In vitro activity of echinocandins against non-Candida albicans: is echinocandin antifungal activity the same?

Candida parapsilosis isolates carrying mutations outside FKS1 hotspot regions confer high echinocandin tolerance and facilitate the development of echinocandin resistance

Candida parapsilosis is a significant cause of candidemia worldwide. Echinocandin-resistant (ECR) and echinocandin-tolerant (ECT) C. parapsilosis isolates have been reported in various countries but are rare. Resistance and tolerance are predominantly caused by mutations related to the hotspot (HS) regions of the FKS1 gene. A relatively high proportion of clinical C. parapsilosis isolates carrying mutations outside the HS regions has been noted in some studies, but an association with echinocandin (EC) resistance or tolerance was not explored. Herein, CRISPR-Cas9 was used and the association between amino acid substitution in FKS1 outside HS 1/2 (V595I, S745L, M1328I, F1386S, and A1422G) with EC susceptibility profile was delineated. None of the mutations conferred EC resistance, but they resulted in a significantly higher level of EC tolerance than the parental isolate, ATCC 22019. When incubated on agar plates containing ECs, specifically caspofungin and micafungin, ECR colonies were exclusively observed among ECT isolates, particularly mutants carrying V595I, S745L, and F1386S. Additionally, mutants had significantly better growth rates in yeast extract peptone dextrose (YPD) and YPD containing agents inducing membrane and oxidative stresses. The mutants had a trivial fitness cost in the Galleria mellonella model relative to ATCC 22019. Collectively, this study supports epidemiological studies to catalog mutations occurring outside the HS regions of FKS1, even if they do not confer EC resistance. These mutations are important as they potentially confer a higher level of EC tolerance and a higher propensity to develop EC resistance, therefore unveiling a novel mechanism of EC tolerance in C. parapsilosis. The identification of EC tolerance in C. parapsilosis may have direct clinical benefit in patient management.

Pharmacoeconomic evaluation of micafungin versus caspofungin as definitive therapy for candidaemia and invasive candidiasis (IC) in Turkey

Micafungin was shown to be as efficacious as caspofungin in treating patients with candidaemia and invasive candidiasis (IC). However, it remains unknown if micafungin or caspofungin is a cost-effective definitive therapy for candidaemia and IC in Turkey. The present study aimed to determine the economic impact of using micafungin versus caspofungin for treatment of candidaemia and IC in the Turkish setting. A decision analytic model was constructed and was populated with data (i.e. transition probabilities, duration of initial antifungal treatment, reasons for treatment failure, percentage of patients who stepped down to oral fluconazole, and duration on oral fluconazole) obtained from a published randomised clinical trial. Cost inputs were derived from the latest Turkish resources while data that were not readily available in the literature were estimated by expert panels. One-way sensitivity analyses, threshold analyses, scenario analyses and probabilistic sensitivity analyses were conducted. Caspofungin (€2693) incurred a lower total cost than micafungin (€4422), with a net cost saving of €1729 per treated patient. Drug acquisition cost was the main cost driver for both study arms. The model outcome was robust over wide variations (of ±100.0% from the base case value) for all input parameters except for micafungin drug cost and the duration of initial treatment with micafungin. Caspofungin appears to be a cost-saving option in treating candidaemia and IC from the Turkish hospital perspective.

In vitro antifungal susceptibility of Candida glabrata to caspofungin and the presence of FKS mutations correlate with treatment response in an immunocompromised murine model of invasive infection

It has been argued that the in vitro activity of caspofungin (CSP) is not a good predictor of the outcome of echinocandin treatment in vivo. We evaluated the in vitro activity of CSP and the presence of FKS mutations in the hot spot 1 (HS1) region of the FKS1 and FKS2 genes in 17 Candida glabrata strains with a wide range of MICs. The efficacy of CSP against systemic infections from each of the 17 strains was evaluated in a murine model. No HS1 mutations were found in the eight strains showing MICs for CSP of ≤ 0.5 μg/ml, but they were present in eight of the nine strains with MICs of ≥ 1 μg/ml, i.e., three in the FKS1 gene and five in the FKS2 gene. CSP was effective for treating mice infected with strains with MICs of ≤ 0.5 μg/ml, showed variable efficacy in animals challenged with strains with MICs of 1 μg/ml, and did not work in those with strains with MICs of >1 μg/ml. In addition, mutations, including one reported for the first time, were found outside the HS1 region in the FKS2 gene of six strains with different MICs, but their presence did not influence drug efficacy. The in vitro activity of CSP was compared with that of another echinocandin, anidulafungin, suggesting that the MICs of both drugs, as well as mutations in the HS1 regions of the FKS1 and FKS2 genes, are predictive of outcome.

Posaconazole pharmacokinetics in a 2-year-old boy with rhino-cerebral-orbital zygomycosis

Posaconazole is a triazole antifungal agent used as adjuvant or salvage therapy for the treatment of zygomycosis, an invasive fungal infection associated with high mortality. Oral posaconazole absorption is highly variable. We describe the pharmacokinetics of oral posaconazole in a 2-year-old boy with rhino-cerebral-orbital zygomycosis. Seven days after induction therapy for acute lymphoblastic leukemia, he was brought to the emergency department because of left eyelid swelling and was admitted to the hospital. Zygomycosis was diagnosed 12 days later. After we conducted a literature search and consulted with antifungal drug experts, a triple-antifungal regimen consisting of liposomal amphotericin B, caspofungin, and posaconazole was started. Given the severity of the disease, we aimed for posaconazole plasma trough concentrations greater than 1.25 µg/ml; the dosage necessary to achieve this goal was posaconazole 200 mg 4 times/day. After a difficult 105-day stay in the hospital and stabilization of the fungal infection, the patient was discharged. Caspofungin was discontinued at time of discharge, but the patient continued to receive amphotericin B lipid complex 7.5 mg/kg/day intravenously and posaconazole 200 mg orally 4 times/day. This is one of the few case reports describing posaconazole pharmacokinetics in a child younger than 8 years. In patients with extensive zygomycosis, a triple-antifungal regimen, combined with therapeutic drug monitoring of posaconazole, may be helpful.

[Antifungal treatment options in the critically ill patient]

Invasive fungal infections, especially in the critical care setting, have become an excellent target for prophylactic, empiric, and pre-emptive therapy interventions due to their associated high morbidity, mortality rate, increased incidence, and healthcare costs. For these reasons, new studies and laboratory tests have been developed over the last few years in order to formulate an early therapeutic intervention strategy in an attempt to reduce the high mortality rate associated with these infections. In recent years, evidence-based studies have shown the roles that the new antifungal drugs play in the treatment of invasive mycosis in seriously ill and complex patients, although data from critically ill patients are more limited. New antifungal agents have been analyzed in different clinical situations in critical care units, and the increasing number of non-Candida albicans species suggest that the application of early echinocandin therapy in critically ill patients with invasive candidiasis is a good option. Voriconazole should be recommended for invasive aspergillosis as a first line option.

Candida guilliermondii: biotechnological applications, perspectives for biological control, emerging clinical importance and recent advances in genetics

Candida guilliermondii (teleomorph Meyerozyma guilliermondii) is an ascomycetous species belonging to the Saccharomycotina CTG clade which has been studied over the last 40 years due to its biotechnological interest, biological control potential and clinical importance. Such a wide range of applications in various areas of fundamental and applied scientific research has progressively made C. guilliermondii an attractive model for exploring the potential of yeast metabolic engineering as well as for elucidating new molecular events supporting pathogenicity and antifungal resistance. All these research fields now take advantage of the establishment of a useful molecular toolbox specifically dedicated to C. guilliermondii genetics including the construction of recipient strains, the development of selectable markers and reporter genes and optimization of transformation protocols. This area of study is further supported by the availability of the complete genome sequence of the reference strain ATCC 6260 and the creation of numerous databases dedicated to gene ontology annotation (metabolic pathways, virulence, and morphogenesis). These genetic tools and genomic resources represent essential prerequisites for further successful development of C. guilliermondii research in medical mycology and in biological control by facilitating the identification of the multiple factors that contribute to its pathogenic potential. These genetic and genomic advances should also expedite future practical uses of C. guilliermondii strains of biotechnological interest by opening a window into a better understanding of the biosynthetic pathways of valuable metabolites.

Comparative effects of micafungin, caspofungin, and anidulafungin against a difficult-to-treat fungal opportunistic pathogen, Candida glabrata

The aim of this study was to compare the in vitro and in vivo activities of micafungin, caspofungin, and anidulafungin against Candida glabrata. The MICs against 28 clinical isolates showed that the overall susceptibilities to caspofungin and to micafungin were not statistically different in the absence of human serum, whereas the isolates were less susceptible to micafungin than to caspofungin in its presence. Minimum fungicidal concentrations, as well as time-kill experiments, showed that caspofungin was more active than anidulafungin, while micafungin was superior to either caspofungin or anidulafungin without serum; its addition rendered caspofungin and micafungin equally effective. A murine model of systemic candidiasis against a C. glabrata-susceptible isolate was performed to study the effects of all three echinocandins, and kidney burden counts showed that caspofungin, micafungin, and anidulafungin were active starting from 0.25, 1, and 5 mg/kg of body weight/day, respectively. Two echinocandin-resistant strains of C. glabrata were selected: C. glabrata 30, a laboratory strain harboring the mutation Fks2p-P667T, and C. glabrata 51, a clinical isolate harboring the mutation Fks2p-D666G. Micafungin activity was shown to be as effective as or more effective than that of caspofungin or anidulafungin in terms of MICs. In vivo studies against these resistant strains showed that micafungin was active starting from 1 mg/kg/day, while caspofungin was effective only when administrated at higher doses of 5 or 10 mg/kg/day. Although a trend toward colony reduction was observed with the highest doses of anidulafungin, a significant statistical difference was never reached.