Filgona Joel, Banerjee Tuhina, Anupurba Shampa
Institute of Medical Science, Banaras Hindu University, India.
J Infect Dev Ctries. 2015 Aug 29;9(8):815-20. doi: 10.3855/jidc.6216.
The contribution of efflux systems to drug resistance in Enterobacteriaceae is becoming increasingly appreciated. This study phenotypically analyzed the role of efflux mechanisms in resistance to ertapenem, doripenem, and tigecycline among clinical isolates of carbapenem-resistant Klebsiella pneumoniae (CRKP).
Multidrug-resistant and carbapenem non-susceptible K. pneumoniae isolates were determined by disk diffusion test. Further susceptibility of these isolates to carbapenems, ceftriaxone, cefoperazone, ceftazidime, tigecycline, and colistin was determined by agar dilution assay, and CRKP was identified. While modified Hodge test was used to confirm carbapenemase production, the contribution of efflux mechanisms was determined by a minimum inhibitory concentration (MIC) reduction assay, and typing was done by enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction (PCR).
Of the 238 isolates of K. pneumoniae, 174 were multidrug resistant and 74 were CRKP. Forty of the CRKP were positive for carbapenemase production, while 43, 11, and 2 of the CRKP isolates had elevated MIC of ≥ 32 µg/mL for ertapenem, doripenem, and tigecycline, respectively. Twofold or higher MIC reduction to ertapenem, doripenem, and tigecycline was observed in 6, 28, and 27 isolates, respectively; however, non-susceptibility to ertapenem, doripenem and tigecycline was abolished in 2, 11, and 18 K. pneumoniae isolates, respectively. Nine clones of CRKP widely distributed within the hospital were obtained from ERIC PCR.
Although colistin retained better activity against CRKP, efflux pumps contributed to increased MIC in ertapenem, doripenem, and tigecycline. Therefore, efflux systems are important aspects that should be explored in the fight against multidrug-resistant bacteria.
外排系统对肠杆菌科细菌耐药性的影响日益受到重视。本研究对外表型分析了耐碳青霉烯类肺炎克雷伯菌（CRKP）临床分离株中，外排机制在对厄他培南、多利培南和替加环素耐药性方面所起的作用。
采用纸片扩散法测定多重耐药和对碳青霉烯类不敏感的肺炎克雷伯菌分离株。通过琼脂稀释法进一步测定这些分离株对碳青霉烯类、头孢曲松、头孢哌酮、头孢他啶、替加环素和黏菌素的敏感性，并鉴定出CRKP。采用改良 Hodge 试验确认碳青霉烯酶的产生，通过最低抑菌浓度（MIC）降低试验确定外排机制的作用，并采用肠杆菌重复基因间共识（ERIC）聚合酶链反应（PCR）进行分型。
在 238 株肺炎克雷伯菌分离株中，174 株为多重耐药，74 株为 CRKP。40 株 CRKP 碳青霉烯酶产生呈阳性，而分别有 43 株、11 株和 2 株 CRKP 分离株对厄他培南、多利培南和替加环素的 MIC 升高至≥32μg/mL。分别在 6 株、28 株和 27 株分离株中观察到对厄他培南、多利培南和替加环素的 MIC 降低两倍或更高；然而，分别有 2 株、11 株和 18 株肺炎克雷伯菌分离株对厄他培南、多利培南和替加环素的不敏感性被消除。通过 ERIC PCR 获得了在医院内广泛分布的 9 个 CRKP 克隆。
尽管黏菌素对 CRKP 仍保持较好的活性，但外排泵导致了对厄他培南、多利培南和替加环素的 MIC 升高。因此，外排系统是对抗多重耐药菌时应探索的重要方面。
