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鲍曼不动杆菌临床分离株中的多种碳青霉烯水解基因。

Multiple carbapenem hydrolyzing genes in clinical isolates of Acinetobacter baumannii.

作者信息

Niranjan D K, Singh N P, Manchanda V, Rai S, Kaur I R

机构信息

Department of Microbiology, University College of Medical Sciences and Guru Teg Bahadur Hospital, Dilshad Garden, New Delhi, India.

出版信息

Indian J Med Microbiol. 2013 Jul-Sep;31(3):237-41. doi: 10.4103/0255-0857.115626.

Abstract

PURPOSE

Carbapenem resistance in Acinetobacter baumannii has become highly rampant, which has been ascribed to the presence of multiple carbapenemases. The objective of the present study was to prospectively investigate the presence of multiple carbapenemase encoding genes in clinical isolates of A. baumannii.

MATERIALS AND METHODS

A total of 30 imipenem resistant, consecutive non-repeat clinical isolates A. baumannii from a Tertiary Care Centre of Delhi were subjected to antimicrobial susceptibility testing (AST), screening for carbapenemase production by modified Hodge test (MHT) and determination of minimum inhibitory concentration for imipenem by E-Test® . These were subjected to Real time PCR for blaIMP-1 and 2 , blaVIM-1 and 2, blaOXA23, 24, 51 and 58 using SYBR green-I. These were grouped together on the basis of their genotype as each isolate harboured multiple carbapenemases and correlated with their AST profile. Detection of the novel carbapenemase blaNDM-1 was performed by real time PCR using TaqMan probes on 14 isolates.

RESULTS

Colistin appeared to be the most effective drug in vitro, followed by tetracycline and beta lactam/beta lactamase inhibitor combinations. All, but one isolate were positive for the MHT. All 30 isolates were positive for blaOXA-51 like gene as well as blaIMP-1 and blaVIM-1 genes. blaOXA 24 and 58 were not detected in any of the isolates. blaIMP-2 , blaVIM-2 , blaOXA-23 were present in 15, 6 and 14 isolates respectively. Grouping based on the genotypic profile did not correlate with susceptibility pattern. Nine among the 14 isolates also harboured the novel blaNDM-1 gene.

CONCLUSIONS

This is the first study from North India, which comprehensively detected the presence of multiple carbapenemases as well the blaNDM-1 gene. The presence of the novel gene blaNDM-1 indicated ability of A. baumannii to acquire new carbapenemase genes despite the existence of multiple carbapenemase genes. The present study confirmed the presence of multiple genetic mechanisms for carbapenemases production among the clinical isolates of A. baumannii in north India.

摘要

目的

鲍曼不动杆菌对碳青霉烯类抗生素的耐药性已变得极为猖獗,这归因于多种碳青霉烯酶的存在。本研究的目的是前瞻性地调查鲍曼不动杆菌临床分离株中多种碳青霉烯酶编码基因的存在情况。

材料与方法

从德里一家三级医疗中心收集了30株对亚胺培南耐药、连续且无重复的鲍曼不动杆菌临床分离株,进行抗菌药物敏感性试验(AST)、采用改良 Hodge 试验(MHT)筛选碳青霉烯酶的产生情况以及用 Etest® 测定亚胺培南的最低抑菌浓度。使用 SYBR green-I 对这些分离株进行 blaIMP-1 和 2、blaVIM-1 和 2、blaOXA23、24、51 和 58 的实时荧光定量 PCR。由于每个分离株都含有多种碳青霉烯酶,根据其基因型将它们分组,并与它们的 AST 谱相关联。使用 TaqMan 探针通过实时荧光定量 PCR 对14株分离株检测新型碳青霉烯酶 blaNDM-1。

结果

黏菌素似乎是体外最有效的药物,其次是四环素和β-内酰胺/β-内酰胺酶抑制剂组合。除一株分离株外,所有分离株的 MHT 均呈阳性。所有30株分离株的 blaOXA-51 样基因以及 blaIMP-1 和 blaVIM-1 基因均呈阳性。在任何分离株中均未检测到 blaOXA 24 和 58。blaIMP-2、blaVIM-2、blaOXA-23 分别存在于15株、6株和14株分离株中。基于基因型谱的分组与药敏模式不相关。14株分离株中有9株还携带新型 blaNDM-1 基因。

结论

这是北印度的第一项研究,全面检测了多种碳青霉烯酶以及 blaNDM-1 基因的存在情况。新型基因 blaNDM-1 的存在表明,尽管存在多种碳青霉烯酶基因,鲍曼不动杆菌仍有获取新碳青霉烯酶基因的能力。本研究证实了印度北部鲍曼不动杆菌临床分离株中存在多种产生碳青霉烯酶的遗传机制。

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