Clinically relevant members of the fungal genus, Fusarium, exhibit an extraordinary genetic diversity and cause a wide spectrum of infections in both healthy individuals and immunocompromised patients. Generally, Fusarium species are intrinsically resistant to all systemic antifungals. We investigated whether the presence or absence of the ability to produce biofilms across and within Fusarium species complexes is linked to higher resistance against antifungals. A collection of 41 Fusarium strains, obtained from 38 patients with superficial and systemic infections, and three infected crops, were tested, including 25 species within the Fusarium fujikuroi species complex, 14 from the Fusarium solani species complex (FSSC), one Fusarium dimerum species complex, and one Fusarium oxysporum species complex isolate. Of all isolates tested, only seven strains from two species of FSSC, five F. petroliphilum and two F. keratoplasticum strains, recovered from blood, nail scrapings, and nasal biopsy samples, could produce biofilms under the tested conditions. In the liquid culture tested, sessile biofilm-forming Fusarium strains exhibited elevated minimum inhibitory concentrations (MICs) for amphotericin B, voriconazole, and posaconazole, compared to their planktonic counterparts, indicating that the ability to form biofilm may significantly increase resistance. Collectively, this suggests that once a surface adherent biofilm has been established, therapies designed to kill planktonic cells of Fusarium are ineffective.

Although invasive fungal infections (IFIs) are relatively rare, they are important causes of morbidity and mortality in immunocompromised pediatric patients. Early and precise diagnosis of IFI is important to allow antifungal treatment to be started in time and to reduce the unnecessary use of toxic antifungal agents. Although traditional approaches such as direct microscopic examination, histopathological evaluation and cultivation are still gold standard, the diagnosis of IFI is generally difficult because of inadequate sensitivity and specificity with these tests. Commercial systems detecting the Aspergillus cell wall antigen galactomannan and 1,3-β-D-glucan are seen as the most convenient nonculture methods for the diagnosis of the IFI and monitoring of antifungal treatment. Several molecular methods have been described for the diagnosis of opportunistic mycoses. However, they have not been standardized and have only been used in experimental studies.

Introduction. The simultaneous use of antifungals with immunosuppressive agents has become a necessity for patients taking immunosuppressive therapy. However, antifungal drugs are problematic because of their limited target. Hypothesis. Scientists have been searching for new antifungals and some compounds with at least additive effects on antifungals. Calcineurin inhibitors used as immunosuppressive agents also attract attention due to their antifungal property. Aim. To evaluate the activity of two calcineurin inhibitors alone and in combination with amphotericin B (AMB), caspofungin (CAS), itraconazole (ITR), voriconazole (VOR) and fluconazole (FLU). Methodology. MICs of AMB, CAS, ITR, VOR, FLU and cyclosporine A (CsA) and tacrolimus (TAC) as calcineurin inhibitors were evaluated by the broth microdilution method against Candida albicans (n=13), C. krusei (n=7) and C. glabrata (n=10). Checkerboard and time-kill methods were performed to investigate the activity of combining calcineurin inhibitors with antifungal drugs. Results. The lowest MIC values were detected with VOR for all Candida isolates tested. Although we did not detect any inhibition for CsA or TAC alone at concentrations tested in this study, the combinations of CAS with CsA showed the highest synergistic activity (36.7%) by the checkerboard method, and CAS with CsA and ITR with TAC combinations exhibited apparent synergistic interaction by the time-kill method. However, the combinations of both CsA and TAC with AMB resulted in antagonistic interactions, especially against C. krusei isolate in time-kill testing. Conclusion. Synergistic interactions in the combinations of TAC or CsA with antifungal drugs, except for AMB, in many concentrations was found to be promising in terms of the treatment of patients with fungal infections.