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 (chi(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.