| Área: Micologia Médica ( Divisão B ) IN VITRO ACTIVITY OF TERBINAFINE AGAINST CRYPTOCOCCUS NEOFORMANS AND CRYPTOCOCCUS GATTII ISOLATES.
Caroline Rezende Guerra (UFRJ); Amanda da Silva Costa (UFRJ); Sonia Rozental (UFRJ)
Resumo
The yeasts Cryptococcus neoformans and Cryptococcus gattii cause cryptococosis in imunosuppressed and imunocompetent individuals, respectively. Nowadays, the treatment in Brazil is done with amphotericin B, fluconazole or itraconazole. However, frequent clinical failure has been reported. Terbinafine is an antifungal used mostly against dermatophytes but its activity in vitro and in vivo against several fungi has been shown. The aim of this work was to evaluate the effect of terbinafine and its combinations with other antifungals in C. neoformans and C. gattii isolates.
The antifungals used in this work were: amphotericin B, fluconazole, itraconazole and terbinafine. First, 23 C. neoformans and 11 C. gattii isolates were used for microdilution assays (M27-A3 protocol, CLSI 2008) in order to determine the inhibitory concentrations by spectrophotometric reading at 492nm, after 72h at 35ºC. Second, we determined the minimum fungicidal concentration (MFC) after transferring 5ml of each well of the microdilution plates onto sabouraud agar plates. After 72h, the MFC was considered the lowest concentration where there was no colony growth. In order to combine the drugs in vitro, we performed checkerboard assays between terbinafine and the other antifungal agents used in the treatment of cryptococosis. The microplates were incubated and read as described previously. Furthermore, we processed one isolate of each species for conventional transmission electron microscopy (TEM), to observe ultrastrucutural alterations caused by terbinafine treatment.
Cryptococcus sp. isolates were more susceptible to terbinafine, where 90% of the isolates had an inhibitory concentration of 50% of growth (IC50) up to 0,5mg/ml. Also, terbinafine showed a fungistatic effect due to high MFC values. Among the combinations tested, all had a synergistic effect. Moreover, there was a great reduction of the concentration of the drugs combined, compared to the IC50. In addition, TEM allowed us to see alterations in the cell wall structure, membrane detachment and an increase of cytoplasmatic vacuoles.
Thus, we believe that terbinafine, when used alone or in combination, has a good in vitro activity against Cryptococcus sp. Therefore, terbinafine can be used as an alternative in patients who do not respond to conventional treatment. However, clinical trials are needed.
Financial support: CNPq and FAPERJ
Palavras-chave: Cryptococcus neoformans, Cryptococcus gattii, Terbinafine, Transmission Electron Microscopy |