Yuejin Zhang, Qingli Chang, Qian Wang, Junwan Lu, Huan Wang, Peizhen Li, Jun Ying, Qiyu Bao, Yunliang Hu
School of Laboratory and Life Sciences, Wenzhou Medical University, Wenzhou 325000, China; School of Nursing, Wenzhou Medical University, Wenzhou 325000, China;
School of Laboratory and Life Sciences, Wenzhou Medical University, Wenzhou 325000, China.
Yi Chuan. 2014 Jun;36(6):603-10. doi: 10.3724/SP.J.1005.2014.0603.
To investigate molecular mechanism of multi-resistance of Klebsiella pneumoniae and its spreading, 179 strains isolated from different clinical samples in the period of 2002-2007 with serious resistance to 14 anti-bacterial agents were examined. Among them, 118 (65.9%) were resistant to at least two anti-bacterial agents; 36.3% (65/179) were found to contain class 1 integrons. There was a significant difference for resistance rate between the integron positive and the negative groups, especially for antimicrobial agents of aminoglycosides, quinolones and sulfonamides (P<0.01). Gene cassette structures of the class 1 integrons in these bacteria were analyzed and their resistance genes were further cloned and tested for antibiotic resistance activities. Fifteen gene cassettes were identified with dfrA17-aadA5 being the most popular form. Three recombinant plasmids pET28a-dhfr17, pET28a-dhfr17-orfF and pET28a-dhfr17-orfF-aadA2 were cloned from a gene cassette of dhfr17-orfF-aadA2. When introduced into a recipient E. coli strain BL21, all of them rendered resistance to co-trimoxazole, with minimum inhibitory concentration (MIC) value up to 256 µg/µL. The E. coli BL21 carrying pET28a- dhfr17 or pET28a-dhfr17-orfF had the same MIC value of 8 µg/µL to streptomycin as the recipient strain without plasmid. However, the E. coli carrying pET28a-dhfr17-orfF-aadA2 was resistant to streptomycin with MIC level up to 256 µg/µL. In conclusion, class 1 integrons were regularly identified in Klebsiella pneumoniae. They mainly carry resistance genes against antimicrobial agents of aminoglycosides and sulfonamide. Transferable plasmid carrying integrons with resistance genes may play an important role in resistance spreading among bacterial species.
为研究肺炎克雷伯菌多重耐药及其传播的分子机制，对2002年至2007年期间从不同临床样本中分离出的179株对14种抗菌药物具有严重耐药性的菌株进行了检测。其中，118株（65.9%）对至少两种抗菌药物耐药；36.3%（65/179）被发现含有1类整合子。整合子阳性组和阴性组的耐药率存在显著差异，尤其是对氨基糖苷类、喹诺酮类和磺胺类抗菌药物（P<0.01）。分析了这些细菌中1类整合子的基因盒结构，并进一步克隆了它们的耐药基因并检测其抗生素耐药活性。鉴定出15个基因盒，其中dfrA17-aadA5是最常见的形式。从dhfr17-orfF-aadA2基因盒中克隆了3种重组质粒pET28a-dhfr17、pET28a-dhfr17-orfF和pET28a-dhfr17-orfF-aadA2。当将它们导入受体大肠杆菌菌株BL21时，所有菌株均对复方新诺明产生耐药性，最低抑菌浓度（MIC）值高达256μg/μL。携带pET28a-dhfr17或pET28a-dhfr17-orfF的大肠杆菌BL21对链霉素的MIC值与无质粒的受体菌株相同，均为8μg/μL。然而，携带pET28a-dhfr17-orfF-aadA2的大肠杆菌对链霉素耐药，MIC水平高达256μg/μL。总之，在肺炎克雷伯菌中经常鉴定出1类整合子。它们主要携带针对氨基糖苷类和磺胺类抗菌药物的耐药基因。携带耐药基因整合子的可转移质粒可能在细菌物种间的耐药传播中起重要作用。
