Detection of the Novel optrA Gene Among Linezolid-Resistant Enterococci in Barcelona, Spain Jordi Ca ` mara, 1 Mariana Camoez, 1,2 Fe Tubau, 1,3 Miquel Pujol, 2,4 Josefina Ayats, 1,3 Carmen Ardanuy, 1,3 and M. A ´ ngeles Domı ´nguez 1,2 The purpose of this study was to describe the presence of the novel optrA gene among clinical isolates of enterococci in a Spanish teaching hospital (May 2016–April 2017). optrA and cfr genes were screened by PCR in all isolates showing linezolid minimal inhibitory concentration (MIC) ‡4 mg/L. The genetic relatedness of the isolates, the presence of resistance and virulence genes, and the genetic environment of optrA were assessed by whole-genome sequencing (WGS). Six of 1,640 enterococci had linezolid MIC ‡4 mg/L. Among them, the optrA gene was detected in five Enterococcus faecalis isolated from unrelated patients. Although none of them had received linezolid or chloramphenicol, all had antecedents of recent quinolone consumption. WGS analysis revealed the existence of two different genotypes: ST585 and ST474. cfr was not detected in any of the isolates. No mutations were detected among the 23S ribosomal RNA and the ribosomal proteins L3, L4, and L22. Both genotypes also carried genes related to aminoglycoside, lincosamide, macrolide, phenicol, and tetracycline resistance. Detection of optrA in a setting with low linezolid consumption and among patients without ante- cedents of oxazolidinone therapy is of concern. Keywords: linezolid, optrA, cfr, enterococci, chloramphenicol, Enterococcus faecalis Introduction L inezolid resistance is emerging as a problem in the treatment of multidrug-resistant Gram-positive organ- isms, particularly methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium. 1,2 Among enterococci, linezolid resistance is mainly mediated by chro- mosomal mutations in domain V of the 23S ribosomal RNA (rRNA). 3 However, a transferable oxazolidinone resistance gene (cfr), which encodes a methyltransferase that modifies the 23S rRNA, was described in 2001. 4 This gene confers resistance to linezolid, phenicols, lincosamides, pleuromutilins, and streptogramin A. Recently, a novel mechanism (optrA) was described in Enterococcus spp., 5–12 Staphylococcus sciuri, 13,14 and Streptococcus suis, 15 indicating its ability to spread to different genus. optrA encodes an ABC-F protein that pro- tects the bacterial ribosome from the antibiotic inhibition, has the ability to spread through plasmids, and confers re- sistance to linezolid and phenicols. 5,16 In our setting, Hospital Universitari de Bellvitge (HUB), linezolid resistance is rare (<1% in both enterococci and staphylococci) and the cfr gene has been sporadically de- tected in S. aureus. 17 The purpose of this study was to screen for the presence of transferable linezolid resistance among linezolid-resistant clinical isolates of enterococci in a tertiary care hospital in Barcelona, Spain. Materials and Methods Study setting, bacterial isolates, and antimicrobial susceptibility testing This study was performed at HUB, a 700-bed teaching hospital located in the urban area of Barcelona, Spain. From May 2016 to April 2017, all enterococci isolates obtained from clinical samples were routinely identified by Matrix- Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) (Bruker Daltonik GmbH, Bremen, Germany) and tested for antimicrobial susceptibility by microdilution (Microscan Ò ; Beckman Coulter, Brea, CA) following the Clinical and Laboratory Standards Institute (CLSI) recommendations and criteria. 18 The linezolid minimal inhibitory concentration (MIC) breakpoints were as follows: 1 Microbiology Department, Hospital Universitari de Bellvitge-Universitat de Barcelona-IDIBELL, L’Hospitalet de Llobregat, Barce- lona, Spain. 2 Spanish Network for Research in Infectious Diseases (REIPI), Instituto de Salud Carlos III, Madrid, Spain. 3 CIBER de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, Madrid, Spain. 4 Infectious Diseases Department, Hospital Universitari de Bellvitge-Universitat de Barcelona-IDIBELL, L’Hospitalet de Llobregat, Barcelona, Spain. MICROBIAL DRUG RESISTANCE Volume 00, Number 00, 2018 ª Mary Ann Liebert, Inc. DOI: 10.1089/mdr.2018.0028 1 Downloaded by 83.35.26.9 from www.liebertpub.com at 09/12/18. For personal use only.