Molecular and phenotypic characterization of invasive group B streptococcus strains from infants in Norway 2006–2007

Multilocus sequence typing of an almost complete collection of invasive group B streptococcus (GBS) strains from infants in Norway, conducted in 2006–2007, revealed 27 sequence types (ST), of which 23 clustered into five clonal complexes. The case fatality rate of invasive GBS disease in infants was 16/98 (16.3%). Type V strains were predominant among strains resistant to erythromycin and clindamycin (11/18; 61.1%). All type V strains from fatal cases (5/16) were ST1, resistant to erythromycin and clindamycin, and belonged to three pulsed-field gel electrophoresis-clusters. Further analysis of virulence characteristics of these apparently highly virulent subtypes of type V, ST1 GBS strains is warranted.