Saudi Cultural Missions Theses & Dissertations
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Item Restricted Antifungal tolerance in clinical isolates during the development of drug resistance(University of Birmingham, 2024-08-27) Alnafisi, Bassam; Ji Tsai, HungThe increasing prevalence of fungal diseases, particularly those caused by Candida albicans, presents a significant challenges for healthcare due to the rising number of immunocompromised individuals. C. albicans, an opportunistic pathogen, often transitions from a harmless commensal organism to a virulent pathogen under conditions of immune suppression, leading to a spectrum of infections from superficial to life-threatening systemic diseases. Despite advancements in antifungal therapies, infections caused by C. albicans remain associated with high mortality rates, highlighting the organism's complex mechanisms for evading host immune responses and developing drug resistance. This study investigates the evolution of drug tolerance and resistance in C. albicans clinical isolates, particularly in the context of fluconazole treatment. The research focuses on understanding the role of aneuploidy, heat shock response, and subpopulation dynamics in the development of tolerance. Through a series of experiments involving clinical isolates, the study tracks how C. albicans adapts over time in response to antifungal treatment. The results indicate that tolerance mechanisms are more pronounced at 37°C, a temperature reflective of the human body, underscoring the importance of thermal adaptation in the pathogenicity of C. albicans. Additionally, C. albicans clinical isolates exhibit tolerance in both broth and agar plate assays, a phenomenon attributed to a combination of specific genotypic and phenotypic characteristics. Our data support the initial hypothesis that the drug tolerance of C. albicans varies over different time points, reflecting the fungus's adaptive response to fluconazole exposure, particularly as influenced by temperature and subpopulation dynamics.29 0Item Restricted PolyEther Ether Ketone (PEEK) Containing the Antifungal Agent Nonanoic Acid as a Denture Base Material to Manage Candida albicans(University of Sheffield, 2024) Aldryhim, Hanan; Murdoch, CraigStatement of problem: Removable dentures are associated with denture stomatitis, caused by Candida albicans which has become increasingly resistant to common antifungal drugs. Purpose: The purpose of this study was to evaluate efficacy of different concentrations of nonanoic acid (C9 10%;1%;0.1%) loaded PEEK discs on inhibiting growth of C. albicans. Materials and methods: PEEK discs (1 mm diameter/2 mm thickness/N = 45) were fabricated; depending on group (n = 9/group) discs were loaded with either C9 (10%;1%;0.1%) or caspofungin (positive control) or no antifungal (negative control). The discs were cultured with C. albicans suspension and subjected to XTT (2,3-bis2-Methoxy-4-nitro-5-sulfophenyl-2H-tetrazolium-5-carboxyanilide) assay. Differences in mean optical density (OD) value between groups was compared using one-way ANOVA, at 95% level of statistical significance (p<0.05). One disc per group was subjected to scanning electron microscopy (SEM) for C. albicans adhesion on PEEK discs. Results: Mean OD values were significantly different between all groups (p<0.001), wherein lower OD value indicated greater inhibition of C. albicans growth. Caspofungin group had lowest mean OD (0.43±0.03), followed by 10%-C9 (0.84±0.03), 1%-C9 (1.24±0.04), 0.1%-C9 (1.52±0.04) and negative control (1.91±0.05). SEM analysis revealed pronounced quantity of C. albicans in negative control, however quantity decreased in the C9 groups as the concertation increased. Conclusion: Different concentrations of nonanoic acid (C9) loaded on PEEK discs significantly inhibited growth of C. albicans in culture, as evidenced by lower OD values after XTT essay. A dose response effect was observed with higher concentration of nonanoic acid resulting in significantly higher inhibition of C. albicans.22 0Item Restricted The non-pharmaceutical impact of silicon dioxide nanoparticles in the reduction of fungal growth (Candida albicans) on Vacuum Formed Retainers(University of Liverpool, 2028-07-17) Alshumrani, Abdullah; Allison, HeatherAims: This study investigates the efficacy of Silicon Dioxide Nanoparticle (SiO2 NP) coatings as a non-pharmaceutical approach to reduce or prevent oral candidiasis in patients using non-permanent orthodontic retainers, specifically vacuum formed retainers (VFRs). Methods: We utilised Cetyltrimethylammonium Bromide (CTAB)-tagged, spherical SiO2 NPs with an average diameter of 14 nm, applying them to the surfaces of 96 or 24-well microtiter plates to identify the optimal coating time. Following the nanoparticle coating, we assessed the adherence of Candida albicans (C. albicans) to coupons made from orthodontic materials. This assessment was performed using a stain release assay to compare the levels of adherence in the presence versus the absence of the SiO2 NP coating. This was complemented by a metabolic activity evaluation via resazurin dye and the examination of C. albicans's response under different growth media through light microscopy, aiming to elucidate the interaction dynamics between SiO2 NPs and C. albicans. Importance and Implications: The research underscores the potential of SiO2 NP coatings to diminish C. albicans colonisation on orthodontic retainers, offering a promising strategy to mitigate oral candidiasis risks associated with removable dental appliances. It lays the groundwork for future studies and clinical trials to explore the effectiveness of SiO2 NP coatings in maintaining oral health, particularly in the context of orthodontic retainer use. Results: Preliminary findings indicate that SiO2 NP-coated surfaces can reduce the attachment and metabolic activity of C. albicans, associated with its virulence, on polystyrene (PS) microtiter plates. However, an increase in biomass was observed on both treated and untreated orthodontic material coupons made of polyethylene terephthalate glycol (PETG). These results suggest a nuanced interaction between SiO2 NPs and C. albicans, highlighting the potential for SiO2 NP coatings to maintain C. albicans in a less virulent yeast form on polystyrene plastic surfaces, potentially enhancing wearer comfort without promoting the growth of other opportunistic pathogens.21 0Item Restricted Early-life snack and dietary supplement intake among underserved children and their role in early childhood caries(Saudi Digital Library, 2023-05-12) Alkadi, Ahmed; Xiao, JinIntroduction: Early childhood caries (ECC) is one of the most diseases in young children in the United States. Cariogenic microbes and snack intake may be linked to the development of ECC. Snack and supplement intake may vary oral PH properties and offer nutrients for bacterial growth and consequently affecting the colonization of cariogenic microbes. However, the relationship between snack and supplement intake and cariogenic microbes is largely unclear. Objectives: To assess the snack and diet supplement consumption among underserved birth cohort in the first two years of life and to assess the association between snacks and supplement intake and oral cariogenic microorganisms (S. mutans, Candida) carriage in early life. Methods: A prospective birth cohort was included in the analyses if the enrolled children had data on snack intake and cariogenic microorganisms (n=127). A questionnaire was used to collect the amount and frequency of intake of snacks and drinks at the 12-, 18- and 24-month visits. Diet supplement prescriptions were abstracted from medical records. Saliva and plaque were collected at the same time points to assess the quantity of S. mutans and Candida carriage Results: Overall, 25.4% of children who participated developed ECC by 2 years of age. At 24 months, the detection of S. mutans was nearly 50%, while C. albicans remained stable at 20% since birth. S. mutans was found in 60% of plaque samples, while C. albicans was found in only 20% at 24 months. Chips and fresh fruit were associated with an increased risk of C. albicans colonization (p<0.05). Cereals with milk were associated with an increased risk of S. mutans colonization (p<0.05). Yogurt appeared to be protective against C. albicans colonization, as well as Vitamin D was a protective factor against S. mutans colonization (p<0.05). Conclusion: Certain snacks and drinks were associated with the colonization C. albicans and S. mutans in early life. Intriguingly, yogurt and vitamin D were linked to reducing the colonization of C. albicans and S. mutans. Further investigation is needed to elucidate the underlying mechanisms involved in these relationships.39 0Item Restricted USE OF PHOTO-ACTIVATED DISINFECTION (PAD) METHOD FOR THE MANAGEMENT OF DENTAL CARIES BIOFILMS(2022) Almansour, Khulood; Banerjee, Avijit; Moyes, DavidBackground: Oral microbial diversity presents significant challenges to caries model and disinfection protocol development. The production of bacterial and fungal mixed biofilms is a particular concern. Notably, changing local environmental conditions is one of the primary activities of a biofilm. Therefore, for a better understanding of the interaction between fungi and bacteria in dental biofilms, it is important to design physiologically relevant multikingdom biofilms that mimic cariogenic activity and evaluate the impact of antimicrobial system on these cariogenic biofilm models. Objectives: The objectives in this study are divided into sections. Development of a cariogenic multispecies biofilm model in the presence and absence of the oral fungi Candida albicans using plaque and cariogenic species, and development of a cariogenic multispecies biofilm model in the presence and absence of plaque and cariogenic species. The influence of Candida albicans and sucrose on the biofilm models will next be evaluated, and the cariogenic potential of polymicrobial plaque biofilm models will be tested. Finally, the antimicrobial and post antimicrobial effect of PAD on the developed multispecies cariogenic model will be investigated. Materials and methods: Biofilms were developed using a combination of “commensal” (Streptococcus oralis, Actinomyces oris, Actinomyces viscosus) and caries-associated (Streptococcus mutans, Lactobacillus acidophilus) oral bacteria as well as the fungus Candida albicans. Bacteria and C. albicans were grown to stationary phase, then washed and resuspended in either RPMI or artificial saliva containing mucin. Bacteria were resuspended at 1X106 CFU/mL and C. albicans 1X105 CFU/mL. Single- and polymicrobial biofilms were then prepared in 24 well plates (1 microbe, 4 bacteria, 5 bacteria, 5 bacteria with L. acidophilus added 3rd day) with and without C. albicans and left for 5 or 10 days, with media changed daily for the first 5days. Then biomass and metabolic activity were measured using Crystal violet and XTT assays respectively to investigate the biofilms developed. For evaluating the impact of sucrose and C. albicans on the developed multispecies biofilm a selection of biofilm communities was prepared (4 bacteria (4), 5 bacteria (5L), 5 bacteria with L. acidophilus added third day (5L3)) with/without C. albicans and grown on hydroxyapatite discs for 10 days, with artificial saliva (AS) ± 0.2 % sucrose. AS was changed daily days 1-5, then left day 5-10. Biomass, metabolic activity, pH level and microbial abundance were measured using Crystal violet, XTT assays, pH meter and qPCR respectively. To determine cariogenic activity, 5L3 biofilms ± C. albicans were grown on polished human enamel and characterised by non-contact laser profilometry to measure surface roughness (Sa), Raman spectroscopy and Knoop microhardness (KHN). Further, to evaluate the Photoactive disinfection (PAD) impact, the multispecies biofilms were grown on hydroxyapatite discs in 24 opaque well plates. The media on the biofilms was changed daily for five days and then was not changed for five days as previously mentioned, resulting in biofilms that were 10 days old. Each experiment for biomass and metabolic activity, was conducted in triplicate, while microbial composition utilising qPCR was conducted twice. On day 10, all analyses were conducted. Biofilm biomass, metabolic activity and the species composition of biofilm was analysed utilising Crystal violet, XTT assays and quantitative polymerase chain reaction qPCR respectively. Results: Significantly higher biomass was observed in multikingdom biofilms aged 10 days grown on polystyrene substrate in artificial saliva compared to RPMI-culture media. While no difference in metabolic activity was observed in the same group. When multispecies biofilms grown on polished enamel substrate in AS media with and without 0.2 % sucrose, biofilms formed successfully. Sucrose affected the species composition, with S. mutans and C. albicans being more abundant in biofilms with sucrose versus non-sucrose media. However, in the absence of sucrose, S. mutans was reduced in Candida-containing versus Candida-free biofilms. A. oris and A. viscosus were reduced in Candida-containing biofilms in sucrose versus non-sucrose media. S. oralis abundance was higher in Candida-containing versus Candida-free biofilms and further increased in sucrose-containing media. In all biofilms and media, there was an increase surface roughness (Sa) of enamel. However, the 5L3 community with sucrose but without Candida resulted in significantly higher surface roughness (Sa). Raman spectroscopy indicated a significant loss of mineral content. The surface Knoop microhardness (KHN) was decreased in sucrose-containing biofilms. Furthermore, Candida-free biofilms with no sucrose had lower Knoop microhardness level (KHN) than Candida-containing biofilms. All biofilm media examined had a lower pH on day 10 than on day 1, with the sucrose groups more acidic medium (low pH value) than non-sucrose and the Candida-containing biofilms less acidic than Candida-free biofilms. PAD affected the biomass of all multikingdom biofilms while in Candida-free biofilms only biofilm 4 was affected significantly. Viability of all biofilm models were reduced significantly after PAD treatment and PAD showed an effect after 5 days of treatment. PAD showed an effect on the composition of all groups treated, resulting in biofilms composed mainly of Actinomyces seen in most biofilms 4, 5, 5, 5C and 5L3C. Conclusions: Artificial saliva containing mucin can provide a favourable environment for the growth of multikingdom biofilms in vitro. The presence of C. albicans with sucrose induces changes in the composition of biofilm species, which affects biofilm cariogenicity. The polymicrobial biofilms developed in this study formed cariogenic communities on the enamel surfaces within 10 days. Multikingdom biofilms and sucrose influence changes in biofilm species composition, which has an effect on biofilm cariogenicity. C. albicans decreases demineralisation while sucrose increases it. PAD therapy showed an effect on multispecies biofilm viability reduction. Tolonium chloride was worth mentioning since it had an effect on some biofilms when applied alone.25 0