MRSA transmission on a neonatal intensive care unit: epidemiological and genome-based phylogenetic analyses

PLoS One. 2013;8(1):e54898. doi: 10.1371/journal.pone.0054898. Epub 2013 Jan 31.

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) may cause prolonged outbreaks of infections in neonatal intensive care units (NICUs). While the specific factors favouring MRSA spread on neonatal wards are not well understood, colonized infants, their relatives, or health-care workers may all be sources for MRSA transmission. Whole-genome sequencing may provide a new tool for elucidating transmission pathways of MRSA at a local scale.

Methods and findings: We applied whole-genome sequencing to trace MRSA spread in a NICU and performed a case-control study to identify risk factors for MRSA transmission. MRSA genomes had accumulated sequence variation sufficiently fast to reflect epidemiological linkage among individual patients, between infants and their mothers, and between infants and staff members, such that the relevance of individual nurses' nasal MRSA colonization for prolonged transmission could be evaluated. In addition to confirming previously reported risk factors, we identified an increased risk of transmission from infants with as yet unknown MRSA colonisation, in contrast to known MRSA-positive infants.

Conclusions: The integration of epidemiological (temporal, spatial) and genomic data enabled the phylogenetic testing of several hypotheses on specific MRSA transmission routes within a neonatal intensive-care unit. The pronounced risk of transmission emanating from undetected MRSA carriers suggested that increasing the frequency or speed of microbiological diagnostics could help to reduce transmission of MRSA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Case-Control Studies
  • Female
  • Genetic Variation
  • Genome, Bacterial / genetics
  • Genomics*
  • Humans
  • Infant, Newborn
  • Intensive Care Units, Neonatal*
  • Male
  • Methicillin-Resistant Staphylococcus aureus / classification
  • Methicillin-Resistant Staphylococcus aureus / genetics*
  • Methicillin-Resistant Staphylococcus aureus / physiology*
  • Phylogeny*
  • Risk Factors
  • Staphylococcal Infections / epidemiology*
  • Staphylococcal Infections / microbiology
  • Staphylococcal Infections / transmission*

Grant support

MN received a fellowship from the European Programme for Intervention Epidemiology Training (EPIET), provided by the European Centre for Disease Prevention and Control, Stockholm, Sweden. The study was partially funded by a grant from the Institute of Medical Virology, University of Zürich, Switzerland (to KM). No additional external funding was received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.