Yeast microbiota of free-ranging amphibians and reptiles from Caatinga biome in Ceará State, Northeast Brazil: High pathogenic potential of Candida famata / Leveduras da microbiota de anfíbios e répteis do bioma Caatinga no Ceará, Nordeste do Brasil: alto potencial patogênico de Candida famata

ABSTRACT: Studies on the fungal microbiota of reptiles and amphibians are necessary to better understand of host-microbe interactions and the establishment of fungal disease in these animals. However, these studies are limited. The present researchidentified yeasts from free-ranging reptiles and amphibians from the Caatinga biome andevaluated the virulence factors production, the antifungal susceptibility in planktonic and biofilm growth and the pathogenicity of Candida famata isolates. Twenty-nine isolates of the genera Candida, Cryptococcus and Rhodotorula were identified by phenotypic and/or molecular methods and production of hydrolytic enzymes in vitro by these genera of fungi was evaluated. In addition, susceptibility of planktonic cells and biofilms to azoles and amphotericin B was evaluated. The pathogenicity of C. famata, the most prevalent yeast species isolated, was evaluated using Caenorhabditis elegans model. C. famata was the most prevalent yeast in amphibian and reptilian microbiota. Phospholipase and protease production was observed in 18/29 and 11/29 of the yeast isolates, respectively, while 100% formed biofilms. Itraconazole presented high minimal inhibitory concentrations against C. famata and C. tropicalis. Amphotericin B reduced the biomass and metabolic activity of biofilms. C. famata induced the mortality of C. elegans. In conclusion, reptiles and amphibians are colonized by yeasts capable of producing important virulence factors, especially by Candida spp. that present low susceptibility to azoles which may result from imbalances in ecosystem. Finally, C. famata isolated from these animals presented high pathogenicity, showing the importance of the study of reptile and amphibians fungal microbiota.

RESUMO: Estudos sobre a microbiota fúngica de répteis e anfíbios são necessários para melhor compreender as interações hospedeiro-microrganismo e o estabelecimento de doenças fúngicas nesses animais. No entanto, esses estudos são limitados. O objetivo da presente pesquisa foi identificar leveduras isoladas de répteis e anfíbios do bioma Caatinga e avaliar a produção de fatores de virulência, a sensibilidade a antifúngicos no crescimento planctônico e de biofilme e a patogenicidade de Candida famata. Vinte e nove isolados dos gêneros Candida, Cryptococcus e Rhodotorula foram identificados por métodos fenotípicos e/ou moleculares e a produção de enzimas hidrolíticas in vitro por esses gêneros de fungos foi avaliada. Além disso, foi avaliada a suscetibilidade de células planctônicas e biofilmes a azólicos e anfotericina B. A patogenicidade de C. famata, a espécie de levedura isolada mais prevalente, foi avaliada usando Caenorhabditis elegans. C. famata foi a levedura mais prevalente na microbiota de anfíbios e répteis. A produção de fosfolipase e protease foi observada em 18/29 e 11/29 dos isolados de levedura, respectivamente, enquanto 100% formaram biofilmes. O itraconazol apresentou altas concentrações inibitórias mínimas contra C. famata e C. tropicalis. A anfotericina B reduziu a biomassa e atividade metabólica dos biofilmes. C. famata induziu a mortalidade de C. elegans. Em conclusão, répteis e anfíbios são colonizados por leveduras capazes de produzir importantes fatores de virulência, especialmente por cepas de Candida spp. que apresentam baixa suscetibilidade a azólicos que podem resultar de desequilíbrio no ecossistema. Por fim, C. famata isolados desses animais apresentaram alta patogenicidade, mostrando a importância do estudo da microbiota fúngica de répteis e anfíbios.

Terpinen-4-ol, tyrosol, and ß-lapachone as potential antifungals against dimorphic fungi

Abstract This study aimed to evaluate the in vitro antifungal activity of terpinen-4-ol, tyrosol, and β-lapachone against strains of Coccidioides posadasii in filamentous phase (n = 22) and Histoplasma capsulatum in both filamentous (n = 40) and yeast phases (n = 13), using the broth dilution methods as described by the Clinical and Laboratory Standards Institute, to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of these compounds. The mechanisms of action of these compounds were also investigated by analyzing their effect on cell membrane permeability and ergosterol synthesis. The MIC and MFCf these compounds against C. posadasii, mycelial H. capsulatum, and yeast-like H. capsulatum, were in the following ranges: 350-5720 µg/mL, 20-2860 µg/mL, and 40-1420 µg/mL, respectively for terpinen-4-ol; 250-4000 µg/mL, 30-2000 µg/mL, and 10-1000 µg/mL, respectively, for tyrosol; and 0.48-7.8 µg/mL, 0.25-16 µg/mL, and 0.125-4 µg/mL, respectively for β-lapachone. These compounds showed a decrease in MIC when the samples were subjected to osmotic stress, suggesting that the compounds acted on the fungal membrane. All the compounds were able to reduce the ergosterol content of the fungal strains. Finally, tyrosol was able to cause a leakage of intracellular molecules.

Antiretroviral drugs saquinavir and ritonavir reduce inhibitory concentration values of itraconazole against Histoplasma capsulatum strains in vitro

Abstract Recent studies have shown that some drugs that are not routinely used to treat fungal infections have antifungal activity, such as protease inhibitor antiretroviral drugs. This study investigated the in vitro susceptibility of Histoplasma capsulatum var. capsulatum to saquinavir and ritonavir, and its combination with the antifungal itraconazole. The susceptibility assay was performed according to Clinical and Laboratory Standards Institute guidelines. All strains were inhibited by the protease inhibitor antiretroviral drugs. Saquinavir showed minimum inhibitory concentrations ranging from 0.125 to 1 μg mL−1 for both phases, and ritonavir presented minimum inhibitory concentrations ranging from 0.0312 to 4 μg mL−1and from 0.0625 to 1 μg mL−1 for filamentous and yeast phase, respectively. Concerning the antifungal itraconazole, the minimum inhibitory concentration values ranged from 0.0019 to 0.125 μg mL−1 and from 0.0039 to 0.0312 μg mL−1 for the filamentous and yeast phase, respectively. The combination of saquinavir or ritonavir with itraconazole was synergistic against H. capsulatum, with a significant reduction in the minimum inhibitory concentrations of both drugs against the strains (p < 0.05). These data show an important in vitro synergy between protease inhibitors and itraconazole against the fungus H. capsulatum.

Simvastatin inhibits planktonic cells and biofilms ofCandida and Cryptococcusspecies

ABSTRACTThe antifungal activity of some statins against different fungal species has been reported. Thus, at the first moment, the in vitro antifungal activity of simvastatin, atorvastatin and pravastatin was tested againstCandida spp. and Cryptococcus spp. Then, in a second approach, considering that the best results were obtained for simvastatin, this drug was evaluated in combination with antifungal drugs against planktonic growth and tested against biofilms ofCandida spp. and Cryptococcus spp. Drug susceptibility testing was performed using the microdilution broth method, as described by the Clinical and Laboratory Standards Institute. The interaction between simvastatin and antifungals against planktonic cells was analyzed by calculating the fractional inhibitory concentration index. Regarding biofilm susceptibility, simvastatin was tested against growing biofilm and mature biofilm of one strain of each tested yeast species. Simvastatin showed inhibitory effect against Candida spp. andCryptococcus spp. with minimum inhibitory concentration values ranging from 15.6 to 1000 mg L-1 and from 62.5 to 1000 mg L-1, respectively. The combination of simvastatin with itraconazole and fluconazole showed synergism against Candidaspp. and Cryptococcus spp., while the combination of simvastatin with amphotericin B was synergistic only againstCryptococcus spp. Concerning the biofilm assays, simvastatin was able to inhibit both growing biofilm and mature biofilm ofCandida spp. and Cryptococcus spp. The present study showed that simvastatin inhibits planktonic cells and biofilms ofCandida and Cryptococcus species.