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Title: Intermicrobial interactions in prosthetic speech valve biofilms
Authors: Abdullah, Syatirah Najmi
Issue Date: 2018
Publisher: Newcastle University
Abstract: Treatment of advanced head and neck cancers sometimes requires laryngectomy which extends the patient’s life span but makes natural speech impossible. Insertion of a silicone tracheoesophageal speech valve (TESV) can restore functional speech. This prosthesis frequently develops biofilm, causing valve obstruction and failure which will lead to infection to the wearer. Biofilms isolated from TESVs are usually polymicrobial with Candida albicans proposed as the main problematic agent. This study aimed to isolate, identify and model the biofilm community of TESVs. It is anticipated that improved understanding of intermicrobial interactions in TESV biofilms will lead to new approaches for biofilm control. Ten TESV biofilms were collected and microorganisms identified using ‘microbial culturomics’ involving standard culture techniques, biochemical tests, microscopy, mass spectrometry and next generation sequencing. C. albicans was always present; and often with at least one other fungal species together with a complex bacterial population that included H202-producing Lactobacillus spp. Possibly related to this, we found some TESV derived C. albicans spp. to be relatively resistant to peroxide-based reactive oxygen species. Species from a single TESV were tested for co-aggregation and an in vitro static biofilm model was developed to reflect the typical TESV biofilm composition. This model was used to assess the ability of different fungi and bacteria to compete within biofilms using quantitative PCR. Bacteria in the biofilm have a significant effect on the composition of Candida spp. and also impacted on the activation of the Hog1 stress-activated protein kinase in Candida spp. In conclusion, this is the first study of TESV biofilms employing microbial culturomics for identification and provides evidence that the composition is more complex than a simple candidal infection. This study is also the first to show that C. albicans Hog1 activation is inhibited in polymicrobial biofilms containing clinically relevant bacteria
Description: PhD Thesis
Appears in Collections:School of Dental Sciences

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