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Genomic diversity and antimicrobial resistance of Haemophilus influenzae associated to non-invasive disease in Portugal: what are the differences from invasive disease isolates?
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Orientador(es)
Resumo(s)
Haemophilus influenzae, a Gram-negative coccobacillus commensal of the human nasopharynx,
can cause invasive and non-invasive diseases. Introduction of H. influenzae serotype b vaccine led to
epidemiological changes worldwide. In Portugal, although extensive research on invasive disease has
been conducted since 1989, information on non-invasive disease is scarce.
Our study aims to characterize H. influenzae isolates obtained from non-invasive disease, in
Portugal between 2015 and 2022, through both phenotypic and genotypic analysis. Additionally, our
data will be compared to previously published data on invasive disease.
In this study, a total of 505 H. influenzae non-invasive isolates, were characterized. Capsular
serotype was characterized by conventional PCR and β-lactamase production was determined using
nitrocefin as substrate, for all isolates. Antimicrobial susceptibility patterns were assessed by
microdilution for 327 isolates, following the EUCAST guidelines. Mutations in the ftsI gene were
assessed for 63 isolates using whole genome sequencing (WGS). Multilocus sequencing typing (MLST)
was performed for 107 isolates to examine genetic diversity and sequence type (ST) was assigned in
PubMLST (https://pubmlst.org/organisms/haemophilus-influenzae/).
Most of the isolates (98.8%) were characterized as non-encapsulated, while encapsulated
isolates accounted for 1.2%: 0.4% Hia, 0.2% Hie, and 0.6% Hif. The majority of the isolates were
susceptible to all antimicrobial agents tested, although 12.1% showed ampicillin resistance due to βlactamase production. WGS analysis revealed that 47.6% of the isolates exhibited ftsI mutations
associated with ampicillin resistance and were characterized as gBLNAR. MLST analysis showed that
non-encapsulated strains were highly diverse, with 55.9% having distinct sequence types (STs). ST-1034
was the most common, representing 5.9% of the isolates, followed by ST-12 and ST-836, each
comprising 4.9% of the isolates.
In summary, our results indicate that, in Portugal, non-invasive disease is mainly associated to
non-encapsulated H. influenzae strains, that shows high genetic diversity and are susceptible to most
antimicrobial agents used in therapy.
Descrição
Tese de mestrado, Biologia Humana e Ambiente , 2023, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Doença não invasiva Haemophilus influenzae Serotipo Suscetibilidade aos antibióticos WGS Teses de mestrado - 2024