肠球菌属细菌高水平庆大霉素耐药及其转座子的检测

目的研究2006—2009年北京地区临床分离高水平庆大霉素耐药(HLGR)肠球菌属细菌的双功能修饰酶基因转座子结构。方法采用脑心肉汤微稀释法测定北京地区169株临床分离粪肠球菌和21株屎肠球菌的高水平庆大霉素耐药性,应用菌落PCR扩增方法检测HLGR菌株中双功能修饰酶基因及两端插入序列(IS256),分析转座子结构。结果 169株粪肠球菌中,111株(65.7%)为HLGR株,HLGR菌中97.3%含有双功能修饰酶基因,其中10.2%含有完整结构的转座子(双功能修饰酶基因两端均含有IS256插入序列),89.8%含有截断结构的转座子(缺失一端或两端的插入序列)。21株屎肠球菌中,15株(71.4%)为HLGR株,所有HLGR菌株均含有双功能修饰酶基因,其中13.3%含有完整结构的转座子,86.7%含有截断结构的转座子。结论 2006—2009年北京地区临床分离肠球菌HLGR率高,并且绝大多数HLGR株含双功能修饰酶基因,通常形成截断结构的转座子。

Detection of transposons conferring high level gentamicin resistance in Enterococcus

Objective To characterize the structures of transposons containing the bifunctional aminoglycoside modifying enzyme gene aac(6 )-aph(2 ) in high level gentamicin-resistant(HLGR) clinical strains of Enterococcus isolated in Beijing.Methods Totally 169 randomly selected Enterococcus faecalis strains and 21 randomly selected Enterococcus faecium strains collected from hospitals in Beijing from 2006 to 2009 were included in the present study.HLGR was determined by broth microdilution method according to CLSI standards.The bifunctional aminoglycoside modifying enzyme gene and the insertion sequence IS256 on both sides were detected by colony PCR.The structure of the transposons was analyzed.Results Among the 169 Enterococcus faecalis.111(65.7%) were identified as high-level gentamicin resistant.The bifunctional aminoglycoside modifying enzyme gene was detected in 108(97.3%) of the 111 HLGR isolates.Of the bifunctional aminoglycoside modifying enzyme gene positive isolates,11(10.2%) carried intact transposon with IS256 at flanking sides of the bifunctional aminoglycoside modifying enzyme gene.The remaining strains(89.8%) carried truncated transposon(loss of IS256 at one or both sides).High-level gentamicin resistance was confirmed in 71.4%(15/21) of the Enterococcus faecium strains.All the 15 strains carried aac (6’)-Ie-aph(2")-Ia.Intact transposon structure was identified in 13.3%(2/15),and truncated transposon in 86.7%(13/15) of the strains.Conclusions The prevalence of HLGR is high in the clinical strains of Enterococcus collected during 2006 and 2009 in Beijing,China.The bifunctional aminoglycoside modifying enzyme gene was identified in most of the HLGR strains. The transposons containing the bifunctional aminoglycoside modifying enzyme gene are usually truncated.