产ESBLs大肠埃希菌CTX—M型耐药基因分析

目的了解某院CTX-M型超广谱β-内酰胺酶（ESBLs）在大肠埃希菌中的检出率，并确定其基因型。方法对该院2005年1—12月临床送检标本中分离的197株大肠埃希菌进行ESBLs表型确证试验和接合试验；采用聚合酶链反应（PCR）检测CTX-M酶基因型，对PCR产物测序并确定其基因型。结果197株大肠埃希菌中有104株（52．79％）ESBLs表型检测阳性，其中91株符合供体菌标准，64株（70．33％）接合成功，接合子均确证产ESBLS。PCR扩增结果示104株产ESBLs大肠埃希菌中共有98株（94．23％）携带CTX-M型基因，其中38株（36．54％）检出blaCTX-M-1组基因，69株（66．35％）检出blaCTX-M-9组基因。64株接合子中共有51株（79．69％）携带CTX-M型基因，其中18株（28．13％）检出blaCTX-M-1组基因，35株（54．69％）检出blaCTX-M-9组基因。基因测序确定存在CTX-M-22、CTX-M-28、CTX-M-15、CTX-M-14、CTX-M-27五种基因亚型，以CTX-M-14为主。结论该院大肠埃希菌产ESBLs和耐药质粒水平传播情况严重，产ESBLs细菌基因型以CTX-M-9组的CTX-M-14亚型为主，同时存在CTX-M-22、CTX-M-28、CTX-M-15和CTX-M-27等多种亚型。

Analysis on drug-resistant gene of CTX-M extended-spectrum β-lactamase-producing Escherichia coli

Objective To study the detection rates and genotype distribution of CTX-M extended spectrum β-lactamases （ESBLs） in ESBLs-producing Escherichia coli （E. coli） clinical isolates from a hospital. Methods On hundred and ninety-seven ESBLs-producing E. coli isolated between January and December in 2005 were performed confirmation test and conjugation test to determine the horizontal transmission of ESBLs, and the ESBLs genes were detected by polyrnerase chain reaction （PCR）, the genotypes of β-lactamases were confirmed by sequencing of the PCR products. Results Among 197 strains, 104 （52. 79%） E. coli isolates produced ESBLs, 91 of 104 ESBLs-producing E. coli were tested by conjugation, 64 （70. 33 %） transconjugants were acquired. All transconjugants were confirmed to produce ESBLs. 98 strains（94. 23%） carried the genes of CTX-M, 38 strains（36. 54%） of which were the blaCTX-M-1 group, and 69 strains（66. 35%） were the blaCTX-M-9 group. 51 transconjugants （79.69%） carried the genes of CTX-M, 18 strains（28. 13%） of which were the blaCTX-M-1 group, and 35 strains（54. 69%） were the blaCTX-M-9 group. Five CTX-M genotypes were confirmed by sequencing of the PCR products. They were CTX-M-22, CTX-M-28, CTX-M-15, CTX-M-14, CTX-M-27, and CTX-M-14 was the main genotype. Conclusion The prevalence of ESBLs in this hospital is high and the horizontal transmission of ESBLs is serious among the clinical E. coli isolates. The CTX-M-14 is the dominant epidemic type in this hospital, and CTX-M-22, CTX-M- 28, CTX-M-15 and CTX-M-27 also exist.