title: Polyphyletic emergence of linezolid-resistant staphylococci in the United States.
abstract: Since the year 2000, linezolid has been used in the United States to treat infections caused by antimicrobial-resistant Gram-positive cocci. At present, linezolid-resistant (Linr) Staphylococcus aureus and Staphylococcus epidermidis strains are rare and the diversity of their genetic backgrounds is unknown. We performed sequence-based strain typing and resistance gene characterization of 46 Linr isolates that were collected from local and national sources between the years 2004 and 2007. Resistance was found to occur in at least three clonal complexes (CCs; lineages) of S. aureus and in at least four subclusters of a predominant, phylogenetically unstable CC of S. epidermidis. New candidate resistance mutations in 23S rRNA and the L4 riboprotein were identified among the S. epidermidis isolates. These findings suggest that linezolid resistance has emerged independently in multiple clones of S. aureus and with a variety of ribosomal mutations in multiple clones of S. epidermidis.
authors.affiliation: Department of Microbiology and Immunology, New York Medical College, Valhalla, NY, USA.
authors.forename: Agnes
authors.initials: A
authors.lastname: Wong
authors.forename: Shilpa P
authors.initials: SP
authors.lastname: Reddy
authors.forename: Davida S
authors.initials: DS
authors.lastname: Smyth
authors.forename: Maria E
authors.initials: ME
authors.lastname: Aguero-Rosenfeld
authors.forename: George
authors.initials: G
authors.lastname: Sakoulas
authors.forename: D Ashley
authors.initials: DA
authors.lastname: Robinson
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D023303:Oxazolidinones / Q000494:pharmacology*; D010802:Phylogeny; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013203:Staphylococcal Infections / Q000382:microbiology; D013210:Staphylococcus / Q000145:classification / Q000187:drug effects* / Q000235:genetics*; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000235:genetics; D013212:Staphylococcus epidermidis / Q000145:classification / Q000187:drug effects / Q000235:genetics; D014481:United States
chemical_list: D000081:Acetamides; D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D023303:Oxazolidinones; D012338:RNA, Ribosomal, 23S; D012269:Ribosomal Proteins; C056368:ribosomal protein L4; D000069349:Linezolid