Pakzad Iraj, Zayyen Karin Maasoume, Taherikalani Morovat, Boustanshenas Mina, Lari Abdolaziz Rastegar
Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran.
GMS Hyg Infect Control. 2013 Nov 6;8(2):Doc15. doi: 10.3205/dgkh000215. eCollection 2013.
Resistance to fluoroquinolones has been recently increased among bacterial strains isolated from outpatients. Multidrug-resistant K. pneumoniae is one of the major organisms isolated from burn patients and the AcrAB efflux pump is the principal pump contributing to the intrinsic resistance in K. pneumoniae against multiple antimicrobial agents including ciprofloxacin and other fluoroquinolones. Fifty-two K. pneumoniae isolated from burn patients in Shahid Motahari hospital and confirmed by conventional biochemical tests. Antimicrobial susceptibility testing was done according to CLSI 2011 guidelines, to determine the antimicrobial resistance pattern of isolates. AcrA gene was detected among ciprofloxacin-resistant isolates by PCR assay. MICs to ciprofloxacin were measured with and without carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Forty out of the 52 K. pneumoniae isolated from burn patients in Shahid Motahari hospital were resistant to ciprofloxacin according to breakpoint of CLSI guideline. PCR assay for acrA gene demonstrated that all ciprofloxacin-resistant isolates harbored acrA gene coding the membrane fusion protein AcrA and is a part of AcrAB efflux system. Among these isolates, 19 strains (47.5%) showed 2 to 32 fold reduction in MICs after using CCCP as an efflux pump inhibitor. The other 21 strains (52.5%) showed no disparity in MICs before and after using CCCP. In conclusion, the AcrAB efflux system is one of the principal mechanisms contribute in ciprofloxacin resistance among K. pneumoniae isolates but there are some other mechanisms interfere with ciprofloxacin resistance such as mutation in target proteins of DNA gyrase of topoisomerase IV enzymes.
近期，从门诊患者中分离出的细菌菌株对氟喹诺酮类药物的耐药性有所增加。多重耐药肺炎克雷伯菌是从烧伤患者中分离出的主要病原体之一，AcrAB外排泵是导致肺炎克雷伯菌对包括环丙沙星和其他氟喹诺酮类药物在内的多种抗菌药物产生固有耐药性的主要泵。从沙希德·莫塔哈里医院的烧伤患者中分离出52株肺炎克雷伯菌，并通过传统生化试验进行确认。根据CLSI 2011指南进行药敏试验，以确定分离株的抗菌耐药模式。通过PCR检测环丙沙星耐药分离株中的AcrA基因。在有和没有羰基氰3-氯苯腙（CCCP）的情况下测量对环丙沙星的最低抑菌浓度（MIC）。根据CLSI指南的断点，从沙希德·莫塔哈里医院的烧伤患者中分离出的52株肺炎克雷伯菌中有40株对环丙沙星耐药。对acrA基因的PCR检测表明，所有环丙沙星耐药分离株都含有编码膜融合蛋白AcrA的acrA基因，且该基因是AcrAB外排系统的一部分。在这些分离株中，19株（47.5%）在使用CCCP作为外排泵抑制剂后MIC降低了2至32倍。另外21株（52.5%）在使用CCCP前后MIC没有差异。总之，AcrAB外排系统是肺炎克雷伯菌分离株中环丙沙星耐药的主要机制之一，但还有一些其他机制会干扰环丙沙星耐药，如拓扑异构酶IV酶的DNA回旋酶靶蛋白发生突变。
