Lavado, Maria Paula BajancaDias, Deodália Maria Antunes, 1952-Duarte, Sara Joana Gonçalinho2024-04-1020242024http://hdl.handle.net/10451/64115Tese de mestrado, Biologia Humana e Ambiente , 2023, Universidade de Lisboa, Faculdade de CiênciasHaemophilus 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.engDoença não invasivaHaemophilus influenzaeSerotipoSuscetibilidade aos antibióticosWGSTeses de mestrado - 2024master thesis203606132