With the recent emergence of candidemia as a significant cause of mortality in our health care system, clinicians must identify methods to minimize the sequelae of infection of this type in patients already burdened with serious underlying conditions. While well established as a major cause of blood stream infection (BSI), candidemia has been shown to have some of the highest rates of inappropriate therapy when compared to infections from all other sources. Rates of inappropriate therapy may be even higher for some of the less common and antifungal resistant non-albicans candidemia. Identifying those patients at risk for the development of these types of infections will help improve clinical outcomes. Antifungal activity is dependent both on species and agent, describing the unique susceptibility patterns between Candida species can help identify the appropriate therapy. We performed a case-case-control study to identify clinical risk factors for the development of Candida glabrata candidemia compared to Candida albicans candidemia and an uninfected control using multivariate and logistic regression analysis. We observed that patients in the C. glabrata cohort were more likely to have gastrointestinal disorders and peripheral vascular disease than patients suffering from C. albicans BSIs. We also determined that when compared to the uninfected control group, patients with C. glabrata BSIs were more likely to have been prior colonized with C. glabrata, undergone dialysis, and have been catheterized with both arterial and urinary catheters. We concluded that patient exposure to unique clinical risk factors may be predictive of the development of future candidemia and may help distinguish between albicans versus non-albicans candidemia. We performed a drug susceptibility study using time-kill methods with the echinocandin antifungal agents on Candida parapsilosis and two newly identified species of Candida, C. orthopsilosis and C. metapsilosis. The echinocandins as a group displayed primarily fungistatic activity against the clinical isolates tested. However, we observed substantial variability in antifungal activity that varied by both the echinocandin used and Candida species analyzed. We concluded that this variability in activity that is both species and drug dependent should be considered when selecting the treatment of candidemia resulting from these non-albicans species.

C. glabrata est une levure commensale de l’Homme à l’origine d’infections opportunistes chez les patients immunodéprimés. Les neutrophiles sont les premières cellules recrutées sur le site de l’infection. La production de formes réactives de l’oxygène par ces cellules, initiée dans le phagosome par la NADPH oxydase 2 est un évènement majeur de la maturation du phagosome et fait l’objet de l’étude réalisée. L’objectif de ce travail était de développer des outils expérimentaux permettant l’évaluation du stress oxydant subi par C. glabrata lors de son internalisation par les phagocytes. La levure non pathogène S. cerevisiae, phylogénétiquement plus proche de C. glabrata, a été choisie comme organisme contrôle permettant une étude comparative entre les deux levures. C. glabrata est efficacement internalisée en absence d’opsonisation, par la lignée PLB-985-neutrophile contrairement à S. cerevisiae. L’utilisation de sondes organiques pour la mesure des FRO dans le phagosome est limitée puisque que le marquage des levures par ces sondes n’est pas spécifiquement localisé. Le développement de biosenseurs de FRO à partir de protéines fluorescentes, dont la localisation est maitrisée grâce à un système de marquage, est présenté. Les études réalisées suggèrent cependant que les protéines fluorescentes subissent des modifications dans le phagosome indépendantes de la production de FRO. Des tests de viabilité effectués sur les levures après phagocytose montrent que l’élimination des levures dépend fortement de facteurs indépendants de la production de FRO. Plusieurs méthodes indiquent néanmoins que les phagosomes avec C. glabrata contiennent moins de FRO que les phagosomes avec S. cerevisiae. C. glabrata semble éliminer les FRO plus efficacement que S. cerevisiae. / C. glabrata is a human commensal yeast responsible for opportunistic infections in immunocompromised patients. Neutrophils are the first cells to be recruited to the infection site. Production of reactive oxygen species (ROS) in the phagosome by the phagocyte NADPH oxidase 2 is a major event of the phagosome maturation and is the subject of the study. The aim of this work was to develop experimental tools allowing the evaluation of the oxidative stress endured by C. glabrata during its internalization by phagocytes. The non-pathogenic yeast S. cerevisiae, phylogenetically close to C. glabrata, was chosen as a control organism allowing a comparative study between the two yeasts. Unlike S. cerevisiae, non-opsonized C. glabrata is efficiently internalized by the PLB-985 cell line. The utilization of organic dyes for the detection of ROS in the phagosome lacks precision since the staining of the yeasts by those dyes is not specifically localized. The development of ROS biosensors based on fluorescent proteins, whose localization can be controlled due to a new staining procedure, is presented here. However the results suggest that fluorescent proteins undergo modifications in the phagosome independently from the ROS production. Viability tests performed on the yeasts after phagocytosis showed that yeast removal depends mainly on factors independent from ROS production. Several methods indicate nevertheless that the phagosomes of C. glabrata contain less ROS than the phagosome of S. cerevisiae. C. glabrata appears to suppress ROS more efficiently than S. cerevisiae.

Orientador: Ana Claudia Pavarina / Resumo: O fungo Candida albicans, em situações de desequilíbrio imunológico no hospedeiro, pode se tornar um patógeno oportunista e provocar infecções. Tendo em vista a resistência que os microrganismos desenvolveram a fármacos convencionais, a Terapia Fotodinâmica Antimicrobiana (aPDT) vem apresentando resultados promissores como uma terapia alternativa. O objetivo deste estudo foi avaliar o potencial que aPDT possuiu em desenvolver resistência, tolerância ou susceptibilidade em C. albicans em associação com o Photodithazine (PDZ- 25 µg/L; 660 nm; 18 J/cm2) e Curcumina (CUR- 40 µg/L; 455 nm; 18 J/cm2) plaqueados em meio sem e com suplementação de Fluconazol (8 µg/L). C. albicans (ATCC 90028) em culturas planctônicas e biofilme foram submetidas à aplicações sucessivas de aPDT (10 aplicações), como também, a ciclos de recuperação e re-cultivo das colônias que sobreviveram ao tratamento até o momento que não houvesse mais células viáveis para a recuperação e continuação das aplicações. O plaqueamento foi realizado em placas de Ágar Sabourand Dextrose suplementadas ou não com Fluconazol, e os valores das unidades formadoras de colônia por mililitro (UFC/mL) foram determinados. O teste de produção de espécies reativas de oxigênio (ERO) foi realizado nos primeiros e últimos ciclos de aPDT. O perfil biomolecular das células sobrevivetes as aplicações 1, 4 e 7 de aPDT mediada por PDZ foi investigado através do teste de RT-qPCR. Foi observado no grupo tratamento de aPDT (P+L+) mediada por P... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The fungus Candida albicans, in situations of immune imbalance in the host, can become an opportunistic pathogen and cause infections. Because of the resistance that microorganisms have developed to conventional drugs, Antimicrobial Photodynamic Therapy (aPDT) has shown promising results as an alternative therapy. The main goal of this study was to evaluate the potential of aPDT to develop resistance in C. albicans in association with Photodithazine (PDZ-25 µg/L; 660 nm; 18 J/cm2) and Curcumin (CUR-40 µg/L; 455 nm; 18 J/cm2) grown with and without Fluconazole (8 µg/L). C. albicans (ATCC 90028), in planktonic and biofilm cultures, were submitted to successive applications of aPDT (10 applications), as well as cycles of recovery and re-cultivation of colonies that survived treatment until no longer viable cells were present for application recovery and continuation. Plating was performed on Sabourand Dextrose Agar plates supplemented or not with Fluconazole, and values of colony forming units per milliliter (CFU/mL) were determined. The reactive oxygen species (ROS) production test was performed in the first and last cycles of aPDT. The biomolecular profile of surviving cells as applications 1, 4 and 7 of PDZ-mediated aPDT was investigated using the RT-qPCR test. PDZ-mediated treatment of aPDT (P+L+) was observed to reduce approximately 6.8 log10 in planktonic cultures and approximately 6.2 log10 in C. albicans biofilm in both methodologies used. In the aPDT (C+L+) treatment gr... (Complete abstract click electronic access below) / Mestre

Orientador: Juliana Campos Junqueira / Banca: João Manoel Theotonio dos Santos / Banca: Liliana Scorzoni / Resumo: A Esclerose Múltipla (EM) é uma doença inflamatória, autoimune, crônica e desmielinizante que acomete o Sistema Nervoso Central (SNC). Sua etiologia ainda não é bem definida, mas vários fatores de risco podem estar associados à doença, incluindo fatores genéticos e ambientais. Recentemente, tem sido sugerido que a microbiota do indivíduo pode ter influência na EM. Sendo assim, o objetivo desse estudo foi investigar a relação entre EM e infecções fúngicas orais. Foram selecionados 100 indivíduos, sendo 55 com diagnóstico de EM pelos Critérios de McDonald (2017) e 45 indivíduos saudáveis (grupo controle). Amostras de saliva foram coletadas e semeadas em meios de culturas seletivos para o gênero Candida, incluindo ágar Sabouraud Dextrose com cloranfenicol e CHROMagar Candida. Após período de incubação de 48 horas, foi realizada a contagem do número de Unidades Formadoras de Colônias (UFC/mL), e as colônias isoladas foram submetidas à análise de PCR multiplex para identificação da espécie de Candida. Os resultados foram analisados pelos testes estatísticos de Qui-quadrado e Mann-Whitney, considerando-se nível de significância de 5%. Foi verificado presença de Candida spp. na cavidade bucal de 50,09% dos pacientes do grupo EM e de 35,55% dos indivíduos do grupo controle. Nos indivíduos com crescimento positivo para Candida spp., a mediana do número de colônias de Candida observadas foi de 220 UFC/mL para o grupo EM e 120 UFC/mL para o grupo controle. Entretanto, não foram observadas diferenças estatisticamente significantes entre os grupos tanto para a prevalência como contagem de UFC/mL. Em relação a identificação das espécies de Candida, foi encontrado 73,91% de C. albicans, 21,73% de C. glabrata, 2,17% de C. tropicalis e 2,17% de C. krusei. Concluiu-se que a presença de Candida spp. na cavidade bucal de indivíduos com EM foi mais elevada em relação ao grupo controle / Abstract: Multiple Sclerosis (MS) is an inflammatory, autoimmune, chronic and demyelinating disease that affects the Central Nervous System (CNS). Its etiology is not yet well defined, but several risk factors may be associated with the disease, including genetic and environmental factors. Recently, it has been suggested that the individual's microbiota may have influence on MS. Therefore, the objective of this study was to investigate the relationship between MS and oral fungal infections. A total of 100 individuals were selected, 55 of them diagnosed with MS by the McDonald Criteria (2017) and 45 healthy individuals (control group). Saliva samples were collected and seeded in culture medias selectives for the Candida genus, including Sabouraud Dextrose agar with chloramphenicol and CHROMagar Candida. After incubation period of 48 hours, the number of Colony Forming Units (CFU / mL) was counted and the colonies were isolated for identification of the Candida species by multiplex PCR. The results were analyzed by Chi-square and Mann-Whitney statistical tests considering a significant level of 5%. It was verified the presence of Candida spp. in the oral cavity of 50.09% of the patients in the MS group and 35.55% of the individuals in the control group. In individuals with positive growth for Candida spp., the median of Candida colonies observed was 220 CFU/mL for the MS group and 120 CFU/mL for the control group. However, no statistically significant differences were observed between the groups for both prevalence and CFU/mL count. In relation to the identifications of Candida species, it was found 73.91% of C. albicans, 21.73% of C. glabrata, 2.17% of C. tropicalis and 2.17% of C. krusei. It was concluded that the presence of Candida spp. in the oral cavity of individuals with MS was higher than the control group / Mestre

Objectives: Candida glabrata is the second most common cause of oral candidiasis, second only to C. albicans. Incidence of antifungal resistance has shown a steady increase for C. glabrata. Iron has shown to modulate C. albicans pathogenesis and affect drug-susceptibility. Here, we assess the effect of iron on the growth, antifungal-susceptibility, biofilms, and cell wall of C. glabrata.Methods: Growth, minimal inhibitory concentration (MIC), and biofilm experiments were conducted using 96-well polystyrene plates. Yeast Nitrogen Base medium was used for growth experiments. Cultures of C. glabrata and C. albicans were grown over two nights in respective media containing varying iron concentrations. Rosewell Park Memorial Institute medium was used for MIC and biofilm experiments. Serial dilution was performed to obtain desired concentrations of antifungal drugs. For all experiments, growth was assessed at OD600nm over 24 hours using BioTek Synergy Multi Mode Reader. Paraformaldehyde treated cells and specific stains were used for cell wall studies. Results: Growth of C. glabrata declined significantly below 5μM iron, while C. albicans continued to grow at decreasing iron concentrations, up to 0.5μM. MIC experiments revealed 1.562μM, 1.562μM, and 4μM, as the MIC for Deferasirox, Nystatin, and Fluconazole, respectively. Drug synergy experiments revealed a 128-fold reduction in the amount of Nystatin and Fluconazole needed, with the addition of 1/8th of Deferasirox concentration. The biofilm experiments were inconclusive and the cell wall studies showed decreased levels of mannan, chitin, and an increased β-glucan exposure in high iron conditions. Conclusion: C. glabrata is more sensitive to alterations in environmental iron when compared to C. albicans. Drug synergy experiments underscore the importance of Deferasirox in lowering the MICs of Nystatin or Fluconazole. This can allow use of classical antifungals at lower doses, thereby limiting their side effects. Cell wall studies discuss the effect of iron on the virulence of the C. glabrata. / Oral Biology

No description available.

Invasive fungal infections are a significant clinical challenge especially for hospitalized patients as traditional antifungal therapy often fails to resolve these infections. The ability of Candida to undergo yeast-to-hyphae morphological transition is central to this invasive behavior. Morphogenesis is also important for the formation of biofilms which are highly structured communities of microorganisms attached to one another or substratum and embedded within a protective extracellular matrix material. The refractory nature of cells within a biofilm to current antifungal therapies has created a need for alternative antifungal agents for the management of Candida biofilm-related infections. The novel antifungal occidiofungin is a natural product produced by the soil bacteria Burkholderia contaminans shown to be effective against a broad range of fungi including Candida spp. Prior studies have demonstrated that occidiofungin inhibits yeast-to-hyphae morphogenesis in the dimorphic yeast, C. albicans, likely through its impact on disrupting F-actin organization. To extend these findings, the efficacy of occidiofungin on morphogenesis of C. albicans and C. tropicalis strains under different inducing conditions was evaluated. Further, given the role of biofilm on pathogenicity, the anti-biofilm properties of occidiofungin against Candida species was examined using an in vitro static biofilm model developed on a silicon elastomer disk. The accumulated data indicate that occidiofungin inhibits hyphal transformation regardless of the inducing conditions used and prevents hyphal extension when added to cells post switching. Moreover, morphologically switching cells were more sensitive to occidiofungin than their yeast counterpart. In addition, occidiofungin effectively blocks biofilm formation at all stages of development and reduces dispersed cells from the biofilm for both C. albicans and C. tropicalis. Confocal data revealed alterations in actin organization with occidiofungin treatment for both morphologically switching and biofilm cells. These findings correlate with prior observations for occidiofungin activity on yeast form cells indicating the broad activity of occidiofungin against fungi at various stages of pathogenic growth and supports efforts to pursue occidiofungin as a potential therapeutic against Candida based infections.

The virulence of the opportunistic fungal pathogen Candida albicans is in part due to its ability to switch between a yeast and hyphal form; permitting physical rupture and escape from macrophages after phagocytosis. This interesting feature makes C. albicans a good model organism to study in the context of phagosome maturation and in particular, the role of the small GTPase Rab14 in this process. Rab14 is recruited to bacterial phagosomes containing Chlamydia trachomatis (Capmany & Damiani, 2010) and Mycobacterium bovis BCG (Kyei et al, 2006) and aids their survival in macrophages but its role in phagosomes containing fungal pathogens is not known. Here, an important role for Rab14 in protecting macrophages against hyphal mediated lysis by C. albicans is demonstrated. Macrophages were transfected to express eGFP-Rab14, or dominant negative variants (eGFP-Rab14 S25N and eGFP-Rab14N124I); or were transfected with anti-Rab14 siRNA; then infected with live C. albicans and observed using sophisticated live cell imaging and analysis tools. Phagosomes containing live C. albicans became transiently Rab14-positive within 2 minutes following engulfment. Interestingly, a prolonged retention of Rab14 on phagosomes depended on C. albicans morphology. Phagosomes containing hyphal forms retained Rab14 for twice as long as for phagosomes containing the yeast form. Depletion of endogenous Rab14 did not affect macrophage migration towards C. albicans, the rate of engulfment or acquisition of markers of early phagosome maturation to phagosomes containing C. albicans. Furthermore, reduced Rab14 expression did not influence the kinetics of Rab5 localisation to phagosomes in macrophages that were co-transfected. Importantly, partially depleting Rab14 delayed the appearance of late phagosome maturation indicators LAMP1 and activated cathepsin in phagosomes containing live C. albicans.Rab14 knockdown was associated with a significant increase in macrophage killing by C. alibica The data presented in this thesis demonstrate the dynamic relationship between host and pathogen which can be visualised in real time at the level of individual phagosomes. Rab14 plays an important role during phagosome maturation which impacts on the later stages of phagosome maturation and is important for phagocyte survival after phagocytosis of C. albicans.

published_or_final_version / Paediatrics / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Dentistry / Doctoral / Doctor of Philosophy