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J. Clin. Microbiol. doi:10.1128/JCM.02105-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The Population Structure of Invasive and Colonizing Strains of Streptococcus agalactiae from Neonates of Six U.S. Academic Centers from 1995 to 1999

The Department of Pediatrics and the Genome Center, University of Utah Health Sciences Center, Salt Lake City, UT; Faculté de Médicine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada; Department of Infectious Diseases, Children's Hospital Medical Center of Northern California, Oakland, CA; University of Alabama at Birmingham, Birmingham, AL; Baylor College of Medicine, Houston, TX; University of Dentistry and Medicine of New Jersey, Piscataway, NJ; National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD

^* To whom correspondence should be addressed. Email: john.bohnsack{at}hsc.utah.edu.

	Abstract

The purpose of this study was to describe the population structure of Group B streptococci (GBS) isolated from infected and colonized neonates during a prospective active surveillance study of early onset disease (EOD) in six centers in the United States from July 1995 to June 1999 and to examine its relationship to bovine strains of GBS. The phylogenetic lineage of each GBS isolate was determined by multi-locus sequence typing, and isolates were clustered into clonal complexes (CC) using eBURST. A total of 899 neonatal GBS isolates were studied, of which 129 were associated with invasive disease. Serotype Ia, Ib and V isolates were highly clonal, with 92% - 96% of serotype Ia, Ib and V isolates being confined to single clonal clusters. In contrast, serotype II and III isolates were each comprised of two major clones, with 39% of serotype II and 41% of serotype III isolates in CC 17, and 41% of serotype II and 54% of serotype III isolates in CC 19. Further analysis demonstrates that the CC 17 serotype II and III GBS are closely related to a previously described "ancestral" lineage of bovine GBS. While 120 (93%) of invasive GBS were confined to the same lineages that colonized neonates, 9 (7%) of the invasive GBS isolates were from rare lineages that comprised only 2.7% of colonizing lineages. These results are consistent with those of other geographic regions that demonstrate the highly clonal nature of GBS infecting and colonizing human neonates.