Dissemination of the mcr-1 colistin resistance gene

Abstract

We read with interest the Article by Yi-Yun Liu and colleagues1Liu Y-Y Wang Y Walsh TR et al.Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study.Lancet Infect Dis. 2015; (published online Nov 18.)http://dx.doi.org/10.1016/S1473-3099(15)00424-7Google Scholar reporting the high rates of plasmid-mediated colistin resistance in Escherichia coli isolates from animal food sources in China. We share their concerns about potential widespread dissemination of the mcr-1 gene, which could lead to substantial morbidity and mortality associated with colistin failure in the clinical setting. The authors pointed out that identical genes were identified in E coli isolates sequenced by researchers in Malaysia, and thereby suggested that plasmid-mediated colistin resistance might already be present in southeast Asia. However, an identical gene is also present in a Salmonella enterica serotype Typhimurium isolate (GenBank accession number NZ_LFCC01000022) from a food sample in Portugal in 2011.2Figueiredo R Henriques A Sereno R Mendonça N da Silva GJ Antimicrobial resistance and extended-spectrum β-lactamases of Salmonella enterica serotypes isolated from livestock and processed food in Portugal: an update.Foodborne Pathog Dis. 2015; 12: 110-117Crossref PubMed Scopus (21) Google Scholar As meat products might include meat from several sources or be contaminated during processing, this discovery does not necessarily imply the presence of mcr-1-harbouring organisms in European farms. Nonetheless, the European population might have been exposed to mcr-1-harbouring organisms. Further analysis reinforced the significance of this finding. First, the mcr-1 gene is located on an IncHI2 plasmid in the S Typhimurium isolate, which differs from the IncI2-like plasmids in the E coli isolates from Asia. This finding shows that mcr-1 has horizontally transferred to other plasmid types, resulting in a potentially greater bacterial host range. Second, the nucleotide sequence of the S Typhimurium plasmid backbone is 99% identical to earlier salmonella plasmids identified in southern China (GenBank accession number KT334335 and KM877269), which suggests that the mcr-1-carrying plasmid in Salmonella S Typhimurium might have originated from China too. Third, the complete nucleotide sequence identity between mcr-1 in the S Typhimurium and E coli isolates suggests that the horizontal gene transfer was a recent event. This finding is highly alarming as it implies that dissemination to a geographically distant region has occurred in a short time. We believe that the mcr-1 gene is more mobile than suggested by Liu and colleagues, and has spread beyond Asia into Europe. We echo the call by Liu and colleagues, which has been substantiated by Paterson and Harris,3Paterson DL Harris PNA Colistin resistance: a major breach in our last line of defence.Lancet Infect Dis. 2015; (published online Nov 18.)http://dx.doi.org/10.1016/S1473-3099(15)00463-6Google Scholar to curtail the agricultural use of colistin, and emphasise the importance for a comprehensive strategic framework against antimicrobial resistance in China.4Cheng VCC Wong SCY Ho P-L Yuen K-Y Strategic measures for the control of surging antimicrobial resistance in Hong Kong and mainland of China.Emerg Microbes Infect. 2015; 4: e8Crossref PubMed Scopus (33) Google Scholar Additionally, specific strategies to mitigate the spread of antimicrobial resistance across geographical boundaries, such as judicious use of antibiotics in travellers,5Kantele A Laaveri T Mero S et al.Antimicrobials increase travelers' risk of colonization by extended-spectrum betalactamase-producing Enterobacteriaceae.Clinical Infect Dis. 2015; 60: 837-846Crossref PubMed Scopus (196) Google Scholar should be reinforced. We declare no competing interests. Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological studyThe emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance. Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasise the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria. Full-Text PDF