Rajpara Neha, Nair Mrinalini, Bhardwaj Ashima Kushwaha
1Department of Human Health and Diseases, Indian Institute of Advanced Research, Koba Institutional Area, Gandhinagar, Gujarat 382 007 India.
Department of Microbiology and Biotechnology Centre, Maharaja Sayaji Rao University of Baroda, Vadodara, Gujarat 390002 India.
Indian J Microbiol. 2018 Mar;58(1):60-67. doi: 10.1007/s12088-017-0687-8. Epub 2017 Oct 31.
In an earlier study from this laboratory, BD146, a clinical isolate from Kolkata, India, 2002, was found to be resistant to all the fourteen antibiotics tested. It harboured a high copy number plasmid pBD146 and a low copy number plasmid. In the present study, a more detailed analysis was carried out to unravel different resistance mechanisms in this isolate. Sequencing showed that variable region of class 1 integron located on low copy number plasmid harbored 3-A--A1 gene cassettes. Analysis for extended spectrum beta lactamases (ESBLs) revealed that BD146 was ESBL positive. Efflux pumps were involved in the drug resistance phenotype for chloramphenicol, kanamycin, streptomycin and tetracycline. Sequence analysis of pBD146 revealed the presence of genes encoding an integrase with a unique sequence having little similarity to other known integrases, toxin-antitoxin (), a replicase, trimethoprim resistance () and quinolone resistance (). Presence of A, putative novel integrase and toxin-antitoxin system in has been documented for the first time in this report. pBD146 showed 99% sequence similarity with pVN84 from O1 of Vietnam, 2004 and a plasmid from v110 of Hong Kong, 2010. Conjugation experiments proved the ability of pBD146 and the low copy number plasmid, to get transferred to another host imparting their antibiotic resistance traits to the transconjugants. Therefore, present study has indicated that plasmids played an important role for dissemination of drug resistance.
在本实验室早期的一项研究中,BD146(2002年从印度加尔各答分离出的临床菌株)对所测试的全部14种抗生素均具有抗性。它携带一个高拷贝数质粒pBD146和一个低拷贝数质粒。在本研究中,进行了更详细的分析以阐明该菌株中的不同抗性机制。测序表明,位于低拷贝数质粒上的1类整合子可变区含有3个A--A1基因盒。对超广谱β-内酰胺酶(ESBLs)的分析显示BD146为ESBL阳性。外排泵参与了氯霉素、卡那霉素、链霉素和四环素的耐药表型。pBD146的序列分析揭示了编码一种整合酶的基因的存在,该整合酶具有独特序列,与其他已知整合酶几乎没有相似性,还有毒素-抗毒素()、一种复制酶、甲氧苄啶抗性()和喹诺酮抗性()。本报告首次记录了在中存在A、推定的新型整合酶和毒素-抗毒素系统。pBD146与2004年越南O1的pVN84以及2010年中国香港v110的一个质粒显示出99%的序列相似性。接合实验证明了pBD146和低拷贝数质粒能够转移到另一个宿主,将其抗生素抗性特性赋予接合子。因此,本研究表明质粒在耐药性传播中发挥了重要作用。