Saudi Cultural Missions Theses & Dissertations

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    The effect of corticosteroids on sinus microbiota in chronic rhinosinusitis patients with nasal polyposis
    (McGill University, 2019) Alammar, Yousif; Rousseau, Simon; Tewfik, Marc; Rousseau, Simon; Tewfik, Marc
    Background: Chronic rhinosinusitis with nasal polyposis (CRSwNP) is a multifactorial disease with no known single cause, but it is thought that bacteria play a role in the disease process. The short-term response of bacterial communities to corticosteroid therapy has been found to be unpredictable. As a result, this pilot study aims to assess the long-term effect of corticosteroid therapy on sinus microbiota in chronic rhinosinusitis patients with nasal polyposis (CRSwNP). Methods: A longitudinal prospective case-control study was done on patients with CRSwNP and on healthy subjects. Patients with CRSwNP were randomly allocated to a maximal medical therapy (corticosteroids and antibiotics) treatment group or a corticosteroid-only treatment group. Data was collected at 3 time points (before treatment, 1 and 3 months after treatment): A guarded sinus swab was collected from the middle meatus; the SNOT-22 questionnaire was used to assess clinical symptoms. Specimens were cultured and Matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry (MS) was used as a bacterial detection method. The raw data produced was analyzed to characterize the sample and to assess the response to each medical treatment. Results: Data from 29 patients with CRSwNP (16 maximal medical therapy; 13 corticosteroids only) was compared to 15 healthy subjects. Patients reported significant symptoms improvement initially (1- month), but not on the long-term (3-months). This result was found as a response to both treatment groups, whether or not antibiotics was used. There was no significant difference in the sinus microbiota prevalence between CRSwNP patients and normal subjects. After three months from treatment, Corynebacterium genera tended to increase in the maximal medical therapy group, while Staphylococcus and gram-negative genera (Pseudomonas) tended to increase after corticosteroid treatment. Smoking, aspirin sensitivity and previous endoscopic sinus surgery were found to be co-factors significantly associated with the response to systemic corticosteroid therapy. Conclusion: In this pilot study both treatment options were effective on the short-term, but not on the long-term with no clear sinus microbiota response linked. As a result, this study agrees with previous reports that discourage the use of systemic antibiotics without evidence of active infection.
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    Alterations of Gut Microbiota due to External Stress and the Associated Health Outcomes – A Systematic Review
    (University of Aberdeen, 2023-01-18) Almubarak, Fatimah; MacCallum, Donna
    Background. Alterations of gut microbiota have been investigated for their association with many pathologies. Studies have reported significant changes to the composition and diversity of gut microbiota due to external stress using 16S ribosomal RNA sequencing. However, the threat of those alterations to the host's health is poorly studied. This systematic review was performed to explore the associated health outcomes with alterations of gut microbiota in mice exposed to external stresses. Methods. The database PubMed was searched for primary research papers published between 2013 and 2023, for case–control studies detecting gut microbiota in mice exposed to psychosocial, dietary, chemical, and environmental stress. The risk of bias in the studies was assessed using SYRCLE. The α-diversity and the abundance of gut microbiota in mice in stress groups compared to control groups were analysed qualitatively. Results. Eleven studies involving male or female mice were included. The risk of bias in the studies ranged from low to moderate risk. Faecal, caecal, and colonic samples showed no significant difference in the α-diversity of gut bacteria in approximately half of the studies and a lower diversity in the other half. Many variations in the abundance of gut bacteria from the same samples at the taxonomic levels of phylum, genus, family, and species. Conclusions. Alterations of gut microbiota were observed in mice after stress exposure and were thought to be associated with increased inflammation and other health outcomes. Further studies are needed to provide more evidence and explanation for the pathologies associated with changes to gut microbiota.
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