Whole-genome sequencing of Enterococcus hirae CQP3-9, a strain carrying the phenicol-oxazolidinone-tetracycline resistance gene poxtA of swine origin in China.

Objectives: The aim of this study was to characterise the whole genome sequence of linezolid-intermediate Enterococcus hirae strain CQP3-9 isolated from a large-scale swine farm in Sichuan Province, China, in August 2018.

Methods: An Illumina MiSeq platform (400-bp paired-end reads with 230-fold average coverage) and PacBio RS II sequencing instrument (100-fold average read depth) were used for genome sequencing. The chromosome and two plasmids were assembled using the software SMRT portal v.3.2.0. Acquired antimicrobial resistance genes were identified using ResFinder 3.1.

Results: The genome of E. hirae strain CQP3-9 consists of one 2 695 881-bp chromosome, one 125 915-bp plasmid (pCQP3-9_1) and one 33 132-bp plasmid (pCQP3-9_2). The genome of CQP3-9 contains 2458 coding sequences and 89 RNA genes. The poxtA gene is the only linezolid resistance gene in CQP3-9, located on plasmid pCQP3-9_2 that co-harbours erm(B) (macrolide resistance), fexB (chloramphenicol and florfenicol resistance), and tet(M) and tet(L) (tetracycline resistance).

Conclusion: Here we report for the first time the phenicol-oxazolidinone-tetracycline resistance gene poxtA in E. hirae, located on a plasmid that co-harbours erm(B), fexB, tet(L) and tet(M). The genome sequence of E. hirae CQP3-9 provides valuable information for the dissemination of poxtA among enterococci.