Abstract
Macrolide-resistant Streptococcus suis is highly prevalent worldwide. The acquisition of the erm(B) gene mediated by mobile genetic elements (MGEs) in particular integrative and conjugative elements (ICEs) is recognized as the main reason for the rapid spread of macrolide-resistant streptococcal strains. However, knowledge about different erm(B)-carrying elements responsible for the widespread of macrolide resistance and their transferability in S. suis remains poorly understood. In the present study, two erm(B)- and tet(O)-harboring putative ICEs, designated as ICESsuYSB17_rplL and ICESsuYSJ15_rplL, and a novel erm(B)- and aadE-spw-like-carrying genomic island (GI), named GISsuJHJ17_rpsI, were identified to be excised from the chromosome and transferred among S. suis strains with different serotypes. ICESsuYSB17_rplL and ICESsuYSJ15_rplL were integrated downstream the rplL gene, a conserve locus of the ICESa2603 family. GISsuJHJ17_rpsI, with no genes belonging to the conjugation module, was integrated into the site of rpsI. All transconjugants did not exhibit obvious fitness cost by growth curve and competition assays when compared with the recipient. The results demonstrate that different erm(B)-carrying elements were presented and highlight the role of these elements in the dissemination of macrolide resistance in S. suis.
Highlights
The rapid increase of macrolide resistance in Streptococcus has been reported worldwide from both pig and human isolates during the past two decades (Princivalli et al, 2009; Palmieri et al, 2011; Vela et al, 2017)
Recent studies have demonstrated that the erm(B) and tet(O) genes co-existed on different integrative and conjugative elements (ICEs) in S. suis isolates of both pig and human origins (Holden et al, 2009; Zhang et al, 2011; Huang et al, 2016a,c)
We identified three erm(B)-carrying transferable elements, including two erm(B)- and tet(O)-harboring putative ICEs, belonging to the ICESa2603 family, and a novel erm(B)-carrying genomic island (GI), which can be horizontally transferred among S. suis strains with different serotypes
Summary
The rapid increase of macrolide resistance in Streptococcus has been reported worldwide from both pig and human isolates during the past two decades (Princivalli et al, 2009; Palmieri et al, 2011; Vela et al, 2017). Different erm(B)-Carrying Elements in S. suis and active efflux by the mef and msr genes (Wilson, 2014; Fyfe et al, 2016) These resistance genes are frequently carried by mobile genetic elements (MGEs), such as plasmids, transposons, prophages, and more recently, integrative and conjugative elements (ICEs) (Horaud et al, 1985; Woodbury et al, 2008; Varaldo et al, 2009; Huang et al, 2016b,c; Feßler et al, 2018; Libante et al, 2019). S. suis is a key antibiotic resistance gene reservoir and a major zoonotic pathogen responsible for severe economic loss to the swine industry This bacterium causes specific diseases in humans after contact with infected animals or derived food products. We identified three erm(B)-carrying transferable elements, including two erm(B)- and tet(O)-harboring putative ICEs, belonging to the ICESa2603 family, and a novel erm(B)-carrying GI, which can be horizontally transferred among S. suis strains with different serotypes
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