Distribution of optrA and cfr in florfenicol-resistant Staphylococcus sciuri of pig origin

A novel transferable oxazolidinone-phenicol resistance gene, optrA, which confers resistance to linezolid, the next-generation oxazolidinone tedizolid, and also to chloramphenicol and florfenicol, has been identified in enterococcal and staphylococcal species. Here, we investigated the epidemiology of optrA in florfenicol-resistant Staphylococcus spp. isolates of pig origin, and characterized the genetic context of oxazolidinone resistance genes in 20 optrA-positive florfenicol- and methicillin-resistant S. sciuri isolates, 11 (55%) of which also harbored the multi-resistance gene cfr. Pulsed-field gel electrophoresis and direct repeat unit (dru) typing of the 20 optrA-positive S. sciuri isolates revealed 17 patterns and four distinct dru types, respectively. Nine and six different arrangements of the optrA and cfr gene regions, respectively, were identified among the isolates. The arrangements optrA-araC-Tn558 or optrA-ATn558 were present in all optrA-positive isolates, and in three of them, ISEnfa5 and cfr were located immediately downstream of optrA. The cfr-carrying segment in eight isolates was similar to the corresponding region of the staphylococcal plasmid pWo28-3, in which the coexistence of cfr and optrA was identified for the first time.