title: An investigation of vancomycin minimum inhibitory concentration creep among methicillin-resistant Staphylococcus aureus strains isolated from pediatric patients and healthy children in Northern Taiwan.
abstract: OBJECTIVE
  The phenomenon of vancomycin minimum inhibitory concentration (MIC) creep is an increasingly serious problem in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. In this study, we investigated the vancomycin and daptomycin MIC values of MRSA strains isolated from pediatric patients and MRSA colonized healthy children. Then, we assessed whether there was evidence of clonal dissemination for strains with an MIC to vancomycin of ≥ 1.5 μg/mL.
  
  
  METHODS
  We collected clinical MRSA isolates from pediatric patients and from healthy children colonized with MRSA during 2008-2012 at a tertiary medical center in northern Taiwan and obtained vancomycin and daptomycin MIC values using the Etest method. Pulse-field gel electrophoresis (PFGE) and staphylococcal cassette chromosome (SCCmec) typing were used to assess clonal dissemination for strains with an MIC to vancomycin of ≥ 1.5 μg/mL.
  
  
  RESULTS
  A total 195 MRSA strains were included in this study; 87 were isolated patients with a clinical MRSA infection, and the other 108 strains from nasally colonized healthy children. Vancomycin MIC≥1.5 μg/mL was seen in more clinical isolates (60/87, 69%) than colonized isolates (32/108, 29.6%), p < 0.001. The PFGE typing of both strains revealed multiple pulsotypes.
  
  
  CONCLUSIONS
  Vancomycin MIC creeps existed in both clinical MRSA isolates and colonized MRSA strains. Great diversity of PFGE typing was in both strains collected. There was no association between the clinical and colonized MRSA isolates with vancomycin MIC creep.
authors: Department of Pediatrics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
authors: Chia-Ning
authors: CN
authors: Chang
authors: Department of Pediatrics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan; Department of Pediatrics, St. Joseph Hospital, Kaohsiung, Taiwan.
authors: Wen-Tsung
authors: WT
authors: Lo
authors: Infection Control Office, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
authors: Ming-Chin
authors: MC
authors: Chan
authors: Clinical Microbiology Laboratory Room, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
authors: Ching-Mei
authors: CM
authors: Yu
authors: Department of Pediatrics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan. Electronic address: ndmcccw@yahoo.com.tw.
authors: Chih-Chien
authors: CC
authors: Wang
mesh_terms: D000293:Adolescent; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002353:Carrier State / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D017576:Daptomycin / Q000494:pharmacology; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000382:microbiology*; D013624:Taiwan; D062606:Tertiary Care Centers; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin; D017576:Daptomycin
keywords: Methicillin-resistant Staphylococcus aureus; Pulsed-field gel electrophoresis type of MRSA; Vancomycin creep