Invasive disease caused by H. influenzae non- b serotypes in children

Abstract

Background: Haemophilus influenzae (six serotypes,a-f and non typable) causes upper and lower respiratory infections and invasive disease. Invasive disease due to non-b Haemophilus influenzae is an emerging disease after the introduction of universal vaccination strategy for serotype b in infants and toddlers (1998) in Argentina. Although the first strain was isolated at the hospital in 1994 during the prevaccinal period. Aim: to describe the frequency for invasive disease. Methods & Materials: We prospectively studied 113 strains non-b H. influenzae invasive disease isolated from 109 children aged 1 month-10 years (1997-2015) at the Microbiology Department, Sor Maria Ludovica Children Hospital, La Plata, Argentina. Blood (Bact/Alert, Organon Teknika Corp), CSF, and samples from other normally sterile sites were cultured. Isolation was made by standard methods, and identification with DIFCOTM capsular specific serum (Detroit, Michigan, USA). Results: None to 13 strains were isolated per year. Frequency according to type of sample was: blood culture 76.1% (n = 86), pleural effusion 12.4% (n14); CSF 10.6% (n = 12), peritoneal fluid 0.9% (n = 1). The distribution by serotypes was: non typable 77.8% (n = 88); a, 9.7% (n = 11); c, 0.9% (n = 1); d, 1.8% (n = 2); e, 3.5% (n = 4); and f, 6.2% (n = 7). Twenty three strains (20.3%) were beta-lactamase positive. Clinical manifestations were: bacteremic pneumonia, 51.2% (n = 57), pneumonia and empyema, 11.9% (n = 13); meningitis, 11.0% (n = 12), bacteremia, 11.9% (n = 13); sepsis, 12.8% (n = 14); peritonitis, 0.9 (n = 1). Children < 2 years of age accounted for 92.7% cases (n = 101). Conclusion: With the success of H. influenzae b conjugate vaccine to prevent invasive disease (n = 104 for the studied period, 59 for years 1997-1998) we observed an increase for other serotypes although the number is reduced compared with the past impact of serotype b (>20 cases/year).