In vitro effects of selective serotonin reuptake inhibitors on Cryptococcus gattii capsule and biofilm.

Infections caused by Cryptococcus gattii mainly affect immunocompetent individuals and the treatment presents important limitations. This study aimed to validate the efficacy of selective serotonin reuptake inhibitors (SSRI), fluoxetine hydrochloride (FLH), and paroxetine hydrochloride (PAH) in vitro against C. gattii. The antifungal activity of SSRI using the microdilution method revealed a minimal inhibitory concentration (MIC) of 31.25 µg/ml. The combination of FLH or PAH with amphotericin B (AmB) was analyzed using the checkerboard assay and the synergistic effect of SSRI in combination with AmB was able to reduce the SSRI or AmB MIC values 4-8-fold. When examining the effect of SSRI on the induced capsules, we observed that FLH and PAH significantly decreased the size of C. gattii capsules. In addition, the effects of FLH and PAH were evaluated in biofilm biomass and viability. The SSRI were able to reduce biofilm biomass and biofilm viability. In conclusion, our results indicate the use of FLH and PAH exhibited in vitro anticryptococcal activity, representing a possible future alternative for the cryptococcosis treatment.

Avaliação dos efeitos antifúngicos de fármacos inibidores seletivos da recaptação de serotonina em Cryptococcus gattii / Evaluation of the antifungal effects of selective serotonin reuptake inhibitors in Cryptococcus gattii

A criptococose é uma infecção fúngica que acomete tanto indivíduos imunocomprometidos como imunocompetentes. O arsenal antifúngico é limitado, existem relatos de desenvolvimento de resistência fúngica a esses compostos e também alta toxicidade ao paciente. O reposicionamento de fármacos dos inibidores seletivos da recaptação de serotonina (ISRS) tem mostrado ação contra espécies fúngicas, tornando estes compostos alternativas a serem estudadas para o tratamento das infecções criptocócicas. Assim, o objetivo deste estudo foi avaliar os efeitos antifúngicos em cápsula, biofilme e células planctônicas de Cryptococcus gattii (cepa ATCC 56990 e isolado clínico 5) dos fármacos ISRS, cloridrato de fluoxetina (CF) e cloridrato de paroxetina (CP). Para isso, foi utilizada a técnica de microdiluição em caldo de acordo com European Committee on Antimicrobial Susceptibility Testing (EUCAST) para determinar a Concentração Inibitória Mínima (CIM), sendo a CIM de 31,25 µg/mL determinada para os fármacos CF e CP e ambos os fármacos demonstraram ação fungicida (CIM/CFM = 1). Em seguida foi verificado atividade sinérgica dos fármacos CF e CP combinados com anfotericina B (AmB), como resultado encontramos três concentrações sinérgicas, para CF reduzindo 8 e 4x em relação ao valor de CIM, para CP reduzindo 4x em relação ao valor de CIM e para AmB houve redução de 4x em relação ao valor de CIM. Posteriormente, o efeito dos fármacos mencionados foi avaliado na redução da biomassa do biofilme, por meio da técnica de cristal violeta. Nas concentrações 10x (312,5 µg/mL) e 20x (625 µg/mL) CIM de observou-se a redução da biomassa do biofilme de C. gattii em 57,72% a 76,66% para CF e redução entre 42,69 a 68,03% para CP. Além disso, em concentrações sub- inibitórias, ambos fármacos reduziram o tamanho da cápsula da levedura em até 62,46% para CF e 58,94% para CP. Também foi analisada a viabilidade do biofilme pela contagem de unidades formadoras de colônia/mL, após tratamento com CF e CP 20x valor de CIM e foi observada redução entre 1,21 a 1,446 log na viabilidade do biofilme (p< 0,0001). Ainda, o efeito dos fármacos em biofilme foi avaliado quanto ao efeito na atividade metabólica pelo ensaio XTT nas concentrações 10x e 20x CIM de ambos os fármacos foi possível observar redução entre 39,05% a 84,62% para CF e redução entre 56,99% a 67,64% para CP. Assim, os fármacos avaliados apresentaram potencial antifúngico frente C. gattii em todos os ensaios in vitro, podendo ser considerados novas alternativas para o tratamento deste patógeno (AU)

Cryptococcosis is a fungal infection that affects both immunocompromised and immunocompetent individuals. The antifungal arsenal is limited, there are reports of the development of fungal resistance to these compounds and also high toxicity to the patient. The drug repositioning of selective serotonin reuptake inhibitors (SSRIs) has shown action against fungal species, making these compounds alternatives to be studied for the treatment of cryptococcal infections. Thus, the aim of this study was to evaluate the antifungal effects on capsule, biofilm and planktonic cells of Cryptococcus gattii (ATCC strain 56990 and clinical isolate 5) of the SSRI drugs, fluoxetine hydrochloride (FLH) and paroxetine hydrochloride (PAH). For this, the broth microdilution technique was used according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) to determine the Minimum Inhibitory Concentration (MIC), and the MIC of 31.25 µg/mL was determined for the drugs (FLH) and PAH and both drugs demonstrated fungicidal action (MIC/CFM = 1).Then it was verified synergistic activity of the drugs FLH and PAH combined with amphotericin B (AmB), as a result we found three synergistic concentrations, for FLH reducing 8 and 4x compared to the MIC value, for PAH reducing 4x compared to the MIC value and for AmB there was 4x reduction compared to the MIC value. Subsequently, the effect of the mentioned drugs was evaluated in the reduction of biofilm biomass by means of the crystal violet technique. At 10x (312.5 µg/mL) and 20x (625 µg/mL) MIC concentrations of it was observed the reduction of C. gattii biofilm biomass by 57.72% to 76.66% for FLH and reduction between 42.69 to 68.03% for PAH. Furthermore, at sub-inhibitory concentrations, both drugs reduced the yeast capsule size by up to 62.46% for FLH and 58.94% for PAH. The biofilm viability was also analyzed by counting colony forming units/mL, after treatment with FC and CP 20x the MIC value and a reduction between 1.21 to 1.446 log in biofilm viability was observed (p< 0.0001). Also, the effect of the drugs in biofilm was evaluated as the effect on the metabolic activity by the XTT assay in concentrations 10x and 20x MIC of both drugs was possible to observe reduction between 39.05% to 84.62% for FC and reduction between 56.99% to 67.64% for CP. Thus, the drugs evaluated showed antifungal potential against C. gattii in all in vitro assays, and may be considered new alternatives for the treatment of this pathogen.(AU)