OXA-51样D类碳青霉烯酶在鲍曼不动杆菌中广泛分布

Wide dissemination of OXA-51-like type of carbapenemase in Acinetobacter baumannii

目的研究全国7家教学医院临床分离的美罗培南敏感与非敏感鲍曼不动杆菌中碳青霉烯酶类型及其分布特点。方法收集2005年北京协和医院、北京朝阳医院、解放军第三○四医院和大连、浙江、南京医院临床分离存活的非重复的美罗培南非敏感不动杆菌126株,并分别从北京协和医院、北京医院、浙江、大连、南京5家医院选取美罗培南敏感的19株菌作为对照,采用琼脂稀释法测定这些菌株对美罗培南、亚胺培南等抗菌药物的 MIC;用多重 PCR、测序等方法分析鲍曼不动杆菌中 OXA-23-like、OXA-24-like 和 OXA-58-like 及 OXA-51-like 4个亚组的碳青霉烯酶分布特点。结果收集145株临床非重复的鲍曼不动杆菌,采用多重 PCR 方法检测出 bla_(OXA-51-like)基因127株(87.6%),美罗培南非敏感126株菌中,bla_(OXA-23-like)基因8株,bla_(OXA-23-like)与 bla_(OXA-51-like)基因同时存在的65株(51.6%)bla_(OXA-24-like)基因1株、bla_(OXA-58-like)基因3株。以不同医院为单位,依据药敏谱型挑选4种酶型阳性代表株,分别进行全长引物测定,序列分析 bla_(OXA-24-like)。确定为 OXA-72;3株 bla_(OXA-58-like)确定为OXA-58;15株 bla_(OXA-23-like)确定为 OXA-23;13株 bla_(OXA-51-like)测序结果12株为 OXA-51等位基因 OXA-66,1株为 OXA-68。结论研究结果表明 OXA-66/OXA-51样碳青霉烯酶以最普遍存在的方式广泛分布于鲍曼不动杆菌中。

Objective To investigate the dissemination of carbapenemase type and the genetic relationship of Acinetobacter baumannii clinical isolates recovered in seven teaching hospitals in China. Methods Non-repetitive 145 meropenem susceptible and non-susceptible Acinetobacter baumanii clinical isolates were collected in Beijing, Zhejiang, Nanjing and Dalian in 2005. Minimum inhibitory concentrations （MIC） of meropenem, imipenem and other antibiotics were determined by agar dilution. A novel multiplex polymerase chain reaction （PCR） assay were used to detect and distinguish alleles encoding three subgroups of acquired OXA carbapenemases （OXA-23-1ike, OXA-24-1ike and OXA-58-1ike） that are scattered in Acinetobacter spp. , and a fourth subgroup, OXA-51-1ike, which appears to be intrinsic to Acinetobacter baumannii. Results Genes encoding blaOXA-51-like were detected in 127 （ 87. 6% ） in all of 145 isolates. Among 126 meropenem-non-susceptible strains, blaOXA-23-like gene was detected in 8 isolates, blaOXA-23-likecombined with blaOXA-51-likegenes in 65 isolates,blaOXA-24-likegene in 1 isolate and blaOXA-58-like gene in 3 isolates. Sequence analysis of the products from different hospitals and antimicrobial susceptibility testing of blaOXA--51-like amplicons （ 13cases ） identified blaOXA-66（ 12 cases ） and blaOXA-68 （ lcase ）. Gene encoding blaOXA-58-like identified as blaOXA-58, and genes encoding blaOXA-240-like was blaoxA,72, blaOXA-23-like （ 15 cases ） sequences were classical blaOXA-23. Condusion These findings indicate wide dissemination of OXA-66/ OXA-51 type of carbapenemases and naturally present in almost all A. baumannii isolates.