AUTHOR=Du Fanshu , Lv Xi , Duan Duan , Wang Liping , Huang Jinhu 

TITLE=Characterization of a Linezolid- and Vancomycin-Resistant Streptococcus suis Isolate That Harbors optrA and vanG Operons

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02026

DOI=10.3389/fmicb.2019.02026

ISSN=1664-302X

ABSTRACT=<p>Linezolid and vancomycin are among the last-resort antimicrobial agents in the treatment of multidrug-resistant Gram-positive bacterial infections. Linezolid- and vancomycin-resistant (LVR) Gram-positive bacteria may pose severe threats to public health. In this study, three <italic>optrA-</italic> and <italic>vanG</italic>-positive <italic>Streptococcus suis</italic> strains were isolated from two farms of different cities. There were only 1 and 343 single-nucleotide polymorphisms in coding region (cSNPs) of HCB4 and YSJ7 to YSJ17, respectively. Mobilome analysis revealed the presence of <italic>vanG</italic>, <italic>erm</italic>(B), <italic>tet</italic>(O/W/32/O), and <italic>aadE</italic>-<italic>apt</italic>-<italic>sat4</italic>-<italic>aphA3</italic> cluster on an integrative and conjugative element, ICE<italic>Ssu</italic>YSJ17, and <italic>erm</italic>(B), <italic>aphA3</italic>, <italic>aac(6′)-aph(2″)</italic>, <italic>cat</italic>pC<sub>194</sub>, and <italic>optrA</italic> on a prophage, ΦSsuYSJ17-3. ICE<italic>Ssu</italic>YSJ17 exhibited a mosaic structure and belongs to a highly prevalent and transferable ICE<italic>Sa</italic>2603 family of <italic>Streptococcus</italic> species. ΦSsuYSJ17-3 shared conserved backbone to a transferable prophage Φm46.1. A novel composite transposon, IS<italic>1216E</italic>-<italic>araC</italic>-<italic>optrA</italic>-<italic>hp</italic>-<italic>cat</italic>pC<sub>194</sub>-IS<italic>1216E</italic>, which can be circulated as translocatable unit (TU) by IS<italic>1216E</italic>, was integrated on ΦSsuYSJ17-3. Vancomycin resistance phenotype and <italic>vanG</italic> transcription assays revealed that the <italic>vanG</italic> operon was inducible. The LVR strain YSJ17 exhibited moderate virulence in a zebrafish infection model. To our knowledge, this is the first report of LVR isolate, which is mediated by acquired resistance genes <italic>optrA</italic> and <italic>vanG</italic> operons in Gram-positive bacteria. Since <italic>S. suis</italic> has been recognized as an antimicrobial resistance reservoir in the spread of resistance genes to major streptococcal pathogens, the potential risks of disseminating of <italic>optrA</italic> and <italic>vanG</italic> from <italic>S. suis</italic> to other <italic>Streptococcus</italic> spp. are worrisome and routine surveillance should be strengthened.</p>