Characteristics of Meningococcal Invasive Disease in Neonates and Virulence of the Corresponding Isolates.

Background: The highest incidence of invasive meningococcal disease (IMD) is observed in infants. However, its prevalence in neonates (≤28 days of age) and the characteristics of the corresponding isolates are less described. This report aimed to analyze meningococcal isolates from neonates.

Methods: We first screened the database of the national reference center for meningococci in France for confirmed neonatal IMD cases between 1999 and 2019. We then performed whole-genome sequencing on all cultured isolates, and we evaluated their virulence in a mouse model.

Results: Fifty-three neonatal cases of IMD (mainly bacteremia) were identified (50 culture-confirmed cases and 3 PCR-confirmed cases) of a total of 10,149 cases (0.5%) but represented 11% of cases among infants of under 1 year of age. Nine cases (17%) occurred among neonates of 3 days of age and younger (early onset). The neonate isolates were often of serogroup B (73.6%) and belonged to the clonal complex CC41/44 (29.4%) with at least 68.5% of coverage by vaccines against serogroup B isolates. The neonatal isolates were able to infect mice although to variable levels.

Conclusion: IMD in neonates is not rare and can be of early or late onsets suggesting that anti-meningococcal vaccination can target women planning to have a baby.