湖南地区CTX-M型超广谱β内酰胺酶的研究

Study on CTX-M-type extended-spectrum-β lactamase in Hunan province

目的了解湖南本地区产CTX-M型超广谱β内酰胺酶(ESBLs)肠杆菌科细菌的检出率,确定其基因型,并对其流行病学特征进行研究。方法收集2004年10月至2005年7月湖南地区中南大学3家附属医院临床标本分离的多重耐药肠杆菌科细菌171株,按临床实验室标准委员会(CLSI/NCCLS)所推荐的方法进行表型确证试验,聚合酶链反应(PCR)进一步进行CTX-M酶基因型的检测,PCR产物测序并确定其基因型。结果171株多重耐药革兰阴性杆菌中142株表型检测阳性,经多重PCR扩增109株携带CTX-M基因,其中大肠埃希菌45株,肺炎克雷伯菌29株,阴沟肠杆菌21株,其他菌株14,CTX-M酶在产ESBLs肠杆菌科细菌中检出率达76·8%(109/142),经测序25株共检出3种基因型,即7株携带CTX-M-15、7株携带CTX-M-3和11株携带CTX-M-14。RAPD共做50株菌,26株大肠埃希菌有12种RAPD类型,14株肺炎克雷伯菌有6种RAPD类型,10株阴沟肠杆菌有7种RAPD类型。结论在湖南地区检出3种CTX-M型ESBLs基因,在一定程度上CTX-M酶存在克隆传播。

Objective To investigate the prevalence of CTX-M-producing Enterobacteriaceae isolates in the region. To identify the subtype of CTX-M encoding gene and study the epidemiological aspect of CTX-M-producing isolates. Methods 171 clinical strains of multi-resistant Enterobacteriaceae isolates were collected from three affiliated hospitals of Central South University in Hunan province from October 2004 to July 2005. ESBLs producing isolates were confirmed by means of phenotypic confirmatory tests as recommended by the CLSI/NCCLS. PCR and DNA sequencing were used to determine the genotype of the CTX-M enzymes. The homology of CTX-M-producing strains were detected by RAPD （ Random Amplified Polymorphic DNA ） typing method. Results 109 of 142 ESBL-producing Enterobacteriaceae isolates were confirmed to produce blaCTX-M genes by multiplex PCR, they are 45 E. coli , 29 K. pneumoniae, 21 E. cloacae and the other 14, the rate of ESBLs-producing strains carring CTX-M-type β-lactamases in Enterobacteriaceae was 76. 8% . The subtypes of CTX-M enzymes were CTX-M-15 and CTX-M-14, and CTX-M-3. There were 12 RAPD types in 26 isolates of CTX-M-producing E. coli, 6 types in 14 isolates of CTX-M-producing K. pneumoniae, 7 types in 10 isolates of CTX-M-producing E. cloacae. Conclusions CTX- M-producing Enterobacteriaceae were common in Hunan province. To some extent, clone spread has played a certain role in dissemination of CTX-M enzymes.