title: Outbreak of late-onset group B Streptococcus in a neonatal intensive care unit.
abstract: BACKGROUND
  In September 2007, the Tennessee Department of Health was notified of a cluster of late-onset group B streptococcal (GBS) infections in a neonatal intensive care unit (NICU). Outbreaks of late-onset GBS are rare.
  
  
  METHODS
  A case was defined as culture-confirmed invasive GBS infection in a neonate aged > or =7 days, identified in hospital A during August 23 to September 6, 2007. We reviewed medical records; examined NICU microbiology reports; and performed serotyping, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) on invasive isolates. Maternal GBS screening, prophylaxis, and infection control policies were reviewed and staff practices observed.
  
  
  RESULTS
  Five cases of late-onset GBS were identified. None of the mothers of the infants received optimal GBS prophylaxis. Patient isolates were of 2 serotypes, 3 PFGE patterns, and 2 MLST patterns. Three isolates were indistinguishable on subtyping. These 3 cases were clustered in time. No common health care providers were identified. Infection control deviations in the NICU were observed.
  
  
  CONCLUSIONS
  We identified a multiclonal cluster of 5 late-onset GBS cases. Multiple factors likely contributed to the outbreak, including nosocomial transmission of GBS. Further efforts to prevent late-onset GBS disease are necessary.
authors.affiliation: Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA, USA. jmacfarquhar@hotmail.com
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: MacFarquhar
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Jones
authors.forename: Amy M
authors.initials: AM
authors.lastname: Woron
authors.forename: Marion A
authors.initials: MA
authors.lastname: Kainer
authors.forename: Cynthia G
authors.initials: CG
authors.lastname: Whitney
authors.forename: Bernard
authors.initials: B
authors.lastname: Beall
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Schrag
authors.forename: William
authors.initials: W
authors.lastname: Schaffner
mesh_terms: D015373:Bacterial Typing Techniques; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D016172:DNA Fingerprinting; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D008297:Male; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013290:Streptococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D013714:Tennessee / Q000453:epidemiology