Neonatal Invasive Haemophilus influenzae Disease and Genotypic Characterization of the Associated Strains in Italy.

TO THE EDITOR—We read with interest the article by Collins and colleagues demonstrating that nontypeable Haemophilus influenzae (NTHi) is responsible for most invasive disease occurring in the perinatal period and that early-onset neonatal NTHi disease (strain isolation from blood or cerebrospinal fluid within 48 hours of birth) is strongly associated with premature birth [1]. Although it is well known that following the routine use of H. influenzae type b conjugate vaccines, most invasive H. influenzae disease is caused by NTHi. The value of the Collins’s study was to draw attention to neonatal invasive disease that, to date, has probably been underestimated [2–4]. According to the authors’ conclusions, a better understanding of the responsible NTHi strains through molecular characterization is needed [1]. In Italy, 13 invasiveH. influenzae disease cases were detected in infants aged ≤31 days through the National Surveillance of Invasive Bacterial Disease (1 January 2009–31 March 2015) (Figure 1, inset). Of 13 infants (all presenting with septicemia), 9 (69.2%) were born prematurely (<37 weeks of gestation) and 5 were male. Early-onset invasive infection occurred in 11 neonates (11/13, 84.6%); all but 2 were born prematurely (Figure 1, inset). At discharge, all neonates were alive, but 2 had long-term complications (1 had moderate neurological impairment and 1 had hypoacusis). Looking at maternal factors in early-onset infection, 3 mothers had fever, 3 had chorioamnionitis, and 1 experienced premature rupture of membranes. The 2 neonates who developed late-onset invasive disease (>48 hours after birth) were born at 37 weeks and >38 weeks. Of 13 H. influenzae strains, 10 were sent to the National Reference Laboratory (Istituto Superiore di Sanità, Rome, Italy) where they were characterized. Serotyping,