Publicação
Susceptibility of Candida biofilms to photodynamic treatment
| Resumo: | In recent decades, the incidence of fungal infections caused by Candida spp. has significantly increased. C. albicans is the most important pathogen within this genus, since it is the most commonly isolated. However, other Candida species have gained importance over the last years, namely C. glabrata and C. parapsilosis. The rise of strains highly resistant to conventional antifungal treatments has increased the research for development of new effective antifungal therapies. Antimicrobial Photodynamic Therapy (APDT) has been proposed as a therapy for a large variety of localized infections. The aim of this work was to study the antifungal photodynamic effect of a new benzophenoxazine compound – FSc – on C. glabrata, C. parapsilosis and C. albicans biofilms. Biofilms were treated with different FSc concentrations (50 μM – 500 μM) for 18 h and irradiated with a xenon arc lamp (600 ± 2 nm) at various light doses (8 J cm-2 – 50 J cm-2). The efficiency of photodynamic treatment mediated by two widely used dyes – Nile blue chloride and Protoporphyrin IX – on C. albicans biofilms was also evaluated. Biofilms were incubated with 300 μM of each dye for 18 h and irradiated with a light dose of 36 J cm-2. In order to understand the oxidative stress response of Candida species to APDT, suspensions of C. albicans, C. glabrata and C. parapsilosis were incubated with 2 mM and 20 mM of two oxidant agents, hydrogen peroxide and paraquat, for 3 h. The effect of these oxidants on both cell viability and induction of antioxidant enzymes was evaluated. The photoinactivation of Candida biofilms with either FSc or PpIX as a photosensitizer was able to reduce the cell viability. On the other hand, Nile blue-mediated APDT assays showed no effect on cell viability. In general, photoinactivation of Candida cells was dependent on the dye concentration and light dose delivered. Nevertheless, irradiation with increasing light doses only resulted in a slight decrease of biofilm viability. Although the results of this study are encouraging, further investigations are needed to optimize protocols for maximal cell inactivation. Candida species showed high levels of resistance to the two oxidant agents, with the exception of C. glabrata that presented a greater sensitivity to paraquat. Generally, all Candida strains responded to hydrogen peroxide and paraquat exposure by increasing their content of catalase and superoxide dismutase, respectively. In summary, the data suggest that Candida species have different levels of resistance to oxidant agents and they use different defense mechanisms against these substances, showing differences in the induction of antioxidant enzymes. |
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| Autores principais: | Gomes, Marisa Conceição Lima |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | In recent decades, the incidence of fungal infections caused by Candida spp. has significantly increased. C. albicans is the most important pathogen within this genus, since it is the most commonly isolated. However, other Candida species have gained importance over the last years, namely C. glabrata and C. parapsilosis. The rise of strains highly resistant to conventional antifungal treatments has increased the research for development of new effective antifungal therapies. Antimicrobial Photodynamic Therapy (APDT) has been proposed as a therapy for a large variety of localized infections. The aim of this work was to study the antifungal photodynamic effect of a new benzophenoxazine compound – FSc – on C. glabrata, C. parapsilosis and C. albicans biofilms. Biofilms were treated with different FSc concentrations (50 μM – 500 μM) for 18 h and irradiated with a xenon arc lamp (600 ± 2 nm) at various light doses (8 J cm-2 – 50 J cm-2). The efficiency of photodynamic treatment mediated by two widely used dyes – Nile blue chloride and Protoporphyrin IX – on C. albicans biofilms was also evaluated. Biofilms were incubated with 300 μM of each dye for 18 h and irradiated with a light dose of 36 J cm-2. In order to understand the oxidative stress response of Candida species to APDT, suspensions of C. albicans, C. glabrata and C. parapsilosis were incubated with 2 mM and 20 mM of two oxidant agents, hydrogen peroxide and paraquat, for 3 h. The effect of these oxidants on both cell viability and induction of antioxidant enzymes was evaluated. The photoinactivation of Candida biofilms with either FSc or PpIX as a photosensitizer was able to reduce the cell viability. On the other hand, Nile blue-mediated APDT assays showed no effect on cell viability. In general, photoinactivation of Candida cells was dependent on the dye concentration and light dose delivered. Nevertheless, irradiation with increasing light doses only resulted in a slight decrease of biofilm viability. Although the results of this study are encouraging, further investigations are needed to optimize protocols for maximal cell inactivation. Candida species showed high levels of resistance to the two oxidant agents, with the exception of C. glabrata that presented a greater sensitivity to paraquat. Generally, all Candida strains responded to hydrogen peroxide and paraquat exposure by increasing their content of catalase and superoxide dismutase, respectively. In summary, the data suggest that Candida species have different levels of resistance to oxidant agents and they use different defense mechanisms against these substances, showing differences in the induction of antioxidant enzymes. |
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