Antifolates inhibit Cryptococcus biofilms and enhance susceptibility of planktonic cells to amphotericin B
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The Cryptococcus neoformans species complex contains the most important agents of fungal meningoencephalitis. Therapeutic choices are limited and issues related to toxicity and resistance to antifungals have been described. The present study evaluated the inhibitory effect of the antifolate combinations sulfamethoxazole–trimethoprim (SMX/TMP) and sulfadiazine–pyrimethamine (SDZ/PYR) against planktonic cells and biofilms of C. neoformans and C. gattii. The influence of the antifolate combinations on the amphotericin minimum inhibitory concentration (MIC) of planktonic cells was also investigated. In addition, the effect of these combinations on the cellular ergosterol content of planktonic cells was studied. Strains of C. neoformans (n = 15) and C. gattii (n = 15) obtained from environmental or clinical sources were evaluated by the broth microdilution method. SMX/TMP and SDZ/PYR showed antifungal activity against free living cells and sessile cells of Cryptococcus spp. Moreover, planktonic cells showed increased susceptibility to amphotericin B after pre-incubation with sub-inhibitory concentrations of SMX/TMP or SDZ/PYR. The drug combinations SMX/TMP and SDZ/PYR were able to prevent the biofilm formation and showed inhibitory effect against mature biofilms of both species. Additionally, the study showed that antifolate drugs reduced the ergosterol content in C. neoformans and C. gattii planktonic cells. Our results highlight the antifungal potential of antifolate drugs.
KeywordsMinimum Inhibitory Concentration Ergosterol Planktonic Cell Yeast Nitrogen Base Ergosterol Content
This work was supported by grants from the National Council for Scientific and Technological Development (CNPq; Brazil; Processes 302574/2009-3 and 562296/2010-7). We would like to thank the Mycology Laboratory of the Evandro Chagas Clinical Research Institute in Rio de Janeiro (IPEC/FIOCRUZ) for providing the reference strains from its cryptococcal culture collection.
Conflict of interest
The authors declare that they have no conflict of interest.
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