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Inducible colistin resistance via a disrupted plasmid-borne mcr-1 gene in a 2008 Vietnamese Shigella sonnei isolate.

ABSTRACT: The objective of this study was to assess the presence of mcr-1 in Shigella sonnei isolated in Vietnam.WGS data were analysed for the presence of the mcr-1 gene sequence. The association of mcr-1 with a plasmid was assessed by PCR and by conjugation.Through genome sequencing we identified a plasmid-associated inactive form of mcr-1 in a 2008 Vietnamese isolate of Shigella sonnei. The plasmid was conjugated into Escherichia coli and mcr-1 was activated upon exposure to colistin, resulting in highly colistin-resistant transconjugants.This is the first description of the mcr-1 gene in Shigella, which is atypical given that colistin is not ordinarily used to treat diarrhoea. Our data suggest the mcr-1 gene has been circulating in human-restricted pathogens for some time but likely carries a selective fitness cost.

SUBMITTER: Pham Thanh D

PROVIDER: S-EPMC4954929 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Inducible colistin resistance via a disrupted plasmid-borne mcr-1 gene in a 2008 Vietnamese Shigella sonnei isolate.

Pham Thanh Duy D Thanh Tuyen Ha H Nguyen Thi Nguyen To T Chung The Hao H Wick Ryan R RR Thwaites Guy E GE Baker Stephen S Holt Kathryn E KE

The Journal of antimicrobial chemotherapy 20160530 8

<h4>Objectives</h4>The objective of this study was to assess the presence of mcr-1 in Shigella sonnei isolated in Vietnam.<h4>Methods</h4>WGS data were analysed for the presence of the mcr-1 gene sequence. The association of mcr-1 with a plasmid was assessed by PCR and by conjugation.<h4>Results</h4>Through genome sequencing we identified a plasmid-associated inactive form of mcr-1 in a 2008 Vietnamese isolate of Shigella sonnei. The plasmid was conjugated into Escherichia coli and mcr-1 was act ...[more]

PMID: 27246235

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Project description:The most common mechanism of trimethoprim (TMP)-resistance is the acquisition of dihydrofolate reductase enzyme resistant to this drug. Previous molecular characterization of TMP-genes resistance in Chilean isolates of Shigella sonnei searching for dfrA1 and dfrA8, showed solely the presence of dfrA8 (formerly dhfrIIIc). However, these genetic markers were absent in S. sonnei strains further isolated during an outbreak in 2009. To identify the TMP-resistance gene in these strains, a genomic DNA library from a TMP-resistant (TMP(R)) S. sonnei representative strain for the outbreak was used to clone, select and identify a TMP-resistance marker. The TMP(R) clone was sequenced by primer walking, identifying the presence of the dfrA14 gene in the sul2-strA'-dfrA14-'strA-strB gene arrangement, harbored in a native 6779-bp plasmid. The same plasmid was isolated by transforming with a ~4.2 MDa plasmid extracted from several TMP(R) S. sonnei strains into Escherichia coli. This plasmid, named pABC-3, was present only in dfrA14-positive strains and was homologous to a previously described pCERC-1, but different due to the absence of an 11-bp repetitive unit. The distribution of dfrA1, dfrA8, and dfrA14 TMP-resistance genes was determined in 126 TMP(R) S. sonnei isolates. Most of the strains (96%) carried only one of the three TMP-resistance genes assessed. Thus, all strains obtained during the 2009-outbreak harbored only dfrA14, whereas, dfrA8 was the most abundant gene marker before outbreak and, after the outbreak dfrA1 seems have appeared in circulating strains. According to PFGE, dfrA14-positive strains were clustered in a genetically related group including some dfrA1- and dfrA8-positive strains; meanwhile other genetic group included most of the dfrA8-positive strains. This distribution also correlated with the isolation period, showing a dynamics of trimethoprim genetic markers prevalent in Chilean S. sonnei strains. To our knowledge, dfrA14 gene associated to a small non-conjugative plasmid was detected for the first time in Shigella. Apparently, the strain causing the outbreak must have been introduced, changing drastically the genetic distribution of trimethoprim resistance in Chilean S. sonnei strains.

Dataset Information

Inducible colistin resistance via a disrupted plasmid-borne mcr-1 gene in a 2008 Vietnamese Shigella sonnei isolate.

Publications

Inducible colistin resistance via a disrupted plasmid-borne mcr-1 gene in a 2008 Vietnamese Shigella sonnei isolate.

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