An OXA-66/OXA-51-like carbapenemase and possibly an efflux pump are associated with resistance to imipenem in Acinetobacter baumannii
An OXA-66/OXA-51-like carbapenemase and possibly an efflux pump are associated with resistance to imipenem in Acinetobacter baumannii
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DOI：
10.1128/aac.01512-06
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发表时间：
2007-11-01
影响因子：
4.9
通讯作者：
Lin, Jing-Fang
中科院分区：
文献类型：
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作者：
Hu, Wensi S.;Yao, Shu-Man;Lin, Jing-Fang
我们研究了23株临床鲍曼不动杆菌对亚胺培南耐药的机制。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）分析显示，亚胺培南中间体鲍曼不动杆菌（IIAB）和耐亚胺培南鲍曼不动杆菌（IRAB）菌株中存在一个30 kda的蛋白；该蛋白在亚胺培南敏感鲍曼不动杆菌（ISAB）中几乎检测不到。通过双向凝胶电泳和质谱分析，鉴定该蛋白为oxa -51样碳青霉烯酶。与其他近期发现类似，23株临床菌株均存在bla（oxa -51样）基因；然而，通过逆转录酶PCR （RT-PCR）和实时RT-PCR检测，iab和IRAB菌株中bla（oxa -51样）的转录水平高于ISAB菌株。这种变化是由于在iab和IRAB菌株中存在bla（oxa -51样）上游的插入序列ISAba1，而在ISAB菌株中不存在。将在ISAB ab1254和IRAB ab1266中鉴定的bla(OXA-66) （bla（oxa -51样）基因）导入大肠杆菌TOP10细胞后，对亚胺培南的耐药性分别提高了3.95倍和7.90倍。此外，将ISAB ab8和ISAB ab1254及其体外选择的亚胺培南耐药突变体ISAB ab8(r)和ISAB ab1254(r)进行比较，结果显示bla(OXA-66)/bla（oxa -51样）基因序列、基因表达和外膜蛋白谱没有变化。然而，加入羰基氰化物间氯苯腙后，亚胺培南耐药性降低了4至8倍。综上所述，这些结果表明OXA-66/ oxa -51样碳青霉烯酶有助于对亚胺培南的内在抗性；然而，在耐亚胺培南鲍曼不动杆菌中，外排泵的药物输出可能更重要和/或更频繁发生。此外，这是首次报道台湾菌株OXA-66/ oxa -51样碳青霉烯酶赋予鲍曼不动杆菌亚胺培南抗性。
We investigated the mechanisms involved in imipenem resistance in 23 clinical strains of Acinetobacter baumannii. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the presence of a 30-kDa protein in imipenem-intermediate A. baumannii (IIAB) and imipenem-resistant A. baumannii (IRAB) strains; this protein was almost undetectable in imipenem-susceptible A. baumannii (ISAB) strains. The 30-kDa protein was identified as an OXA-51-like carbapenemase using two-dimensional gel electrophoresis and mass spectrometry. Similar to other recent findings, bla(OXA-51-like) genes were found to exist in all 23 clinical strains; however, the transcript levels of bla(OXA-51-like) in the IIAB and IRAB were higher than in the ISAB strains using reverse transcriptase PCR (RT-PCR) and real-time RT-PCR assays. This change was due to the presence of an insertion sequence, ISAba1, upstream of bla(OXA-51-like) in the IIAB and IRAB strains that was not present in the ISAB strains. The introduction of bla(OXA-66) (a bla(OXA-51-like), gene), identified in ISAB ab1254 and IRAB ab1,266, into Escherichia coli TOP10 cells resulted in 3.95-fold and 7.90-fold elevations in resistance to imipenem, respectively. Furthermore, when ISAB ab8 and ISAB ab1254 and their in vitro-selected imipenem-resistant mutants ISAB ab8(r) and ISAB ab1254(r) were compared, the results showed no change in the bla(OXA-66)/bla(OXA-51-like) gene sequences, in expression of the gene, and in the outer membrane protein profiles. However, there was a four- to eightfold reduction in imipenem resistance upon adding carbonyl cyanide m-chlorophenylhydrazone. Taken together, these results suggest that the OXA-66/OXA-51-like carbapenemase contributes to intrinsic resistance to imipenem; however, drug export by an efflux pump may be more important and/or occur more frequently in imipenem-resistant A. baumannii. Furthermore, this is the first report of a Taiwanese strain of an OXA-66/OXA-51-like carbapenemase that confers imipenem resistance in A. baumannii.