AUTHOR=Ekinci Esra , Willen Laura , Rodriguez Ruiz Juan Pablo , Maertens Kirsten , Van Heirstraeten Liesbet , Serrano Gabriela , Wautier Magali , Deplano Ariane , Goossens Herman , Van Damme Pierre , Beutels Philippe , Malhotra-Kumar Surbhi , Martiny Delphine , Theeten Heidi 

TITLE=Haemophilus influenzae carriage and antibiotic resistance profile in Belgian infants over a three-year period (2016–2018)

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1160073

DOI=10.3389/fmicb.2023.1160073

ISSN=1664-302X

ABSTRACT=<sec><title>Background</title><p>Non-typeable <italic>Haemophilus influenzae</italic> has become increasingly important as a causative agent of invasive diseases following vaccination against <italic>H. influenzae</italic> type b. The emergence of antibiotic resistance underscores the necessity to investigate typeable non-b carriage and non-typeable <italic>H. influenzae</italic> (NTHi) in children.</p></sec><sec><title>Methods</title><p>Nasopharyngeal swab samples were taken over a three-year period (2016–2018) from 336 children (6–30 months of age) attending daycare centers (DCCs) in Belgium, and from 218 children with acute otitis media (AOM). Biotype, serotype, and antibiotic resistance of <italic>H. influenzae</italic> strains were determined phenotypically. Mutations in the <italic>ftsI</italic> gene were explored in 129 strains that were resistant or had reduced susceptibility to beta-lactam antibiotics. Results were compared with data obtained during overlapping time periods from 94 children experiencing invasive disease.</p></sec><sec><title>Results</title><p>Overall, NTHi was most frequently present in both carriage (DCC, AOM) and invasive group. This was followed by serotype “f” (2.2%) and “e” (1.4%) in carriage, and “b” (16.0%), “f” (11.7%), and “a” (4.3%) in invasive strains. Biotype II was most prevalent in all studied groups, followed by biotype III in carriage and I in invasive strains. Strains from both groups showed highest resistance to ampicillin (26.7% in carriage vs. 18.1% in invasive group). A higher frequency of <italic>ftsI</italic> mutations were found in the AOM group than the DCC group (21.6 vs. 14.9% – <italic>p</italic> = 0.056). Even more so, the proportion of biotype III strains that carried a <italic>ftsI</italic> mutation was higher in AOM compared to DCC (50.0 vs. 26.3% – <italic>p</italic> &lt; 0.01) and invasive group.</p></sec><sec><title>Conclusion</title><p>In both groups, NTHi was most frequently circulating, while specific encapsulated serotypes for carriage and invasive group were found. Biotypes I, II and III were more frequently present in the carriage and invasive group. The carriage group had a higher resistance-frequency to the analyzed antibiotics than the invasive group. Interestingly, a higher degree of <italic>ftsI</italic> mutations was found in children with AOM compared to DCC and invasive group. This data helps understanding the <italic>H. influenzae</italic> carriage in Belgian children, as such information is scarce.</p></sec>