Co-carriage of the oxazolidinone resistance genes cfr and optrA in a linezolid-resistant Staphylococcus rostri isolate from a pig-farm worker

This is the authors' abstract. We don't add key points for this paper.

Since the first report of the cfr gene, which encodes an rRNA methyltransferase, in a bovine isolate of Staphylococcus sciuri in 2000,1 sporadic occurrences of linezolid-resistant Enterococcus2 and Staphylococcus spp.1,3 carrying cfr-positive plasmids have been found in isolates of both human and animal origin. Tedizolid, a second-generation oxazolidinone, approved by the FDA in 2014, exhibits improved antimicrobial activity against cfr-mediated linezolid resistance. Soon after its release, a novel oxazolidinone and phenicol resistance gene, optrA, was frequently identified in enterococci originating from food-producing animals and humans.4 The optrA gene encodes an ATP-binding cassette transporter (ABC-F) protein that confers resistance to oxazolidinones (linezolid and tedizolid) and phenicols (florfenicol and chloramphenicol). Recently, optrA was identified in porcine-associated non-aureus staphylococci (NAS) including S. sciuri.5 Even more alarming, coexistence of cfr and optrA has been reported in pig-associated S. sciuri isolates5 and in a clinical Enterococcus faecalis isolate.2 In this study, a total of 445 staphylococcal isolates (81 S. aureus and 364 NAS isolates), which were collected from previous studies from our laboratory between 2017 and 2018,3,6 were screened for the presence of optrA (optrA-F: 5′-AACGCAAAGGAGGATATGAAAA-3′ and optrA-R: 5′-TCAAGGTGGTTAGTAGGTTCATCA-3′) and cfr using specific primer sets as previously described.3 Through the screening, one linezolid-resistant S. rostri SR13 isolate recovered from a nasal swab sample of a pig-farm worker in Jeolla, Korea, was identified as positive for cfr and optrA genes.