鲍曼不动杆菌OXA基因的检测及ISAba1对其表达的影响

Detection of OXA gene in A. baumanii and effect of ISAba1 to resistance of Imipenem mediated by OXA-23 in A. baumanii

关键词:  鲍曼不动杆菌  碳青霉烯酶  插入序列  亚胺培南  转化

Key words:  Acinetobacter baumannii  carbapenemases  ISAba1  Imipenem  transformation

摘要:

[目的]了解鲍曼不动杆菌的OXA-碳青霉烯酶基因分布情况及插入序列1（ISAba1）对OXA-23基因表达的影响。[方法]收集临床分离的鲍曼不动杆菌无重复株110株。多重PCR扩增OXA-23-like、OXA-24-like、OXA-51-like、OXA-58-like基因，并测序；应用肠杆菌科基因组内重复序列ERIC-PCR进行同源性分析。PCR扩增OXA-23、OXA-51、 ISAba1-OXA-23和ISAba1-OXA-51，并用大肠杆菌TOP10进行转化OXA-23、 ISAba1-OXA-23、OXA-51。琼脂稀释法测定阳性菌株和转化子TOP10（pGM -OXA）对亚胺培南的MIC值。[结果]在上述临床菌株中PCR检测出blaOXA-23、blaOXA-51 、blaOXA-58、ISAba1-OXA-23，未检测到blaOXA-24、ISAba1-OXA-51; 110株鲍曼不动杆菌来自18个不同克隆株;转化子TOP10（pGM -ISAba1-OXA-23）MIC值为0.5，另一转化子TOP10（pGM-OXA-23）MIC值为0.125，TOP10（pGM-OXA-51）MIC值为0.25,三者均未显示对亚胺培南高水平耐药的特性。[结论]OXA-碳青霉烯酶基因在鲍曼不动杆菌中广泛存在，以OXA-23、OXA-51为主；同时携带OXA-23和OXA-51两种基因的鲍曼不动杆菌较多见； ISAba1位于OXA-23基因的上游；其在大肠杆菌中并未对OXA酶的表达产生大的影响。

Abstract:

[Objective] To study the distribution of OXA genes of A. baumanii and the effect of ISAba1 on gene expression of OXA-23. [Methods] A total of 110 non-replicate Acinetobacter baumannii strains were isolated from clinical specimens. OXA-23-like, OXA-24-like, OXA-51-like, OXA-58-like genes were amplified by multiplex PCR. The PCR products were sequenced. Homology was analyzed by ERIC-PCR. OXA-23, OXA-51, ISAba1-OXA-23 and ISAba1-OXA-51 were amplified by PCR. OXA-23, ISAba1-OXA-23 and OXA-51 were transformed into Escherichia coli TOP10. The minimal inhibitory concentrations (MIC) of the positives isolates and the products of the transformation to Imipenem were determined using ager dilution. [Results] The genes blaOXA-23, blaOXA-51, blaOXA-58, ISAba1-OXA-23 except blaOXA-24 and ISAba1-OXA-51 were detected in the clinical strains by PCR. One hundred and ten strains of acinetobacter baumannii came from 18 different clones. MIC of the transformation TOP10 （pGM- ISAba1-OXA-23） was 0.5, while the MIC of the other TOP10 （pGM -OXA-23）was 0.125, and the MIC of the other TOP10（pGM -OXA-51） was 0.25. Three of them did not exhibit high-level resistance to Imipenem. [Conclusions] OXA genes are widespread in A. baumanii, most of them are OXA-23 and OXA-51. Acinetobacter baumannii with OXA-23 gene and OXA-51 gene are more common in clinic. ISAba1 is in upstream OXA- 23, it does not affect the express of OXA-23 so much when it is in Escherichia coli.