Department of Biotechnology, University of North Bengal, Siliguri, West Bengal, India.
Ann Clin Microbiol Antimicrob. 2011 May 19;10:19. doi: 10.1186/1476-0711-10-19.
The aim of this study was to describe a novel trimethoprim resistance gene cassette, designated dfrA30, within a class 1 integron in a facultatively oligotrophic, multiple antibiotic and human serum resistant test strain, MB45, in a population of oligotrophic bacteria isolated from the river Mahananda; and to test the efficiency of surface bound acetate on zinc oxide quantum dots (ZnO QDs) as bactericidal agent on MB45.
Diluted Luria broth/Agar (10-3) media was used to cultivate the oligotrophic bacteria from water sample. Multiple antibiotic resistant bacteria were selected by employing replica plate method. A rapid assay was performed to determine the sensitivity/resistance of the test strain to human serum. Variable region of class 1 integron was cloned, sequenced and the expression of gene coding for antibiotic resistance was done in Escherichia coli JM 109. Identity of culture was determined by biochemical phenotyping and 16S rRNA gene sequence analyses. A phylogenetic tree was constructed based on representative trimethoprim resistance-mediating DfrA proteins retrieved from GenBank. Growth kinetic studies for the strain MB45 were performed in presence of varied concentrations of ZnO QDs.
The facultatively oligotrophic strain, MB45, resistant to human serum and ten antibiotics trimethoprim, cotrimoxazole, ampicillin, gentamycin, netilmicin, tobramycin, chloramphenicol, cefotaxime, kanamycin and streptomycin, has been identified as a new strain of Klebsiella pneumoniae. A novel dfr gene, designated as dfrA30, found integrated in class 1 integron was responsible for resistance to trimethoprim in Klebsiella pneumoniae strain MB45. The growth of wild strain MB45 was 100% arrested at 500 mg/L concentration of ZnO QDs. To our knowledge this is the first report on application of ZnO quantum dots to kill multiple antibiotics and serum resistant K. pneumoniae strain.
本研究旨在描述一种新型的三甲氧嘧啶耐药基因盒，命名为 dfrA30，它存在于一个类 1 整合子中，该整合子位于一种兼性寡营养、多种抗生素和人血清抗性试验菌株 MB45 中，该菌株存在于从马汉丹那河分离的寡营养细菌群体中；并测试表面结合的醋酸盐在氧化锌量子点 (ZnO QDs) 上作为杀菌剂对 MB45 的效率。
用稀释的 Luria 肉汤/琼脂（10-3）培养基从水样中培养寡营养细菌。采用复制平板法选择多重抗生素耐药菌。采用快速检测法测定试验菌株对人血清的敏感性/耐药性。克隆、测序类 1 整合子的可变区，并在大肠杆菌 JM 109 中表达编码抗生素耐药性的基因。通过生化表型和 16S rRNA 基因序列分析确定培养物的身份。根据从 GenBank 中检索到的代表性三甲氧嘧啶耐药介导 DfrA 蛋白构建系统发育树。在不同浓度的 ZnO QDs 存在下，对 MB45 菌株进行生长动力学研究。
已鉴定出一种兼性寡营养菌株 MB45，该菌株对人血清和十种抗生素（三甲氧嘧啶、复方新诺明、氨苄西林、庆大霉素、奈替米星、妥布霉素、氯霉素、头孢噻肟、卡那霉素和链霉素）具有耐药性，被鉴定为一种新的肺炎克雷伯菌。一种新型的 dfr 基因，命名为 dfrA30，发现整合在类 1 整合子中，是导致肺炎克雷伯菌 MB45 对三甲氧嘧啶耐药的原因。野生型 MB45 菌株的生长在 500mg/L ZnO QDs 浓度下 100%被抑制。据我们所知，这是首次应用 ZnO 量子点杀死多种抗生素和血清耐药的肺炎克雷伯菌的报道。
