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Epidemiology of Haemophilus influenzae invasive disease in Portugal, 2011-2016
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Advisor(s)
Abstract(s)
Introduction: Haemophilus influenzae, despite being a common commensal of the upper respiratory tract, is also an important pathogen, capable of causing severe invasive disease, in both children and adults. The epidemiology of invasive disease has changed since the introduction of Hib conjugate vaccines in 1990s, with a shift in the predominant serotype from Hib to non-capsulated H. influenzae (NTHi) and non-b serotypes.
Aims: We aim to characterize H. influenzae invasive isolates recovered in Portugal, over a 6-year period (2011-2016), and compare results with previous studies.
Materials and Methods: As part of a laboratory-based passive surveillance system, 174 invasive isolates, originated from 36 different Portuguese hospitals, were received at the National Reference Laboratory for Haemophilus influenzae. Capsular status was identified by PCR amplification of bexA gene and capsular type was determined by amplification of capsule-specific genes (a-f), as previously described.6 β-lactamase production was assessed with nitrocefin. Antibiotic susceptibility was determined by the microdilution assay, according to EUCAST guidelines. Genetic relatedness among the isolates was examined by MLST, by amplifying and sequencing internal fragments of the 7 housekeeping genes (adk, atpG, frdB, fucK, mdh, pgi, and recA), as previously described.7 Sequences were analysed and submitted to the MLST website (https://pubmlst.org/hinfluenzae/) for assignment of the sequence type (ST). To display the allelic distances between the obtained STs, goeBURST analysis was performed using the PHYLOViZ platform.
Results: Invasive disease was mainly due to NTHi strains (143/174; 82.2%). Encapsulated strains accounted to 17.8% of the isolates (31/174) and were characterized as follows: 12.9% serotype a (4/31), 67.7% serotype b (21/31), 6.5% serotype e (2/31), and 12.9% serotype f (4/31). Most strains were susceptible to the studied antibiotics, with 12.1% (21/174) of the isolates being β-lactamase producers.
MLST profiles revealed high genetic variability (71.3%), with 57 different STs among 80 NTHi isolates. In contrast, encapsulated strains were clonal; serotype b was assigned to CC6, (ST6 and ST190), serotype a to ST23, serotype e to ST18, and serotype f to ST124.
Conclusion: Invasive disease in Portugal is predominantly due to susceptible, highly genetically diverse NTHi strains, although non b type strains emerged after introduction of the Hib vaccine (5.7%). We are concerned with Hib strains (12.1%) which are still circulating in our country, especially in children (57.1%). Due to its evolving dynamics, ongoing surveillance is needed, in order to monitor the burden of the disease, and develop public health prevention strategies.
Description
Portuguese Group for the Study of Haemophilus influenzae invasive infection: Centro Hospitalar Baixo Vouga, Aveiro; Centro Hospitalar Barreiro / Montijo; Centro Hospitalar de Coimbra; Centro
Hospitalar de Faro; Centro Hospitalar do Porto; Centro Hospitalar do Tâmega e Sousa; Centro Hospitalar Leiria;
Centro Hospitalar Lisboa Central; Centro Hospitalar Lisboa Norte; Centro Hospitalar Lisboa Ocidental; Centro
Hospitalar Médio Ave / Famalicão; Centro Hospitalar Vila Nova de Gaia / Espinho; Hospital de Braga; Hospital de
Santa Luzia, Viana do Castelo; Hospital de Vila Franca de Xira; Hospital Dr. Fernando da Fonseca, Amadora; Hospital Dr. Nélio Mendonça, Funchal; Hospital Garcia da Orta, Almada; Hospital S. João , Porto
Keywords
Haemophilus Influenzae Pos-Hib Vaccine Serotypes MLST Invasive Haemophilus influenzae Disease Infecções Respiratórias Portugal