超广谱β-内酰胺酶CTX-M-3和SHV-12在临床分离阴沟肠杆菌中的流行

目的：了解临床分离的阴沟肠杆菌中产ESBLs菌株的发生率，流行特征以及ESBLs的表型和基因型。方法：1999年2月至2001年3月期间解放军总医院临床临床分离到106株阴沟肠杆菌，研究对象为其中对第三代头孢菌素或氨曲南敏感性减低的42株阴沟肠杆菌，通过等电聚焦电泳和接合试验分析ESBLs的表型特征；PCR扩增TEM型、SHV型和CTX－M型β－内酰胺酶的编码基因并对其进行DNA测序，以确定ESBLs的基因型，有杉ERIC－PCR分型方法分析我院产ESBLs阴沟肠杆菌的流行特征。结果：在42株对第三代头孢菌素或氨曲南敏感性降低的阴沟肠杆菌中，有25株产生ESBLs，占我院同期临床分离的全部阴沟肠杆菌的23．6％（25／106）。其中18株产CTX－M－3，7株产SHV－12，分别占同期我院临床分离的全部阴沟肠杆菌的17．0％（18／106）和6．6％（7／106），这是国内首次报道CTX－M－3和SHV－12在阴沟肠杆菌中广泛流行，产CTX－M－3或SVH－12的阴沟肠杆菌均呈多克隆构成模式，仅个别病区内发生过产CTX－M－3阴沟肠杆菌引起的小型克隆传播。结论：在临床分离的阴沟肠杆菌中，由ESBLs介导的耐药已经成为严重总是。ESBLs的基因型主要为CTX－M－3，而SHV－12也不少见。CTX－M－3和SHV－12在我院的流行主要由其编码基因在不同克隆株之间水平传播引起，克隆传播居次要地位。

Prevalence of CTX-M-3 and SHV-12 extended-spectrum β-Lactamases among clinical isolates of Enterobacter cloacae

Objective To investigate the prevalence, phenotypical characteristics and genotypes of ESBLs among clinical isolates of Enterobacter cloacae from PLA General Hospital. Mehods Among total 106 clinical isolates of Enterobacter cloacae , 42 strains with decreased susceptibilities to ceftazidime, ceftaxime, ceftriaxon or aztreonam were analyzed for the expression of ESBLs. Isoelectric focusing overlay technique and conjugation experiments were used to find ESBLs and determine the phenotypical characteristics of ESBLs. PCR amplification and DNA sequencing were used to determine the genotypes of ESBLs. ERIC PCR typing was used to investigate the epidemiological characteristics of ESBLs producing strains. Results ESBLs were found in 25 isolates, which accounted for 23 6% of total 106 Enterobacter cloacae strains collected from February 1999 to March 2001. Among 25 ESBLs producing strains, 18 strains produced CTX M 3 and 7 strains produced SHV 12. This was the first report of the prevalence of CTX M 3 and SHV 12 among clinical isolates of Enterobacter cloacae in China. ERIC PCR typing revealed the multiclonal constitution of ESBLs producing strains. Conclusion Resistance to third generation cephalosporins mediated by ESBLs has been a serious problem in Enterobacter cloacae. CTX M 3 was the most prevalent ESBL, and SHV 12 was also often found among clinical Enterobacter cloacae isolates. The prevalence of CTX M 3 and SHV 12 was mainly due to horizontal gene spread in our hospital.