Ovejero C M, Delgado-Blas J F, Calero-Caceres W, Muniesa M, Gonzalez-Zorn B
Department of Animal Health and VISAVET, Universidad Complutense de Madrid, Madrid, Spain.
Department of Microbiology, Universitat de Barcelona, Barcelona, Spain.
J Antimicrob Chemother. 2017 Apr 1;72(4):1050-1053. doi: 10.1093/jac/dkw533.
The mobile colistin resistance gene mcr-1 has been identified worldwide in human and animal sources, while its occurrence in the environment is still largely unknown. The aim of this study was to investigate the presence of mcr-1 -harbouring Enterobacteriaceae in water samples obtained from rivers and waste water treatment plants in the area of Barcelona, Spain.
The presence of mcr-1 was detected by PCR. Bacterial identification was performed via MALDI-TOF MS. Resistance to colistin was determined by a broth dilution method. The epidemiological relationship between the positive isolates was assessed with PFGE and ST was determined by MLST. Plasmid characterization was performed by transformation experiments, antimicrobial susceptibility testing and incompatibility group PCR.
Thirty MDR isolates bearing mcr-1 , 29 Escherichia coli (ST632 and ST479) and 1 Klebsiella pneumoniae (ST526), were identified in sewage from two different waste water treatment plants, whereas the gene was not found in river water. All isolates, including the K. pneumoniae , harboured bla CTX-M-55 and bla TEM-1 . mcr-1 was in all cases associated with an IncI2 plasmid, which only conferred resistance to colistin. mcr-1 was harboured by two predominant E. coli clones that were found in both waste water treatment plants.
This study showed a high occurrence of mcr-1 in the sewage of Barcelona, mainly due to the dissemination of two E. coli pulsotypes that are circulating in the population. The presence of mcr-1 in the environment is a cause for concern, and suggests high prevalence of mcr-1 in the community.
移动性黏菌素耐药基因mcr - 1已在全球范围内的人类和动物源中被鉴定出来，但其在环境中的出现情况仍 largely未知。本研究的目的是调查从西班牙巴塞罗那地区的河流和污水处理厂采集的水样中携带mcr - 1的肠杆菌科细菌的存在情况。
通过PCR检测mcr - 1的存在。通过基质辅助激光解吸电离飞行时间质谱（MALDI - TOF MS）进行细菌鉴定。采用肉汤稀释法测定对黏菌素的耐药性。用脉冲场凝胶电泳（PFGE）评估阳性分离株之间的流行病学关系，通过多位点序列分型（MLST）确定序列类型（ST）。通过转化实验、抗菌药物敏感性测试和不相容群PCR进行质粒特征分析。
在两个不同污水处理厂的污水中鉴定出30株携带mcr - 1的多重耐药分离株，其中29株为大肠杆菌（ST632和ST479），1株为肺炎克雷伯菌（ST526），而在河水中未发现该基因。所有分离株，包括肺炎克雷伯菌，都携带blaCTX - M - 55和blaTEM - 1。在所有情况下，mcr - 1都与一个IncI2质粒相关联，该质粒仅赋予对黏菌素的耐药性。mcr - 1由在两个污水处理厂均发现的两个主要大肠杆菌克隆携带。
本研究表明巴塞罗那污水中mcr - 1的出现率很高，主要是由于两种在人群中传播的大肠杆菌脉冲型的扩散。环境中mcr - 1的存在令人担忧，并表明该基因在社区中具有很高的流行率。
