title: MALDI-TOF MS typing of a nosocomial methicillin-resistant Staphylococcus aureus outbreak in a neonatal intensive care unit.
abstract: BACKGROUND
  The early detection of a methicillin-resistant Staphylococcus aureus (MRSA) outbreak is decisive to control its spread and rapidly initiate adequate infection control measures. Therefore, prompt determination of epidemiologic relatedness of clinical MRSA isolates is essential. Genetic typing methods have a high discriminatory power but their availability remains restricted. In this study, we aimed to challenge matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) as a typing tool of a nosocomial MRSA outbreak in a neonatal intensive care unit.
  
  
  METHODS
  Over a 2-year period, 15 MRSA isolates were recovered from patients (n = 14) and health care workers (n = 1) at the neonatal intensive care unit. Five reference strains were included for comparison. Identification was performed by MALDI-TOF MS and susceptibility profiles determined by automated broth microdilution. Typing analysis by MALDI-TOF MS included mean spectrum profiles and subsequent dendrogram creation using BioNumerics software. Results were compared with spa typing and pulsed-field gel electrophoresis (PFGE).
  
  
  RESULTS
  Our study showed good concordance (93%) between PFGE, spa typing, and MALDI-TOF MS for the outbreak-related MRSA strains. MALDI-TOF MS typing showed excellent typeability and discriminatory power but showed poor reproducibility.
  
  
  CONCLUSIONS
  This study is one of the first to document the potential usefulness of MALDI-TOF MS with standardized data analysis as a typing tool for investigating a nosocomial MRSA outbreak. A concordance of 93% compared to reference typing techniques was observed. However, because of poor reproducibility, long-term follow-up of prospective isolated strains is not practical for routine use. Further studies are needed to confirm our observations.
authors.affiliation: a Laboratoire de microbiologie , Cliniques universitaires Saint-Luc - Université catholique de Louvain , Brussels , Belgium.
authors.forename: Deborah
authors.identifier: http://orcid.org/0000-0002-8082-6587
authors.initials: D
authors.lastname: Steensels
authors.affiliation: b Department of Clinical Microbiology, National Reference Center S. aureus , ULB Erasme University Hospital , Brussels , Belgium.
authors.forename: Ariane
authors.initials: A
authors.lastname: Deplano
authors.affiliation: b Department of Clinical Microbiology, National Reference Center S. aureus , ULB Erasme University Hospital , Brussels , Belgium.
authors.forename: Olivier
authors.initials: O
authors.lastname: Denis
authors.affiliation: a Laboratoire de microbiologie , Cliniques universitaires Saint-Luc - Université catholique de Louvain , Brussels , Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: Simon
authors.affiliation: a Laboratoire de microbiologie , Cliniques universitaires Saint-Luc - Université catholique de Louvain , Brussels , Belgium.|c Institut de recherche expérimentale et Clinique (IREC), pôle de microbiologie (MBLG) , Université catholique de Louvain , Brussels , Belgium.
authors.forename: Alexia
authors.initials: A
authors.lastname: Verroken
mesh_terms: D015373:Bacterial Typing Techniques / Q000379:methods*; D003428:Cross Infection / Q000382:microbiology*; D004196:Disease Outbreaks; D006801:Humans; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013203:Staphylococcal Infections / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology*
keywords: MALDI-TOF MS; MRSA; Nosocomial outbreak; Standardized data analysis; Typing