title: Emergence of linezolid-resistant coagulase-negative Staphylococcus in a cancer centre linked to increased linezolid utilization.
abstract: OBJECTIVE
  The prevalence of linezolid-resistant coagulase-negative Staphylococcus (CoNS) in the MD Anderson Cancer Center rose from 0.6% in 2007 to 5.5% in 2009. The aim of our study was to analyse the relationship between linezolid use and an outbreak of linezolid-resistant CoNS.
  
  
  METHODS
  We retrospectively identified 27 infection or colonization events. Eleven isolates were available for supplemental investigation; species identification, clonal relatedness and linezolid resistance mutation analysis. The medical records of the affected patients were reviewed and linezolid utilization data were obtained from the pharmacy.
  
  
  RESULTS
  Available isolates were confirmed as clonally related Staphylococcus epidermidis. Partial 23S rRNA gene sequencing found a G2576T mutation in all of the isolates tested. All patients received linezolid within 3 months prior to an event. Patients without a prior hospitalization had a longer time from admission to event; 29 versus 3.5 days (P = 0.002). The outbreak was preceded by a 51% increase in inpatient linezolid utilization and 64% of affected patients belonged to the leukaemia service, which had a utilization rate 3.1 times that of the other services (95% confidence interval: 2.96-3.23).
  
  
  CONCLUSIONS
  Increased linezolid utilization preceded the appearance of a linezolid-resistant CoNS clone. Patients probably acquired the clonal strain nosocomially, given the longer time from admission to event among patients with no previous admission to the MD Anderson Cancer Center. Linezolid administration then selected this strain, since all patients received linezolid prior to an event. A linezolid utilization rate of >or=13 defined daily doses/100 patient-days was similar to that reported in two other outbreaks and may be the threshold required to generate an outbreak.
authors.affiliation: Department of Infectious Diseases, Infection Control and Employee Health, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 1460, Houston, TX 77030, USA. vmulanov@mdanderson.org
authors.forename: Victor E
authors.initials: VE
authors.lastname: Mulanovich
authors.forename: Michael D
authors.initials: MD
authors.lastname: Huband
authors.forename: Sandra P
authors.initials: SP
authors.lastname: McCurdy
authors.forename: M Megan
authors.initials: MM
authors.lastname: Lemmon
authors.forename: Marykay
authors.initials: M
authors.lastname: Lescoe
authors.forename: Ying
authors.initials: Y
authors.lastname: Jiang
authors.forename: Kenneth V I
authors.initials: KV
authors.lastname: Rolston
authors.forename: P Rocco
authors.initials: PR
authors.lastname: LaSala
mesh_terms: D000081:Acetamides / Q000627:therapeutic use*; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D015373:Bacterial Typing Techniques; D016000:Cluster Analysis; D003030:Coagulase / Q000032:analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial; D004363:Drug Utilization / Q000706:statistics & numerical data*; D005838:Genotype; D006801:Humans; D000069349:Linezolid; D016522:Oncology Service, Hospital; D023303:Oxazolidinones / Q000627:therapeutic use*; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D012189:Retrospective Studies; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000201:enzymology / Q000302:isolation & purification; D014481:United States / Q000453:epidemiology
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D003030:Coagulase; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D023303:Oxazolidinones; D012338:RNA, Ribosomal, 23S; D000069349:Linezolid