title: Clinical and Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in a Neonatal Intensive Care Unit in the Decade following Implementation of an Active Detection and Isolation Program.
abstract: Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent source of infection in the neonatal intensive care unit (NICU), often associated with significant morbidity. Active detection and isolation (ADI) programs aim to reduce transmission. We describe a comprehensive analysis of the clinical and molecular epidemiology of MRSA in an NICU between 2003 and 2013, in the decade following the implementation of an MRSA ADI program. Molecular analyses included strain typing by pulsed-field gel electrophoresis, mec and accessory gene regulator group genotyping by multiplex PCR, and identification of toxin and potential virulence factor genes via PCR-based assays. Of 8,387 neonates, 115 (1.4%) had MRSA colonization and/or infection. The MRSA colonization rate declined significantly during the study period from 2.2 to 0.5/1,000 patient days (linear time, P = 0.0003; quadratic time, P = 0.006). There were 19 cases of MRSA infection (16.5%). Few epidemiologic or clinical differences were identified between MRSA-colonized and MRSA-infected infants. Thirty-one different strains of MRSA were identified with a shift from hospital-associated to combined hospital- and community-associated strains over time. Panton-Valentine leukocidin-positive USA300 strains caused 5 of the last 11 infections. Staphylococcal cassette chromosome mec (SCCmec) types II and IVa and agr groups 1 and 2 were most predominant. One isolate possessed the gene for toxic shock syndrome toxin; none had genes for exfoliative toxin A or B. These results highlight recent trends in MRSA colonization and infection and the corresponding changes in molecular epidemiology. Continued vigilance for this invasive pathogen remains critical, and specific attention to the unique host, the neonate, and the distinct environment, the NICU, is imperative.
authors.affiliation: Division of Perinatal Medicine, Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, USA.
authors.forename: Melissa U
authors.initials: MU
authors.lastname: Nelson
authors.affiliation: Division of Perinatal Medicine, Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Bizzarro
authors.affiliation: Division of Infectious Disease, Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, USA Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut, USA Department of Hospital Epidemiology, Yale-New Haven Hospital, New Haven, Connecticut, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Baltimore
authors.affiliation: Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut, USA Department of Hospital Epidemiology, Yale-New Haven Hospital, New Haven, Connecticut, USA Division of Infectious Disease, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA.
authors.forename: Louise M
authors.initials: LM
authors.lastname: Dembry
authors.affiliation: Division of Perinatal Medicine, Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, USA Department of Pathology, Yale University School of Medicine, New Haven, Connecticut, USA Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA patrick.gallagher@yale.edu.
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Gallagher
mesh_terms: D004269:DNA, Bacterial / Q000235:genetics; D062665:Epidemiological Monitoring; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D060005:Genotyping Techniques; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000302:isolation & purification*; D017720:Molecular Epidemiology; D058889:Molecular Typing; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000453:epidemiology*; D037521:Virulence Factors / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D037521:Virulence Factors