津市第一中心医院门诊就诊的以脓血便为主的腹泻患者粪便标本，纸片扩散法筛选可疑产ESBL志贺菌属；对产ESBL志贺菌进行接合试验，供体菌和接合子进行耐药性测定，以确定耐药性质粒传递；采用TEM、SHV、CTX—M一1组、CTX—M一2组、CTX-M一9组p内酰胺酶通用引物对产ESBL菌株的基因型进行PCR检测。使用肠杆菌科基因间的重复序列PCR（ERIC-PCR）分析产ESBL菌株的分子同源性。采用X。检验。结果136株志贺菌属中，产ESBL志贺菌20株，检出率为14．7％，未检测出产AmpC酶菌株。其中16株志贺菌基因型为CTX—M-14型，4株为CTX—M-15型；产CTX-M型ESBL菌株对多种抗菌药物耐药，但对亚胺培南的敏感率为100％。18株产ESBL志贺菌接合试验获得成功，其接合子对B内酰胺类抗菌药物耐药。结论天津地区志贺菌属产ESBL基因型以CTX—M型为主，产ESBL是志贺菌属对口内酰胺类耐药的主要原因，产ESBL菌株的传播机制以质粒介导为主。

Objective To study genotypes, antibiotic resistance and epidemiology of extendei- spectrum β-lactamases （ESBL）-producing Shigella isolated in Tianjin, and to discuss the reiationship between ESBL：producing Shigella and drug-resistance plasmid. Methods A total of 136 Shigeiia spp. were isolated from stool specimens of patients with diarrhea who presented mainly with bloodypurulent stool from Tianjin Children＇s Hospital, Tianjin Medical University No. 2 Hospital and TianJin No. 1 Central Hospital between May 2009 and September 2010. Suspicious ESBL-producing isolates were screened by K-B disc diffusion method. The conjugation experiment was performed in theconfirmed ESBL-producing strains and antibiotic resistance was compared between clinical strains and transconjugants to confirm the plasmid-mediated resistance. The genotypes of these isolates were detected by polymerase chain reaction （PCR） using universal primers for TEM, SHV, CTX-M-1group,CTX-M-2 group, CTX-M-9 group, respectively. Intergenic consensus PCR （ERIC-PCR） was employed to understand the molecular homology of the ESBL-producing isolates. The data were analyzed by X2 test. Results ESBL were identified in 14.7% （20/136） of Shigella isolates, but no AmpC enzyme were detected. Among all the Shigella isolates, 16 strains were genotype CTX-M-14, 4 were genotype CTX-M-15. The strains with CTX-M ESBL were resistant to multiple antibiotics,while 100 % sensitive to imipenem. The transconjugant test of 18 ESBL-producing isolates were positive, and these conjugations were only resistant to β-;lactamases. Conclusions CTX-M type is the common genotype of ESBL-producing Shigella isolates in Tianjin. ESBL-producing is the main cause of multiple resistance to β-lactams. The transmission of CTX-M producing strains is mainly mediated by plasmids.