Incidence of invasive group B streptococcal disease and pathogen genotype distribution in newborn babies in the Netherlands over 25 years: a nationwide surveillance study

BACKGROUND: Group B streptococcus is the most common cause of neonatal infections. We studied the clinical and molecular epidemiology of invasive group B streptococcus infection in children younger than 3 months in the Netherlands over 25 years. We assessed the effect of the Dutch guidelines, introduced in 1999, for prevention of group B streptococcus, consisting of intravenous antibiotic prophylaxis during labour in cases of premature labour, prolonged rupture of membranes, or fever during delivery.

METHODS: We did this nationwide surveillance study with data from 1987 to 2011, from the Netherlands Reference Laboratory for Bacterial Meningitis. We included data for patients aged 3 months or younger with positive blood culture or cerebrospinal fluid culture for group B streptococcus and Escherichia coli infection. Early onset was defined as less than 7 days after birth and late onset was defined as 7 or more days after birth. We did multilocus sequence typing of a random subset of group B streptococcus samples to assess changes in sequence type (Mann-Kendall trend test) and the distribution of clonal complexes (χ(2) and Fisher exact test) before the introduction of prevention guidelines (1987-99) and afterwards (2000-11). We compared incidences and the distribution of clonal complexes before and after the introduction of guidelines.

FINDINGS: Most cases of group B streptococcus had early onset (696/1075; 65%). The incidence of invasive group B streptococcus infection increased from 0·20 per 1000 livebirths in 1987, to 0·32 per 1000 livebirths in 2011 (p<0·0001). The incidence of early-onset disease increased from 0·11 per 1000 livebirths to 0·19 per 1000 livebirths (p<0·0001). The incidence of invasive Escherichia coli infection was 0·05 in 1987, and 0·16 in 2011 (p=0·17). Early-onset group B streptococcus infection caused by isolates belonging to clonal complex 17 was more common in the post-implementation period than in the pre-implementation period (p=0·002).

INTERPRETATION: The introduction of prevention guidelines for invasive group B streptococcus disease in 1999 did not reduce the incidence of disease in neonates. The guidelines should be reassessed and alternative approaches to prevent infant invasive group B streptococcus disease should be sought.

FUNDING: National Institute of Public Health and the Environment, the European Union's seventh framework programme, Netherlands Organization for Health Research and Development, Academic Medical Center, and the European Research Council.