Zhong Xue, Xu Hongtao, Chen Dongke, Zhou Haijian, Hu Xin, Cheng Gang
Department of Pharmaceutics, School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, Liaoning, PR China; Department of Pharmacy, Beijing Hospital, Beijing, PR China.
Department of Clinical Laboratory, Beijing Hospital, Beijing, PR China.
PLoS One. 2014 Dec 12;9(12):e115185. doi: 10.1371/journal.pone.0115185. eCollection 2014.
Tigecycline is one of the few therapeutic options for treating infections caused by some multi-drug resistant pathogens, such as Klebsiella pneumoniae. However, tigecycline-resistant K. pneumoniae has been discovered recently in China. From 2009 to 2013, nine tigecycline-resistant K. pneumoniae isolates were identified in our hospital. Six of nine strains were identified before using tigecycline. To investigate the efflux-mediated resistance mechanisms of K. pneumoniae, the expression of efflux pump genes (acrA, acrB, tolC, oqxA and oqxB) and pump regulators (acrR, marA, soxS, rarA, rob and ramA) were examined by real-time RT-PCR. Molecular typing of the tigecycline resistant strains was performed. ST11 was the predominant clone of K. pneumoniae strains, while ST1414 and ST1415 were novel STs. Efflux pump inhibitor (EPI)-carbonyl cyanide chlorophenylhydrazone (CCCP) was able to reverse the resistance patterns of 5 resistant K. pneumoniae strains. In comparison with strain A111, a tigecycline-susceptible strain (negative control), we found that the expression levels of efflux pump genes and pump regulators were higher in a majority of resistant strains. Higher expression levels of regulators rarA (2.41-fold, 9.55-fold, 28.44-fold and 18.31-fold, respectively) and pump gene oqxB (3.87-fold, 31.96-fold, 50.61-fold and 29.45-fold, respectively) were observed in four tigecycline resistant strains (A363, A361, A368, A373, respectively). Increased expression of acrB was associated with ramA and marA expression. To our knowledge, studies on tigecycline resistance mechanism in K. pneumoniae are limited especially in China. In our study, we found that both efflux pump AcrAB-TolC and OqxAB contributed to tigecycline resistance in K. pneumoniae isolates.
替加环素是治疗由某些多重耐药病原体（如肺炎克雷伯菌）引起的感染的少数治疗选择之一。然而，最近在中国发现了对替加环素耐药的肺炎克雷伯菌。2009年至2013年期间，我院鉴定出9株对替加环素耐药的肺炎克雷伯菌分离株。9株菌株中有6株是在使用替加环素之前鉴定出来的。为了研究肺炎克雷伯菌外排介导的耐药机制，通过实时逆转录聚合酶链反应检测了外排泵基因（acrA、acrB、tolC、oqxA和oqxB）和泵调节因子（acrR、marA、soxS、rarA、rob和ramA）的表达。对替加环素耐药菌株进行了分子分型。ST11是肺炎克雷伯菌菌株的主要克隆型，而ST1414和ST1415是新的序列型。外排泵抑制剂（EPI）-羰基氰化物间氯苯腙（CCCP）能够逆转5株对替加环素耐药的肺炎克雷伯菌菌株的耐药模式。与替加环素敏感菌株A111（阴性对照）相比，我们发现大多数耐药菌株中外排泵基因和泵调节因子的表达水平更高。在4株对替加环素耐药的菌株（分别为A363、A361、A368、A373）中，观察到调节因子rarA的表达水平分别升高了2.41倍、9.55倍、28.44倍和18.31倍，泵基因oqxB的表达水平分别升高了3.87倍、31.96倍、50.61倍和29.45倍。acrB表达的增加与ramA和marA的表达相关。据我们所知，关于肺炎克雷伯菌对替加环素耐药机制的研究尤其是在中国还很有限。在我们的研究中，我们发现外排泵AcrAB-TolC和OqxAB均对肺炎克雷伯菌分离株对替加环素的耐药性有贡献。
