摘要

碳青霉烯类药物的失效导致最后一种药物粘杆菌素的使用增加，可能导致肠杆菌科细菌对粘杆菌素耐药性的发展和扩散。大肠菌素属于多粘菌素（阳离子多肽）家族，对革兰氏阴性菌具有广谱活性。在这项研究中，我们从德里的污水中获得了253个非重复细菌分离株，并从表型上筛选了大肠菌素抗性。在47株阳性菌株中，在5株菌株中检测到了大肠菌素抗性基因mcr-1。基于基于16S核糖体RNA的鉴定，细菌分离物被发现为大肠杆菌，维罗纳气单胞菌和达克气单胞菌。在所有五个mcr-1阳性分离株中均检测到抗扩谱β-内酰胺酶（ESBL）的决定簇CTX-M和TEM。根据文献调查，这是世界范围内Veronii aeromonas and dhakensis aeromonas dhakensis mcr-1基因的首次报道。此外，印度的污水中尚未早期报道mcr-1基因。所有五种分离物针对9种不同类别药物的抗生素敏感性测试均显示具有较高的最低抑菌浓度值的多药耐药表型。体外转结合研究显示成功转移了mcr-1和其他抗ESBL的决定簇。基于质粒的mcr-1基因在环境中产生的大肠菌素抗性表型的出现以及越来越多的细菌分离株令人关注。需要对不同水体进行全面调查并进行流行病学研究，以评估传播耐药性决定因素的风险。

Increased use of colistin, a last resort drug due to failure of carbapenems, has possibly contributed in development and spread of resistance to colistin among Enterobacteriaceae. The colistin belongs to the family of polymyxins, cationic polypeptides, with broad-spectrum activity against Gram-negative bacteria. In this study, we obtained 253 non-duplicate bacterial isolates from sewage water in Delhi and phenotypically screened for colistin resistance. Of the 47 positive isolates, the colistin resistance gene mcr-1 was detected among 5 isolates. Based on 16S ribosomal RNA-based identification, bacterial isolates were found to be Escherichia coli, Aeromonas veronii, and Aeromonas dhakensis. Extended spectrum β-lactamases (ESBL)-resistant determinants CTX-M and TEM were detected in all five mcr-1 positive isolates. On the basis of literature survey, this is the first report of mcr-1 gene from Aeromonas veronii and Aeromonas dhakensis worldwide. Furthermore, mcr-1 gene has not been reported earlier from sewage water in India. Antibiotic susceptibility test of all five isolates against 9 different classes of drugs revealed multidrug-resistant phenotype with high minimum inhibitory concentration values. In vitro transconjugation studies showed successful transfer of mcr-1 and other ESBL-resistant determinants. The occurrence of colistin resistance phenotype conferred by plasmid-based mcr-1 gene in the environment and an ever-increasing list of bacterial isolates is a cause of concern. A comprehensive survey of different water bodies and epidemiological studies are required to assess the risk of dissemination of resistance determinants.

https://www.ncbi.nlm.nih.gov/pubmed/31625114