Shahcheraghi Fereshteh, Aslani Mohammad Mehdi, Mahmoudi Hassan, Karimitabar Zahra, Solgi Hamid, Bahador Abbas, Alikhani Mohammad Yousef
Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran.
Department of Microbiology, Hamadan University of Medical Sciences, Hamadan, Iran.
J Med Microbiol. 2017 May;66(5):570-576. doi: 10.1099/jmm.0.000467. Epub 2017 May 9.
Enterobacteriaceae is a large family of Gram-negative bacteria that are considered as normal gut flora. They are the most common human pathogens. The main objective of this study was to investigate the carbapenemase genes in clinical isolates of Enterobacteriaceae resistant to carbapenem antibiotics and determine their clonal relationship using pulsed-field gel electrophoresis (PFGE).
In the present study, bacteria were isolated and identified via conventional biochemical tests and API 20NE. Antibiotic susceptibility was evaluated by using the disc diffusion method and MIC was carried out using the E-test. Phenotypic determination of carbapenemases was performed by employing a modified Hodge test (MHT). Carbapenemase genes including IMP, VIM, KPC, NDM and OXA-48 were amplified by PCR. The relationships between their clonal types with l restriction enzyme were examined using PFGE.
Out of 40 isolates that were resistant or moderately susceptible to carbapenem antibiotics, 29 (72.5 %) strains were positive for carbapenem enzymes phenotypically. Moreover, six isolates contained carbapenemase genes including IMP, VIM, NDM and OXA-48, but the KPC gene was not found in any of the isolates. PFGE results showed that E. coli strains in our area were clustered into eight pulsotypes (A-H), Klebsiella spp. isolates five pulsotypes (A-E) and Proteus spp. had two pulsotypes (A, B). The high resistance to antimicrobial agents in the A, B and F pulsotypes was attributed to E. coli clinical isolates.
Our results could reflect some hospital multidrug-resistant strains in nosocomial infections. The widespread emergence of carbapenem-resistant isolates has caused increasing concern in recent years. Therefore, specific strategies should be designed and evaluated for the control of resistant strains.
肠杆菌科是一大类革兰氏阴性菌，被视为正常肠道菌群。它们是最常见的人类病原体。本研究的主要目的是调查对碳青霉烯类抗生素耐药的肠杆菌科临床分离株中的碳青霉烯酶基因，并使用脉冲场凝胶电泳（PFGE）确定它们的克隆关系。
在本研究中，通过传统生化试验和API 20NE分离并鉴定细菌。采用纸片扩散法评估抗生素敏感性，使用E-test测定最低抑菌浓度（MIC）。采用改良 Hodge试验（MHT）进行碳青霉烯酶的表型测定。通过聚合酶链反应（PCR）扩增包括IMP、VIM、KPC、NDM和OXA-48在内的碳青霉烯酶基因。使用PFGE检查其克隆类型与1种限制酶之间的关系。
在40株对碳青霉烯类抗生素耐药或中度敏感的分离株中，29株（72.5%）菌株碳青霉烯酶表型呈阳性。此外，6株分离株含有包括IMP、VIM、NDM和OXA-48在内的碳青霉烯酶基因，但未在任何分离株中发现KPC基因。PFGE结果显示，我们地区的大肠杆菌菌株聚为8个脉冲型（A-H），克雷伯菌属分离株为5个脉冲型（A-E），变形杆菌属有2个脉冲型（A、B）。A、B和F脉冲型对抗菌药物的高耐药性归因于大肠杆菌临床分离株。
我们的结果可以反映医院医院感染中的一些多重耐药菌株。近年来，耐碳青霉烯分离株的广泛出现引起了越来越多的关注。因此，应设计并评估控制耐药菌株的具体策略。
