title: Linezolid-resistant clinical isolates of enterococci and Staphylococcus cohnii from a multicentre study in China: molecular epidemiology and resistance mechanisms.
abstract: Genetic characterisation of linezolid-resistant Gram-positive cocci in a multicentre study in China has not been reported previously. To study the mechanism underlying the resistance of linezolid-resistant isolates, nine Enterococcus faecalis, one Enterococcus faecium and three Staphylococcus cohnii isolates with various levels of resistance were collected from five hospitals across China in 2009-2012. The nine E. faecalis isolates were classified into seven sequence types, indicating that these linezolid-resistant E. faecalis isolates were polyclonal. Enterococci isolates had reduced susceptibility to linezolid (MICs of 4-8 mg/L) and had mutation of ribosomal protein L3, with three also having mutation of L4, but without the multidrug resistance gene cfr or the 23S rRNA mutation G2576T. The three S. cohnii isolates were highly resistant to linezolid (MICs of 64 mg/L to >256 mg/L), harboured the cfr gene and had the 23S rRNA mutation G2576T. Southern blotting indicated that the cfr gene of these three isolates resided on different plasmids (pHK01, pRM01 and pRA01). In plasmid pHK01, IS21-558 and the cfr gene were integrated into transposon Tn558. In plasmids pRM01 and pRA01, the cfr gene was flanked by two copies of an IS256-like insertion sequence, indicating that the transferable form of linezolid resistance is conferred by the cfr gene. In conclusion, the emergence of linezolid-resistant Gram-positive cocci in different regions of China is of concern. The cfr gene and the 23S rRNA mutation contribute to high-level linezolid resistance in S. cohnii, and the L3 and L4 mutations are associated with low-level linezolid resistance in enterococci.
authors.affiliation: Department of Clinical Laboratory, Peking University People's Hospital, Beijing 100044, People's Republic of China.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Chen
authors.forename: Weiyuan
authors.initials: W
authors.lastname: Wu
authors.forename: Ming
authors.initials: M
authors.lastname: Ni
authors.forename: Yingmei
authors.initials: Y
authors.lastname: Liu
authors.forename: Jixia
authors.initials: J
authors.lastname: Zhang
authors.forename: Fei
authors.initials: F
authors.lastname: Xia
authors.forename: Wenqiang
authors.initials: W
authors.lastname: He
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Zhanwei
authors.initials: Z
authors.lastname: Wang
authors.forename: Bin
authors.initials: B
authors.lastname: Cao
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D016000:Cluster Analysis; D004269:DNA, Bacterial / 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; D005260:Female; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology; D006761:Hospitals; D006801:Humans; D007223:Infant; D000069349:Linezolid; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D023303:Oxazolidinones / Q000494:pharmacology*; D010957:Plasmids; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D000090822:Ribosomal Protein L3; D012269:Ribosomal Proteins / Q000235:genetics; D013210:Staphylococcus / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D055815:Young Adult
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D023303:Oxazolidinones; D012338:RNA, Ribosomal, 23S; C000716547:RPL3 protein, human; D000090822:Ribosomal Protein L3; D012269:Ribosomal Proteins; D000069349:Linezolid
keywords: Enterococci; G2576T mutation; Linezolid resistance; Staphylococcus cohnii; cfr gene