AUTHOR=Hadjadj Linda , Baron Sophie Alexandra , Olaitan Abiola Olumuyiwa , Morand Serge , Rolain Jean-Marc 

TITLE=Co-occurrence of Variants of mcr-3 and mcr-8 Genes in a Klebsiella pneumoniae Isolate From Laos

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02720

DOI=10.3389/fmicb.2019.02720

ISSN=1664-302X

ABSTRACT=<p>Colistin is considered as a last resort antibiotic. The re-use of this antibiotic highlighted the emergence of colistin resistance mediated by chromosomal and plasmidic resistance mechanisms. Five colistin-resistant <italic>Klebsiella pneumoniae</italic> strains from Laos and Thailand were analyzed by Next Generation Sequencing (NGS) approaches to determine their colistin resistance mechanisms. Antimicrobial susceptibility testing, conjugation and transformation were performed on these strains. Moreover, whole genome sequencing (WGS) combining Illumina (MiSeq) and Oxford Nanopore technologies (MinION) was realized to obtain closed genomes and plasmids. Resistome analyses as well as location of <italic>mcr</italic> genes and its genetic environments were done <italic>in silico</italic>. All five strains had colistin MIC of 32 mg/L and were positive for <italic>mcr-3</italic> variants including additionally positive for a <italic>mcr-8</italic> variant gene. The novel variants were named <italic>mcr</italic>-<italic>3.21</italic>, <italic>mcr</italic>-<italic>3.26, mcr</italic>-<italic>3.28</italic>, and <italic>mcr-8.3</italic> genes. The <italic>mcr-3</italic> variants genes were located on plasmids IncP1, IncFII, and IncI1 type, while <italic>mcr-8.3</italic> gene was found on an IncFII type plasmid. The genetic environment of <italic>mcr</italic>-<italic>3.21</italic> and <italic>mcr-3.26</italic> genes were composed of a composite transposon IS<italic>Kpn40</italic>- <italic>mcr</italic>-<italic>3</italic>-dgkA- IS<italic>Kpn40.</italic> Concerning <italic>mcr-8.3</italic> gene, a similar genetic environment of <italic>mcr</italic>-<italic>8.1</italic> gene surrounded by ISIX<italic>2</italic> and IS<italic>903B</italic> was observed. To the best of our knowledge, this is the first description of the novel variants <italic>mcr</italic>-<italic>3.21</italic>, <italic>mcr</italic>-<italic>3.26, mcr-3.28</italic> and <italic>mcr</italic>-<italic>8.3</italic> genes as well as the first study on co-occurrence of <italic>mcr</italic>-<italic>3</italic> and <italic>mcr-8</italic> genes. Spread and evolution of <italic>mcr</italic> genes should be monitored.</p>