Bhattacharjee A, Sen M R, Prakash P, Gaur A, Anupurba S, Nath G
Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221 005, India.
Indian J Med Microbiol. 2010 Jul-Sep;28(3):207-10. doi: 10.4103/0255-0857.66472.
Klebsiella pneumoniae is considered an important pathogen causing nosocomial and community-acquired infections and is often associated with the production of extended-spectrum beta-lactamases (ESBL) belonging to SHV and CTX-M families, which are frequently described as a part of complex integrons, facilitate their horizontal transfer to other related as well as unrelated microbes. The present study was undertaken to investigate the occurrence and characterization of integrons among K pneumoniae isolates producing ESBL in a tertiary referral hospital.
A total of 136 clinical isolates of K pneumoniae were investigated for the presence of ESBL. Their ESBL genes were characterized by multiplex polymerase chain reaction (PCR). Integrase gene PCR was performed to detect the presence of integron. The isolates were further typed by random amplification of polymorphic DNA (RAPD).
Out of 136 K pneumoniae isolates, 63 (46%) were confirmed to be ESBL producers. SHV (68%) and CTX-M (67%) ESBL genes were the most common in our study. Of the 63 ESBL-positive isolates, 58 (92%) strains carried integrons; 52 strains (82%) carried only class 1 integron, whereas 6 (9%) isolates harboured both class 2 integrons and the class 1 gene. However, in ESBL negatives, only 29 (40%) strains were positive for class 1 integron and none for class 2 integron.
The presence of class 2 integron amongst ESBL-producing K pneumoniae is being described for the first time in this part of the world. The findings of this study strongly suggest that integrons have a role in the dissemination of ESBL-mediated resistance among the nosocomial isolates of K pneumonia.
肺炎克雷伯菌被认为是引起医院感染和社区获得性感染的重要病原菌，且常与属于SHV和CTX-M家族的超广谱β-内酰胺酶（ESBL）的产生相关，这些酶常被描述为复杂整合子的一部分，有助于它们向其他相关及不相关微生物进行水平转移。本研究旨在调查一家三级转诊医院中产生ESBL的肺炎克雷伯菌分离株中整合子的发生情况及特征。
共对136株肺炎克雷伯菌临床分离株进行ESBL检测。通过多重聚合酶链反应（PCR）对其ESBL基因进行特征分析。进行整合酶基因PCR以检测整合子的存在。通过随机扩增多态性DNA（RAPD）对分离株进一步分型。
在136株肺炎克雷伯菌分离株中，63株（46%）被确认为ESBL生产者。SHV（68%）和CTX-M（67%）ESBL基因在我们的研究中最为常见。在63株ESBL阳性分离株中，58株（92%）携带整合子；52株（82%）仅携带1类整合子，而6株（9%）分离株同时含有2类整合子和1类基因。然而，在ESBL阴性株中，仅29株（40%）1类整合子呈阳性，2类整合子均为阴性。
在世界这一地区首次描述了产ESBL的肺炎克雷伯菌中存在2类整合子。本研究结果强烈表明，整合子在肺炎克雷伯菌医院分离株中ESBL介导的耐药性传播中起作用。
