Invasive group B streptococcal disease in infants: a 19-year nationwide study. Serotype distribution, incidence and recurrent infection.

During the period 1984-2002, 472 cases of invasive group B streptococcal (GBS) disease in infants aged 0-90 days in Denmark were registered. The overall incidence was 0.4/1000 live births. Most infants (73%) had early-onset GBS infection with 53% registered within the first day. Serotype III predominated (59%) with other serotypes as follows: Ia (16%), Ib (8%), NT (7%), II (6%), other serotypes (5%). Recurrence of GBS infection was registered in six infants, and the interval with no antibiotic therapy varied from 2 to 39 days. The serotypes of the isolates obtained from first and second episodes were identical (serotype III in five, and serotype Ia in one infant). Paired isolates were indistinguishable by PFGE and antibiotic susceptibility testing. Invasive GBS infections in infants are still a problem in Denmark, and recurrent infections are registered in 1% of these infants.