Azithromycin Resistance through Interspecific Acquisition of an Epistasis-Dependent Efflux Pump Component and Transcriptional Regulator in Neisseria gonorrhoeae.

Crista B Wadsworth,Yonatan H Grad,Brian J Arnold,Mohamad R Abdul Sater,Michael S Gilmore,William Shafer

doi:10.1128/mbio.01419-18

Crista B Wadsworth, Yonatan H Grad + Show 4 more

Open Access

https://doi.org/10.1128/mbio.01419-18

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Journal: mBio	Publication Date: Aug 7, 2018
Citations: 143	License type: CC BY 4.0

Affiliation: Harvard University, Brigham and Women's Hospital

Abstract

ABSTRACTMosaic interspecifically acquired alleles of the multiple transferable resistance (mtr) efflux pump operon correlate with increased resistance to azithromycin in Neisseria gonorrhoeae in epidemiological studies. However, whether and how these alleles cause resistance is unclear. Here, we use population genomics, transformations, and transcriptional analyses to dissect the relationship between variant mtr alleles and azithromycin resistance. We find that the locus encompassing the mtrR transcriptional repressor and the mtrCDE pump is a hot spot of interspecific recombination introducing alleles from Neisseria meningitidis and Neisseria lactamica into N. gonorrhoeae, with multiple rare haplotypes in linkage disequilibrium at mtrD and the mtr promoter region. Transformations demonstrate that resistance to azithromycin, as well as to other antimicrobial compounds such as polymyxin B and crystal violet, is mediated through epistasis between these two loci and that the full-length mosaic mtrD allele is required. Gene expression profiling reveals the mechanism of resistance in mosaics couples novel mtrD alleles with promoter mutations that increase expression of the pump. Overall, our results demonstrate that epistatic interactions at mtr gained from multiple neisserial species has contributed to increased gonococcal resistance to diverse antimicrobial agents.

Highlights

Mosaic interspecifically acquired alleles of the multiple transferable resistance efflux pump operon correlate with increased resistance to azithromycin in Neisseria gonorrhoeae in epidemiological studies
To gain insight into the evolutionary history of the mtrR transcriptional repressor and the mtrCDE pump, we analyzed patterns of diversity using the 1,102 Gonococcal Isolate Surveillance Project (GISP) isolates described by Grad et al [8, 34]
Linkage disequilibrium was strongest at mtrD and the mtr promoter region in a comparison of all pairs of single-nucleotide polymorphisms (SNPs) within mtrRCDE, with the highest linkage observed at pairs of variant sites within each of these loci (Fig. 1E and F; Table S1)

Summary

Introduction

Mosaic interspecifically acquired alleles of the multiple transferable resistance (mtr) efflux pump operon correlate with increased resistance to azithromycin in Neisseria gonorrhoeae in epidemiological studies. Extensive intragenus gene exchange has led to the concept of Neisseria as a consortium of species interconnected by allele sharing, with “fuzzy” borders permitting rapid access to new adaptive solutions [12, 13]. This produces genetic mosaicism within particular lineages, whereby some loci are the products of horizontal gene transfer and homologous recombination from other species. Aside from horizontal gene transfer facilitating the evolution of resistance to third-generation cephalosporins through acquisition of mosaic penA [8, 15], allelic exchange has not yet been demonstrated to be the basis for resistance to any other antibiotic class in this species

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