| Summary: | This study was performed to investigate the presence and characteristics of the oxazolidinone resistance genes <i>optrA</i> and <i>cfr</i>(D) in <i>Streptococcus parasuis</i>. In total, 36 <i>Streptococcus</i> isolates (30 <i>Streptococcus suis</i> isolates, 6 <i>Streptococcus parasuis</i> isolates) were collected from pig farms in China in 2020–2021, using PCR to determine the presence of <i>optrA</i> and <i>cfr</i>. Then, 2 of the 36 Streptococcus isolates were further processed as follows. Whole-genome sequencing and de novo assembly were employed to analyze the genetic environment of the <i>optrA</i> and <i>cfr</i>(D) genes. Conjugation and inverse PCR were employed to verify the transferability of <i>optrA</i> and <i>cfr</i>(D). The <i>optrA</i> and <i>cfr</i>(D) genes were identified in two <i>S. parasuis</i> strains named SS17 and SS20, respectively. The <i>optrA</i> of the two isolates was located on chromosomes invariably associated with the <i>araC</i> gene and Tn<i>554</i>, which carry the resistance genes <i>erm</i>(A) and <i>ant</i>(9). The two plasmids that carry <i>cfr</i>(D), pSS17 (7550 bp) and pSS20-1 (7550 bp) have 100% nucleotide sequence identity. The <i>cfr</i>(D) was flanked by GMP synthase and IS1202. The findings of this study extend the current knowledge of the genetic background of <i>optrA</i> and <i>cfr</i>(D) and indicate that Tn<i>554</i> and IS1202 may play an important role in the transmission of <i>optrA</i> and <i>cfr</i>(D), respectively.
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