Correlation between microdilution, Etest, and disk diffusion methods for antifungal susceptibility testing of fluconazole against Candida sp. blood isolates

Effects of Euterpe oleracea Mart. extract on Candida spp. biofilms

PROBLEM OF RESEARCH

Candida spp. biofilms are complex microbial communities that have been associated with increasing resistance to clinically available antifungal drugs. Hence, novel pharmacological approaches with ability to inhibit biofilm formation have been investigated.

AIM OF STUDY

The aim was to analyze in vitro antifungal activity of Euterpe oleracea Mart. (açaí berry) extract on biofilm strains of Candida albicans, C. parapsilosis, and C. tropicalis that were formed on abiotic surfaces.

REMARKABLE METHODOLOGY

Biofilms of C. albicans, C. parapsilosis, and C. tropicalis were grown in vitro. They were then treated with E. oleracea Mart. extract at different concentrations (7.8, 15.6, 31.2, 62.5, 125, 250, 500, and 1000 μg/mL) for evaluation of both biofilm removal and anti-biofilm activity.

REMARKABLE RESULTS

All Candida species analyzed formed biofilms on abiotic surfaces. Yet, increased biofilm formation was displayed for C. tropicalis in comparison with the other two species. E. oleracea Mart. extract was shown to inhibit biofilm formation at all concentrations used when compared to no treatment (p < 0.05).

SIGNIFICANCE OF THE STUDY

In the current study, the extract of E. oleracea Mart. demonstrated antifungal activity against Candida albicans, C. parapsilosis, and C. tropicalis biofilms, regardless of the dose utilized. These results are important to evaluate a natural product as antifungal for Candida species.

Rapid detection of fluconazole resistance in Candida tropicalis by MALDI-TOF MS

With the changing epidemiology and emergence of antifungal resistance among Candida species, rapid antifungal susceptibility testing (AFST) is crucial for optimization of antifungal therapy. This study was conducted to standardize a matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI -TOF MS) based AFST method (ms-AFST) for susceptibility of Candida tropicalis isolates. Clinical isolates of C. tropicalis were confirmed for fluconazole resistance by the CLSI (M27-A3) method. The incubation period and drug concentration were optimized to determine the minimal profile change concentration (MPCC) by MALDI-TOF MS. The data were analyzed first by direct visual observation of the spectra followed by composite correlation index (CCI) matrix analysis, virtual gel analysis, and cluster analysis for confirmation. Finally, the correlation between minimum inhibitory concentrations (MICs) and MPCCs was evaluated. A total of 15 fluconazole resistant (MICs ranging from 16 to 128 μg/ml) and 19 fluconazole susceptible C. tropicalis isolates (MIC ≤1 μg/ml) were included in this study. All C. tropicalis isolates had significant spectral changes after 4h incubation with fluconazole. Of 34 isolates, MPCCs and MICs were equivalent for 16 isolates, and the MPCC was one dilution lower than the respective MIC in the remaining 18 isolates. This finding was further supported by visual analysis, CCI matrix analysis, virtual gel and principal component analysis dendrogram analysis. The correlation between MPCC and MIC was significant (P < .05). Therefore, a MALDI-TOF MS based AFST assay may be used as a rapid screening technique for fluconazole resistance in C. tropicalis.

Pre-mRNA splicing is modulated by antifungal drugs in the filamentous fungus Neurospora crassa

For this study, we sought to identify pre‐mRNA processing events modulated by changes in extracellular pH, inorganic phosphate, and antifungal drugs. We examined genes with at least four putative introns whose transcriptional level responded to these effectors. We showed that the intron retention levels of genes encoding asparagine synthetase 2, C6‐zinc finger regulator (fluffy), and a farnesyltransferase respond to amphotericin B, ketoconazole, and other effectors. In general, the assayed antifungals promoted the disruption of the structural domains of these proteins probably leading to their inactivation, which emphasize the complexity of the metabolic modulation exerted by antifungal signaling.