title: Linezolid-resistant enterococci in Polish hospitals: species, clonality and determinants of linezolid resistance.
abstract: The significant increase of the linezolid-resistant enterococci (LRE) has been observed in Polish hospitals since 2012 and our study aimed at elucidating the possible reasons for this phenomenon. Polish LRE isolates were analysed by multilocus-sequence typing (MLST) and multiple locus variable-number tandem repeat (VNTR) analysis (MLVA), polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP) to establish clonal relatedness and mechanism of linezolid resistance, respectively. Fifty analysed LRE (2008-2015) included mostly Enterococcus faecium (82%) and Enterococcus faecalis (16%). Enterococcus faecium belonged to the hospital-adapted lineages 17/18 and 78, while E. faecalis isolates represented ST6, a hospital-associated type, and ST116, found in both humans and food-production animals. The G2576T 23S rRNA mutation was the most frequent (94%) mechanism of linezolid/tedizolid resistance of LRE. None of the isolates carried the plasmid-associated gene of Cfr methyltransferase, whereas optrA, encoding the ABC-type drug transporter, was identified in two E. faecalis isolates. In these isolates, optrA was located on a plasmid, transferable to both E. faecium and E. faecalis, whose partial (36.3 kb) sequence was 100% identical to the pE394 plasmid, identified previously in China in both clinical and farm animal isolates. The optrA-E. faecium transconjugant displayed a significant growth deficiency, in contrast to the optrA-E. faecalis. Our study indicates the role of mutation acquisition by hospital-adapted clones of enterococci as a major driver of increasing resistance to linezolid and tedizolid. Transferability and apparent lack of a biological cost of resistance suggest that E. faecalis may be a natural reservoir of optrA, an emerging mechanism of oxazolidinone resistance.
authors.affiliation: Department of Molecular Microbiology, National Medicines Institute, Chełmska 30/34, 00-725, Warsaw, Poland.
authors.forename: I
authors.initials: I
authors.lastname: Gawryszewska
authors.affiliation: Department of Epidemiology and Clinical Microbiology, National Medicines Institute, Chełmska 30/34, 00-725, Warsaw, Poland.
authors.forename: D
authors.initials: D
authors.lastname: Żabicka
authors.affiliation: Department of Epidemiology and Clinical Microbiology, National Medicines Institute, Chełmska 30/34, 00-725, Warsaw, Poland.
authors.forename: W
authors.initials: W
authors.lastname: Hryniewicz
authors.affiliation: Department of Molecular Microbiology, National Medicines Institute, Chełmska 30/34, 00-725, Warsaw, Poland. ewasadowy@cls.edu.pl.
authors.forename: E
authors.initials: E
authors.lastname: Sadowy
mesh_terms: D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D013293:Enterococcus faecalis / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D016984:Enterococcus faecium / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D022761:Gene Transfer, Horizontal; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology*; D006761:Hospitals; D006801:Humans; D000069349:Linezolid / Q000494:pharmacology*; D026901:Membrane Transport Proteins / Q000235:genetics; D018598:Minisatellite Repeats; D058885:Multilocus Sequence Typing; D009154:Mutation; D010957:Plasmids / Q000032:analysis; D011044:Poland / Q000453:epidemiology; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012338:RNA, Ribosomal, 23S / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D026901:Membrane Transport Proteins; D012338:RNA, Ribosomal, 23S; D000069349:Linezolid