Colistin-resistant Escherichia coli harbouring mcr-1 isolated from food animals in Hanoi, Vietnam

Abstract

In The Lancet Infectious Diseases, 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 Nov 18.)http://dx.doi.org/10.1016/S1473-3099(15)00424-7Google Scholar reported, for the first time, plasmid-mediated colistin resistance in Escherichia coli isolated from animals, food, and patients in China. We screened 24 extended-spectrum β-lactamase (ESBL, blaCTX-M) harbouring E coli isolated during 2014–15 from rectal swabs taken from chickens on two farms (n=11) in the Van Lam district of the Hung Yen province, and from a pig farm (seven) and a pig slaughterhouse (four) located in the Hoai Duc region of the Hanoi province, Vietnam. All strains were screened for the presence of mcr-1 using PCR and Sanger sequencing. The mcr-1 gene was detected in nine (37·5%) of 24 E coli strains, of which six were isolated from the rectal swabs of pigs on the farm, one from a rectal swab from a pig about to be slaughtered, and two strains from swabs collected from the lairage area of the slaughterhouse. All nine isolates had phenotypic colistin resistance (macrobroth dilution minimum inhibitory concentration of colistin was 4 mg/L or 8 mg/L). The mcr-1 sequence showed 100% sequence similarity to the gene reported in China.1Liu 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 Nov 18.)http://dx.doi.org/10.1016/S1473-3099(15)00424-7Google Scholar Plasmid sequencing (MiSeq, Illumina) from one mcr-1 positive strain isolated multiple genes encoding resistance to trimethoprim (dfrA12), tetracycline (tetA), aminoglycoside (aadA3, aph(3')-IA), phenicol (cmlA1), quinolone (qnrS1, oqxA), lincosamide (lnu(F)), and sulphonamide (sul2, sul3), and β-lactam (extended-spectrum β-lactamase blaCTX-M55) antibiotics. Blast comparison with the plasmid, pHNSHP45,1Liu 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 Nov 18.)http://dx.doi.org/10.1016/S1473-3099(15)00424-7Google Scholar showed 100% similarity in a 3677 bp region that included mcr-1 (1626 bp) and a complete ISApI1 mobile element including the transposase-encoding tnpA gene. Incompatibility typing using Plasmid Finder2Carattoli A Zankari E García-Fernández A et al.In silico detection and typing of plasmids using plasmidfinder and plasmid multilocus sequence typing.Antimicrob Agents and Chemother. 2014; 58: 3895-3903Crossref PubMed Scopus (2202) Google Scholar identified IncFII, IncF1A(H1), and IncF1B(K), and IncX1 replicons; however, none of these could be directly linked to the mcr-1 harbouring contig. Of note, the sequence coverage of the mcr-1 harbouring contig was roughly 100 times lower than the adjoining regions, indicating either carriage on a low-copy plasmid or a chromosomal origin of the gene. Next, we screened 112 ESBL-harbouring E coli isolated during 2014–15 from urine of outpatients and inpatients with symptomatic urinary tract infections collected at the National Pediatric, 103 General Military, and Cuba hospitals in Hanoi. mcr-1 was not detected in any of the urinary isolates. Our findings underline a high prevalence of the mcr-1 gene in ESBL-harbouring E coli isolated from rectal screenings of pigs in Vietnam; however, we did not find any evidence of transfer or emergence of the gene in ESBL-harbouring pathogenic E coli of human origin. These data add to recent studies showing a global emergence of the mcr-1 harbouring mobile genetic element linked to different plasmids,3Hasman H Hammerum A Hansen F et al.Detection of mcr-1 encoding plasmid-mediated colistin-resistant Escherichia coli isolates from human bloodstream infection and imported chicken meat, Denmark 2015.Euro Surveill. 2015; (published online Dec 10.)http://dx.doi.org/10.2807/1560-7917.ES.2015.20.49.30085PubMed Google Scholar underscoring the importance of active surveillance in both animal and human populations. BBX is supported by University of Antwerp Research Funds (BOF-DOCPRO 2012-27450). AJD is supported by European Union Horizon 2020 Research and Innovation Programme: Compare (collaborative management platform for detection and analyses of [re-]emerging and foodborne outbreaks in Europe: grant number 643476). The research done for this Correspondence was funded by the Flemish Inter-University Council (VLIR-UoS), TEAM/Own Initiatives-Programme 2013. 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