title: Susceptibility to tigecycline and linezolid among gram-positive isolates collected in the United States as part of the tigecycline evaluation and surveillance trial (TEST) between 2004 and 2009.
abstract: BACKGROUND
  The Tigecycline Evaluation and Surveillance Trial (TEST) was initiated in 2004 to chart the activity of tigecycline and comparator antimicrobial agents against gram-positive and gram-negative organisms globally.
  
  
  OBJECTIVE
  This study aimed to provide an analysis of the antimicrobial susceptibility of gram-positive organisms collected from the 9 census regions of the United States between 2004 and 2009.
  
  
  METHODS
  The MICs and antimicrobial susceptibility were determined using Clinical and Laboratory Standards Institute methodology. For tigecycline, US Food and Drug Administration susceptibility criteria were used.
  
  
  RESULTS
  A total of 8782 Staphylococcus aureus isolates (54.5% methicillin-resistant S aureus) were collected, with the highest percentage of MRSA isolates collected from the South Central region (67.9%). All S aureus isolates were susceptible to tigecycline, linezolid, and vancomycin. Overall, 4.6% of Enterococcus faecalis (n = 3753) and 69.1% of Enterococcus faecium (n = 1417) isolates were vancomycin resistant, with the highest rates in the East North Central region for E faecalis (7.1%) and the South Atlantic region for E faecium (79.5%). Small numbers of linezolid nonsusceptible E faecalis (n = 13) were identified. MIC(90) values for tigecycline were ≤0.25 mg/L against E faecalis and 0.12 mg/L against E faecium. Of the Streptococcus pneumoniae isolates collected (n = 4541), 1.1% were penicillin resistant. All S pneumoniae isolates were susceptible to linezolid and vancomycin; susceptibility to tigecycline varied between 80.9% (Pacific region) and 95.2% (West North Central region).
  
  
  CONCLUSIONS
  The rates of MRSA and vancomycin-resistant Enterococcus spp varied among the 9 census regions; however, susceptibility to linezolid, vancomycin, and tigecycline remained consistent, with low MIC(90) values and high rates of antimicrobial susceptibility.
authors.affiliation: Pfizer Inc, Collegeville, Pennsylvania 19426, USA. Michael.Dowzicky@pfizer.com
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dowzicky
mesh_terms: D000081:Acetamides / Q000627:therapeutic use*; D000890:Anti-Infective Agents / Q000627:therapeutic use*; D024901:Drug Resistance, Multiple, Bacterial; D013293:Enterococcus faecalis / Q000187:drug effects / Q000254:growth & development; D016984:Enterococcus faecium / Q000187:drug effects / Q000254:growth & development; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000254:growth & development; D016908:Gram-Positive Bacterial Infections / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D000069349:Linezolid; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D008826:Microbial Sensitivity Tests; D008911:Minocycline / Q000031:analogs & derivatives* / Q000627:therapeutic use; D023303:Oxazolidinones / Q000627:therapeutic use*; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000254:growth & development; D000078304:Tigecycline; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology; D020713:Vancomycin Resistance
chemical_list: D000081:Acetamides; D000890:Anti-Infective Agents; D023303:Oxazolidinones; D000078304:Tigecycline; D008911:Minocycline; D000069349:Linezolid