title: Molecular epidemiological analysis of methicillin-resistant Staphylococcus aureus isolates from a medical intensive care unit: a comparison of nasal and clinical isolates.
abstract: BACKGROUND
  The control of nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA) represents a significant challenge to infection control professionals. Nasal carriage colonization by MRSA plays a crucial role in the epidemiology and pathogenesis of this infection.
  
  
  METHODS
  Patients in the medical intensive care unit (ICU) between November 2010 and March 2011 were swabbed when hospitalized, reswabbed 1 week later and for a third time, when they were discharged from the ICU. All swabs were examined within 2 hours of collection using ChromID MRSA-Select agar plates to detect MRSA. Positive specimens were determined to have the mecA and femB gene through amplification with duplex polymerase chain reaction. Repetitive element sequence-based polymerase chain reaction was used to investigate the epidemiological types of MRSA isolates in the third screening and clinical isolates obtained from 2007 to 2010 in West China Hospital. A comparison of molecular types was performed to investigate the genetic relationship between nasal and clinical isolates.
  
  
  RESULTS
  After the third screening, 16 nasal MRSA isolates were identified. Epidemiological analysis revealed that 16 nasal MRSA isolates and 37 clinical MRSA isolates differentiated into 2 clusters, comprising 9 subclusters. Of the 16 nasal strains, 11 (68.8%) belonged to subcluster I of cluster I; 3 of 9 subclusters consisted of both nasal and clinical isolates, while 4 of 9 subclusters consisted of clinical isolates and only 2 of 9 consisted of nasal isolates.
  
  
  CONCLUSIONS
  Our study indicated a high degree of genetic relatedness between nasal and clinical MRSA isolates. The molecular typing of MRSA is critical for controlling the nosocomial transmission of this pathogen in ICU setting and defining a nosocomial infection control policy.
authors.affiliation: Department of Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Limei
authors.initials: L
authors.lastname: Luo
authors.forename: Yi
authors.initials: Y
authors.lastname: Xie
authors.forename: Chao
authors.initials: C
authors.lastname: He
authors.forename: Fu
authors.initials: F
authors.lastname: Qiao
authors.forename: Hongdi
authors.initials: H
authors.lastname: Zhuang
authors.forename: Liang
authors.initials: L
authors.lastname: Guo
authors.forename: Weijia
authors.initials: W
authors.lastname: Yin
authors.forename: Mei
authors.initials: M
authors.lastname: Kang
authors.forename: Lanlan
authors.initials: L
authors.lastname: Wang
mesh_terms: D006801:Humans; D007362:Intensive Care Units; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification*; D017720:Molecular Epidemiology; D009297:Nasal Mucosa / Q000382:microbiology*; D011446:Prospective Studies; D013203:Staphylococcal Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics; D013211:Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification