title: Genetic differences between invasive and noninvasive neonatal group B streptococcal isolates.
abstract: BACKGROUND
  Streptococcus agalactiae, also known as group B streptococcus (GBS), is the most common cause of neonatal sepsis and meningitis. To improve our understanding of the pathogenesis of neonatal GBS sepsis, better knowledge of clonal relatedness and diversity among invasive and noninvasive GBS isolates is critical.
  
  
  METHODS
  In a Germany-based study, invasive neonatal GBS isolates were compared with noninvasive isolates from neonates in whom sepsis was suspected, but whose blood cultures were sterile. The comparison was conducted by means of pulsed-field gel electrophoresis and surface protein gene profiling. In addition, multilocus sequence typing was performed on invasive and noninvasive isolates of the most frequent invasive serotype III.
  
  
  RESULTS
  Pulsed-field gel electrophoresis analysis of noninvasive GBS showed a remarkably more diverse fingerprinting pattern than that of invasive isolates. In contrast to invasive strains, noninvasive isolates did not show any clustering. Surface protein gene profiling also showed significantly different distribution patterns between the 2 panels of isolates. Multilocus sequence typing of invasive and noninvasive serotype III isolates revealed the same clonal complexes, but displayed different sequence types (ST); ST-17 was most common (68.6%) among invasive strains, whereas ST-389 (clonal complex-19) was predominant among noninvasive strains (47.8%).
  
  
  CONCLUSIONS
  Our results illustrate a large molecular diversity among neonatal noninvasive GBS strains. Invasive strains, however, represent only a small proportion of the noninvasive GBS population. These findings suggest a selection process that prefers more virulent strains during invasion.
authors.affiliation: Center for Pediatrics and Adolescent Medicine, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Fluegge
authors.forename: Juliana
authors.initials: J
authors.lastname: Wons
authors.forename: Barbara
authors.initials: B
authors.lastname: Spellerberg
authors.forename: Sabrina
authors.initials: S
authors.lastname: Swoboda
authors.forename: Anette
authors.initials: A
authors.lastname: Siedler
authors.forename: Markus
authors.initials: M
authors.lastname: Hufnagel
authors.forename: Reinhard
authors.initials: R
authors.lastname: Berner
mesh_terms: D016009:Chi-Square Distribution; D016521:Electrophoresis, Gel, Pulsed-Field; D005858:Germany; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000382:microbiology*; D017720:Molecular Epidemiology; D058885:Multilocus Sequence Typing; D012703:Serotyping; D013290:Streptococcal Infections / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000235:genetics* / Q000302:isolation & purification