title: Transmission Clusters of Methicillin-Resistant Staphylococcus Aureus in Long-Term Care Facilities Based on Whole-Genome Sequencing.
abstract: OBJECTIVE To define how often methicillin-resistant Staphylococcus aureus (MRSA) is spread from resident to resident in long-term care facilities using whole-genome sequencing DESIGN Prospective cohort study SETTING A long-term care facility PARTICIPANTS Elderly residents in a long-term care facility METHODS Cultures for MRSA were obtained weekly from multiple body sites from residents with known MRSA colonization over 12-week study periods. Simultaneously, cultures to detect MRSA acquisition were obtained weekly from 2 body sites in residents without known MRSA colonization. During the first 12-week cycle on a single unit, we sequenced 8 MRSA isolates per swab for 2 body sites from each of 6 residents. During the second 12-week cycle, we sequenced 30 MRSA isolates from 13 residents with known MRSA colonization and 3 residents who had acquired MRSA colonization. RESULTS MRSA isolates from the same swab showed little genetic variation between isolates with the exception of isolates from wounds. The genetic variation of isolates between body sites on an individual was greater than that within a single body site with the exception of 1 sample, which had 2 unrelated strains among the 8 isolates. In the second cycle, 10 of 16 residents colonized with MRSA (63%) shared 1 of 3 closely related strains. Of the 3 residents with newly acquired MRSA, 2 residents harbored isolates that were members of these clusters. CONCLUSIONS Point prevalence surveys with whole-genome sequencing of MRSA isolates may detect resident-to-resident transmission more accurately than routine surveillance cultures for MRSA in long-term care facilities. Infect Control Hosp Epidemiol 2016;37:685-691.
authors.affiliation: 1Department of Epidemiology and Public Health,University of Maryland School of Medicine,Baltimore,Maryland,United States.
authors.forename: O Colin
authors.initials: OC
authors.lastname: Stine
authors.affiliation: 1Department of Epidemiology and Public Health,University of Maryland School of Medicine,Baltimore,Maryland,United States.
authors.forename: Shana
authors.initials: S
authors.lastname: Burrowes
authors.affiliation: 2Wellcome Trust Sanger Institute,Hinxton,Cambridge,United Kingdom.
authors.forename: Sophia
authors.initials: S
authors.lastname: David
authors.affiliation: 3Department of Pathology,University of Maryland School of Medicine,Baltimore,Maryland,United States.
authors.forename: J Kristie
authors.initials: JK
authors.lastname: Johnson
authors.affiliation: 1Department of Epidemiology and Public Health,University of Maryland School of Medicine,Baltimore,Maryland,United States.
authors.forename: Mary-Claire
authors.initials: MC
authors.lastname: Roghmann
mesh_terms: D003428:Cross Infection / Q000382:microbiology / Q000635:transmission*; D006787:Hospitals, Veterans / Q000706:statistics & numerical data; D006801:Humans; D008134:Long-Term Care / Q000706:statistics & numerical data; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000472:pathogenicity*; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011446:Prospective Studies; D013203:Staphylococcal Infections / Q000635:transmission*; D000073336:Whole Genome Sequencing / Q000379:methods