Multicenter study of isavuconazole MIC distributions and epidemiological cutoff values for the Cryptococcus neoformans-Cryptococcus gattii species complex using the CLSI M27-A3 broth microdilution method

Cryptococcosis-a systematic review to inform the World Health Organization Fungal Priority Pathogens List

Cryptococcosis causes a high burden of disease worldwide. This systematic review summarizes the literature on Cryptococcus neoformans and C. gattii infections to inform the World Health Organization's first Fungal Priority Pathogen List. PubMed and Web of Science were used to identify studies reporting on annual incidence, mortality, morbidity, antifungal resistance, preventability, and distribution/emergence in the past 10 years. Mortality rates due to C. neoformans were 41%-61%. Complications included acute renal impairment, raised intracranial pressure needing shunts, and blindness. There was moderate evidence of reduced susceptibility (MIC range 16-32 mg/l) of C. neoformans to fluconazole, itraconazole, ketoconazole, voriconazole, and amphotericin B. Cryptococcus gattii infections comprised 11%-33% of all cases of invasive cryptococcosis globally. The mortality rates were 10%-23% for central nervous system (CNS) and pulmonary infections, and ∼43% for bloodstream infections. Complications described included neurological sequelae (17%-27% in C. gattii infections) and immune reconstitution inflammatory syndrome. MICs were generally low for amphotericin B (MICs: 0.25-0.5 mg/l), 5-flucytosine (MIC range: 0.5-2 mg/l), itraconazole, posaconazole, and voriconazole (MIC range: 0.06-0.5 mg/l). There is a need for increased surveillance of disease phenotype and outcome, long-term disability, and drug susceptibility to inform robust estimates of disease burden.

Minimum inhibitory concentrations of antifungals against invasive isolates of Cryptococcus species worldwide: Global antifungal antimicrobial testing leadership and surveillance program, 2010-2020

This study examined the geographic distribution of minimum inhibitory concentrations (MICs) of antifungals against Cryptococcus isolates. Data were collected on the MICs of specific antifungals (amphotericin B, 5-flucytosine, fluconazole, voriconazole, posaconazole, and isavuconazole) against various Cryptococcus species for the period 2010 to 2020 from the Antimicrobial Testing Leadership and Surveillance database. Cryptococcus isolates were collected from samples of blood and cerebrospinal fluid (CSF) from patients hospitalized in different regions worldwide. We applied the epidemiological cutoff values (ECVs) of antifungals against various Cryptococcus species to distinguish wild-type (WT) from non-WT Cryptococcus isolates. A total of 395 isolates of Cryptococcus species cultured from blood (n = 201) or CSF (n = 194) were analyzed. C. grubii (n = 270), C. neoformans (n = 111), and C. gattii (n = 11) were the three predominant species causing bloodstream infections (BSI) or meningitis/meningoencephalitis (MME). The proportion of MICs above the ECV (1 mg/L) for amphotericin B among C. neoformans isolates was significantly lower than that among C. gattii isolates (MICs >0.5 mg/L; P < 0.001), as evaluated using the chi-square test. For most isolates of the three predominant Cryptococcus species, the MICs of new triazoles were ≤0.25 mg/L. The MICs of fluconazole and amphotericin B in the BSI/MME-causing Cryptococcus isolates collected from patients hospitalized in the Asia-Western Pacific region and Europe were significantly lower (i.e., the distributions were more leftward) than those in North America and Latin America. Ongoing monitoring of MIC data for important antifungals against cryptococcosis is crucial.

Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Isavuconazonium Sulfate

A Biopharmaceutics Classification System (BCS)-based biowaiver monograph is presented for isavuconazonium sulfate. A BCS-based biowaiver is a regulatory option to substitute appropriate in vitro data for in vivo bioequivalence studies. Isavuconazonium sulfate is the prodrug of isavuconazole, a broad-spectrum azole antifungal indicated for invasive fungal infections. While the prodrug can be classified as a BCS Class III drug with high solubility but low permeability, the parent drug can be classified as a BCS Class II drug with low solubility but high permeability. Interestingly, the in vivo behavior of both is additive and leads isavuconazonium sulfate to act like a BCS class I drug substance after oral administration. In this work, experimental solubility and dissolution data were evaluated and compared with available literature data to investigate whether it is feasible to approve immediate release solid oral dosage forms containing isavuconazonium sulfate according to official guidance from the FDA, EMA and/or ICH. The risks associated with waiving a prodrug according to the BCS-based biowaiver guidelines are reviewed and discussed, noting that current regulations are quite restrictive on this point. Further, results show high solubility but instability of isavuconazonium sulfate in aqueous media. Although experiments on the dissolution of the capsule contents confirmed 'very rapid' dissolution of the active pharmaceutical ingredient (API) isavuconazonium sulfate, its release from the commercial marketed capsule formulation Cresemba is limited by the choice of capsule shell material, providing an additional impediment to approval of generic versions via the BCS-Biowaiver approach.

In vitro isavuconazole activity against Sporothrix brasiliensis suggests its efficacy in some severe sporotrichosis cases

Background: Sporothrix brasiliensis causes sporotrichosis, an important infection in some groups of patients. Aims: This work was designed to investigate the effects of isavuconazole against this species. Methods: An antifungal susceptibility test was performed to compare MIC values with other antifungal drugs used to treat sporotrichosis. A checkerboard assay was performed to understand isavuconazole interactions. Furthermore, isavuconazole growth inhibition on an itraconazole-resistant strain was tested. Results: Isavuconazole had similar MICs to other azoles against S. brasiliensis, presenting fungistatic activity. Isavuconazole did not interact in vitro with antifungals or immunosuppressive drugs and inhibited the growth of an itraconazole-resistant strain. Conclusion: Isavuconazole inhibits S. brasiliensis, its pharmacologic characteristics make it a candidate for patients with sporotrichosis and it may be useful to combat sporotrichosis caused by resistant isolates.

A systematic review and meta-analysis of efficacy and safety of isavuconazole for the treatment and prophylaxis of invasive fungal infections

BACKGROUND

Isavuconazole is a novel triazole antifungal agent. However, the previous outcomes were highlighted by statistical heterogeneity. This meta-analysis aimed to validate the efficacy and safety of isavuconazole for the treatment and prophylaxis of invasive fungal infections (IFIs) compared with other antifungal agents (amphotericin B, voriconazole and posaconazole).

METHODS

Scopus, EMBASE, PubMed, CINAHL and Ichushi databases were searched for relevant articles that met the inclusion criteria through February 2023. Mortality, IFI rate, discontinuation rate of antifungal therapy and incidence of abnormal hepatic function were evaluated. The discontinuation rate was defined as the percentage of therapy discontinuations due to adverse events. The control group included patients who received other antifungal agents.

RESULTS

Of the 1784 citations identified for screening, 10 studies with an overall total of 3037 patients enrolled. Isavuconazole was comparable with the control group in mortality and IFI rate in the treatment and prophylaxis of IFIs, respectively (mortality, odds rate (OR) 1.11, 95% confidential interval (CI) 0.82-1.51; IFI rate, OR 1.02, 95% CI 0.49-2.12). Isavuconazole significantly reduced the discontinuation rate in the treatment (OR 1.96, 95% CI 1.26-3.07) and incidence of hepatic function abnormalities in the treatment and prophylaxis, compared with the control group (treatment, OR 2.31, 95% CI 1.41-3.78; prophylaxis, OR 3.63, 95% CI 1.31-10.05).

CONCLUSIONS

Our meta-analysis revealed that isavuconazole was not inferior to other antifungal agents for the treatment and prophylaxis of IFIs, with substantially fewer drug-associated adverse events and discontinuations. Our findings support the use of isavuconazole as the primary treatment and prophylaxis for IFIs.

Exposure of Cryptococcus neoformans to Seven Commonly Used Agricultural Azole Fungicides Induces Resistance to Fluconazole as Well as Cross-Resistance to Voriconazole, Posaconazole, Itraconazole and Isavuconazole

BACKGROUND

Cross-resistance to medical azoles by exposure to azole pesticides is well documented for Aspergillus family fungi but is poorly evaluated for other environmental pathogen fungi, particularly for yeasts belonging to the Cryptococcus neoformans/Cryptococcus gattii species complexes.

METHODS

One thousand C. neoformans yeast were exposed to various concentrations of seven different commonly used azole pesticides. Clones surviving exposure were picked randomly, and their minimal inhibitory concentrations (MICs) of fluconazole, voriconazole, posaconazole, itraconazole and isavuconazole were assessed.

RESULTS

Depending on the pesticide used for exposure, up to 13.3% of selected Cryptococcus colonies showed a phenotype of resistance to fluconazole, and among them, several showed cross-resistance to another or several other medical azoles. Molecular mechanisms involved in the resistance setups seem to be dependent on ERG11 and AFR1 gene overexpression.

CONCLUSION

Exposure to any of the seven azole pesticides tested is capable of increasing the MIC of fluconazole in C. neoformans, including up to the level of the fluconazole-resistant phenotype, as well as generating cross-resistance to other medical azoles in some cases.

False-negative cerebral spinal fluid cryptococcal antigen lateral flow assay due to postzone phenomenon in a patient with disseminated cryptococcal disease: a case report

This report presents the case of false-negative cerebral spinal fluid (CSF) cryptococcal antigen (CrAg) lateral flow assay (LFA) in a HIV-positive 25-year-old male. The patient presented with headache, nausea and vomiting for 5 days and syncope for 1 day. An initial CSF CrAg LFA test was negative, but a 1:4 dilution of the CSF was weakly positive and a 1:8 dilution was positive. A serum cryptococcal antigen test was weakly positive. Cultures of blood and CSF were all positive for Cryptococcus neoformans. The explanation for the false-negative CSF CrAg LFA test is that the antigen concentration was too high causing the postzone phenomenon.

New Perspectives on Antimicrobial Agents: Isavuconazole

Isavuconazole is the newest of the clinically available advanced generation triazole antifungals and is active against a variety of yeasts, molds, and dimorphic fungi. Its current FDA-approved indications include the management of invasive aspergillosis as well as mucormycosis, though the latter indication is supported by limited clinical data. Isavuconazole did not achieve noninferiority to caspofungin for the treatment of invasive candidiasis and therefore lacks an FDA-approved indication for this invasive disease. Significant advantages of isavuconazole, primarily over voriconazole but in some circumstances posaconazole as well, make it an appealing option for the management of complex patients with invasive fungal infections. These potential advantages include lack of QTc interval prolongation, more predictable pharmacokinetics, a less complicated drug interaction profile, and improved tolerability, particularly when compared to voriconazole. This review discusses these topics in addition to addressing the in vitro activity of the compound against a variety of fungi and provides insight into other distinguishing factors among isavuconazole, voriconazole, and posaconazole. The review concludes with an opinion section in which the authors provide the reader with a framework for the current role of isavuconazole in the antifungal armamentarium and where further data are required.

Pharmacokinetics of isavuconazole in healthy cats after oral and intravenous administration

Background

Isavuconazole is a triazole antifungal drug that has shown good efficacy in human patients. Absorption and pharmacokinetics have not been evaluated in cats.

Objectives

To determine the pharmacokinetics of isavuconazole in cats given a single IV or PO dose.

Animals

Eight healthy, adult research cats.

Methods

Four cats received 100 mg capsules of isavuconazole PO. Four cats received 5 mg/kg isavuconazole solution IV. Serum was collected at predetermined intervals for analysis using ultra‐high performance liquid chromatography‐tandem mass spectrometry. Data were analyzed using a 2‐compartment uniform weighting pharmacokinetic analysis with lag time for PO administration and a 2 compartment, 1/y² weighting for IV administration. Predicted 24 and 48‐hour dosing intervals of 100 mg isavuconazole administered PO were modeled and in vitro plasma protein binding was assessed.

Results

Both PO and IV drug administration resulted in high serum concentrations. Intravenous and PO formulations of isavuconazole appear to be able to be used interchangeably. Peak serum isavuconazole concentrations occurred 5 ± 3.8 hours after PO administration with an elimination rate half‐life of 66.2 ± 55.3 hours. Intersubject variability was apparent in both the PO and IV groups. Two cats vomited 6 to 8 hours after PO administration. No adverse effects were observed in the IV group. Oral bioavailability was estimated to be approximately 88%. Serum protein binding was calculated to be approximately 99.0% ± 0.03%.

Conclusions and Clinical Importance

Isavuconazole might prove to be useful in cats with fungal disease given its favorable pharmacokinetics. Additional studies on safety, efficacy, and tolerability of long‐term isavuconazole use are needed.

Prevalence, Genetic Structure, and Antifungal Susceptibility of the Cryptococcus neoformans/C. gattii Species Complex Strains Collected from the Arboreal Niche in Poland

Fungi belonging to the Cryptococcus neoformans/C. gattii species complex (CNGSC) are etiological agents of serious and not infrequently fatal infections in both humans and animals. Trees are the main ecological niche and source of potential exposition concerning these pathogens. With regard to epidemiology of cryptococcosis, various surveys were performed worldwide, enabling the establishment of a map of distribution and genetic structure of the arboreal population of the CNGSC. However, there are regions, among them Central and Eastern Europe, in which the data are lacking. The present study shows the results of such an environmental study performed in Wrocław, Poland. The CNGSC strains were detected in 2.2% of the tested trees belonging to four genera. The obtained pathogen population consisted exclusively of C. neoformans, represented by both the major molecular type VNI and VNIV. Within the tested group of isolates, resistance to commonly used antimycotics was not found, except for 5-fluorocytosine, in which about 5% of the strains were classified as a non-wild type.

In vitro Antifungal Susceptibility Profiles of Cryptococcus neoformans var. grubii and Cryptococcus gattii Clinical Isolates in Guangxi, Southern China

This study analyzed the in vitro drug sensitivity of Cryptococcus spp. from Guangxi, Southern China. One hundred three strains of Cryptococcus were recovered from 86 patients; 14 were HIV positive and 72 were HIV negative. Ninety-two strains were identified as Cryptococcus neoformans var. grubii, while 11 strains were identified as Cryptococcus gattii (5 C. gattii sensu stricto and 6 Cryptococcus deuterogattii). The recovered strains were tested against commonly used antifungal drugs (fluconazole, amphotericin B, 5-fluorocytosine, itraconazole, and voriconazole) and to novel antifungal drugs (posaconazole and isavuconazole) using CLSI M27-A4 method. The results showed that all isolates were susceptible to most antifungal drugs, of which the minimum inhibitory concentration (MIC) ranges were as follows: 0.05-4 μg/ml for fluconazole, 0.25-1 μg/ml for amphotericin B; 0.0625-2 μg/ml for 5-fluorocytosine, 0.0625-0.25 μg/ml for itraconazole, 0.0078-0.25 μg/ml for voriconazole, 0.0313-0.5 μg/ml for posaconazole, 0.0020-0.125 μg/ml for isavuconazole for C. neoformans var. grubii isolates, and 1-16 μg/ml for fluconazole, 0.125-1 μg/ml for 5-fluorocytosine, 0.25-1 μg/ml for amphotericin B, 0.0625-0.25 μg/ml for itraconazole, 0.0156-0.125 μg/ml for voriconazole, 0.0156-0.25 μg/ml for posaconazole, and 0.0078-0.125 μg/ml for isavuconazole for C. gattii isolates. Furthermore, some C. neoformans var. grubii isolates were found to be susceptible-dose dependent to 5-fluorocytosine and itraconazole. In addition, a reduction in the potency of fluconazole against C. gattii is possible. We observed no statistical differences in susceptibility of C. neoformans var. grubii and C. gattii in the tested strains. Continuous observation of antifungal susceptibility of Cryptococcus isolates is recommended to monitor the emergence of resistant strains.

Successful Isavuconazole Salvage Therapy for a Cryptococcus deuterogattii (AFLP6/VGII) Disseminated Infection in a European Immunocompetent Patient

Members of the Cryptococcus gattii species complex are notorious causes of cryptococcosis as they often cause severe, life-threatening infections. Here we describe a case of a severe disseminated C. deuterogattii infection in a previously healthy patient who was initially treated with amphotericin B, 5-fluorocytosine and fluconazole, which led to a good neurological response, but the infection in the lungs remained unaltered and was not completely resolved until switching the antifungal therapy to isavuconazole. The infection was likely acquired during a one-month stay at the Azores Islands, Portugal. Environmental sampling did not yield any cryptococcal isolate; therefore, the source of this apparent autochthonous case could not be determined. Molecular typing showed that the cultured C. deuterogattii isolates were closely related to the Vancouver Island outbreak-genotype.

An analysis of the population of Cryptococcus neoformans strains isolated from animals in Poland, in the years 2015-2019

Fungi belonging to the Cryptococcus neoformans/C. gattii species complex (CNGSC) are pathogens causing severe infections in humans and animals, that for humans may result in a mortality rate ranging up to 70%. The CNGSC is divided into eight major molecular types, that may differ in their virulence and susceptibility. In order to fully understand the epidemiology of cryptococcosis, it is important to study the world distribution and population structure of these pathogens. The present study is the first presenting a population of strains isolated in Poland and one of the few using a multi-species animal group as a source of the specimen. The pathogen was present in 2.375% of the tested animals. The URA5-RFLP and MALDI-TOF MS analyses have revealed that the population consisted exclusively of C. neoformans strains, with a predominance of major molecular type VNIV (C. neoformans var. neoformans). The MALDI-TOF MS was used to perform the CNGSC strains identification on both the species and sub-species level. Despite the fact that the animals providing the specimens were not treated with 5-fluorocytosine, around 10% of the tested population presented MIC values exceeding 64 mg/L, indicating the existence of the 5-fluorocytosine-resistant strains in the environment.

Molecular Markers of Antifungal Resistance: Potential Uses in Routine Practice and Future Perspectives

Antifungal susceptibility testing (AST) has come to establish itself as a mandatory routine in clinical practice. At the same time, the mycological diagnosis seems to have headed in the direction of non-culture-based methodologies. The downside of these developments is that the strains that cause these infections are not able to be studied for their sensitivity to antifungals. Therefore, at present, the mycological diagnosis is correctly based on laboratory evidence, but the antifungal treatment is undergoing a growing tendency to revert back to being empirical, as it was in the last century. One of the explored options to circumvent these problems is to couple non-cultured based diagnostics with molecular-based detection of intrinsically resistant organisms and the identification of molecular mechanisms of resistance (secondary resistance). The aim of this work is to review the available molecular tools for antifungal resistance detection, their limitations, and their advantages. A comprehensive description of commercially available and in-house methods is included. In addition, gaps in the development of these molecular technologies are discussed.

Clinical experience with isavuconazole in healthy volunteers and patients with invasive aspergillosis in China, and the results from an exposure-response analysis

BACKGROUND

Isavuconazole is a broad-spectrum triazole for the treatment of invasive fungal disease (IFD).

OBJECTIVE

To investigate the clinical experience with isavuconazole in Chinese individuals.

PATIENTS/METHODS

Participants were Chinese healthy volunteers from a Phase I pharmacokinetics (PK) and safety study of single/multiple doses of isavuconazole (n = 36) and Chinese patients from the global Phase III SECURE study that assessed safety and efficacy of isavuconazole vs voriconazole for IFD treatment (n = 26).

RESULTS

No clinically relevant differences in PK were found between Chinese and Western participants, although exposure was increased in Chinese volunteers. Treatment-emergent adverse events (TEAEs) were reported in 75.0% of healthy volunteers, many of which were infusion-related. No serious AEs were reported. In SECURE, findings in Chinese patients (n = 26) were similar to the global population. For patients who received ≥1 dose of study drug, allcause mortality from first dose to Day 42 was 10.0% (1/10) with isavuconazole and 25.0% (4/16) with voriconazole (treatment difference [95% confidence interval, CI]: -15.0% [-43.2%, 13.2%]). Overall response at the end of treatment for patients with proven/probable IFD was 25.0% and 16.7% with isavuconazole and voriconazole, respectively (treatment difference [95% CI] -8.3% [-60.2%, 43.5%]). Isavuconazole was associated with lower incidence of hepatobiliary, eye, skin, subcutaneous tissue and psychiatric disorders compared with voriconazole and lower incidence of treatment-related TEAEs, serious TEAES or death overall.

CONCLUSIONS

Although further research is required, this study demonstrated a favourable risk-benefit profile of isavuconazole in Chinese patients.

Isavuconazole: Mechanism of Action, Clinical Efficacy, and Resistance

Increasing incidence of invasive fungal infections combined with a growing population of immunocompromised hosts has created a rising need for antifungal agents. Isavuconazole, a second-generation broad-spectrum triazole with activity against yeasts, dimorphic fungi, and molds, has a favorable safety profile and predictable pharmacokinetics. Patients typically tolerate isavuconazole well with fewer drug-drug interactions. Clinical trials have found it to be noninferior to voriconazole for invasive aspergillosis, an alternative therapy for salvage treatment of mucormycosis, and suitable for stepdown therapy with invasive candidiasis. Cross-resistance with other triazoles is common. More studies are needed to determine the role of isavuconazole in anti-mold prophylaxis in high-risk patients.

False-Negative Serum Cryptococcal Antigen Lateral Flow Immunoassay Result for a Patient with Disseminated Cryptococcal Disease

Cryptococcus neoformans (C. neoformans) is an opportunistic fungal pathogen to humans, which can be acquired from environmental sources. Its most important virulence factor is its polysaccharide capsule, which can be used for diagnostic tests that identify the cryptococcal antigen (CrAg). The CrAg lateral flow assay (LFA) is a dipstick immunochromatographic assay with high sensitivity and specificity; however, several false-negative cases have been reported. Here, we present a case of a false-negative serum CrAg LFA, in which the blood culture from a matched sample was positive for C. neoformans, thus demonstrating the postzone phenomenon.

Emerging Cryptococcus gattii species complex infections in Guangxi, southern China

The emergence and spread of cryptococcosis caused by the Cryptococcus gattii species complex has become a major public concern worldwide. C. deuterogattii (VGIIa) outbreaks in the Pacific Northwest region demonstrate the expansion of this fungal infection to temperate climate regions. However, infections due to the C. gattii species complex in China have rarely been reported. In this study, we studied eleven clinical strains of the C. gattii species complex isolated from Guangxi, southern China. The genetic identity and variability of these isolates were analyzed via multi-locus sequence typing (MLST), and the phylogenetic relationships among these isolates and global isolates were evaluated. The mating type, physiological features and antifungal susceptibilities of these isolates were also characterized. Among the eleven isolates, six belonged to C. deuterogattii, while five belonged to C. gattii sensu stricto. The C. deuterogattii strains from Guangxi, southern China were genetically variable and clustered with different clinical isolates from Brazil. All strains were MATα, and three C. deuterogattii isolates (GX0104, GX0105 and GX0147) were able to undergo sexual reproduction. Moreover, most strains had capsule and were capable of melanin production when compared to the outbreak strain from Canada. Most isolates were susceptible to antifungal drugs; yet one of eleven immunocompetent patients died of cryptococcal meningitis caused by C. deuterogattii (GX0147). Our study indicated that the highly pathogenic C. deuterogattii may be emerging in southern China, and effective nationwide surveillance of C. gattii species complex infection is necessary.

Cryptococcosis is a fatal systemic fungal disease caused by Cryptococcus neoformans/gattii species complexes. As a former member of the C. neoformans, C. gattii had been easily neglected before being elevated to species level. Human C. gattii species complex infection was previously confined to the tropical and subtropical regions worldwide. However, in 1999, an outbreak of C. gattii species complex occurred on Vancouver Island in Canada then expanded to the Pacific Northwest in the USA, causing over 200 infections. The highly virulent, highly pathogenic and more resistant to antifungal drugs of this species have become a therapeutic problem. To initiate a better understanding of the infection characteristics and pathogenicity of C. gattii species complex in Guangxi, southern China, the current study aimed to characterize the C. gattii species complex isolates genetically and phenotypically. The ISHAM consensus MLST scheme was utilized to investigate the genetic structure of C. gattii species complex and to correlate their geographic origin, clinical source, virulence factors and antifungal susceptibility. The authors expect that this work can support surveillance and encourage more research and public health initiatives to prevent and control the cryptococcosis cause by C. gattii species complex.

Genotypic diversity in clinical and environmental isolates of Cryptococcus neoformans from India using multilocus microsatellite and multilocus sequence typing

BACKGROUND

Cryptococcus neoformans is the leading cause of cryptococcal meningitis in HIV/AIDS patients. As infections in humans are predominantly caused by the inhalation of basidiospores from environmental sources, therefore, analysing the population structure of both clinical and environmental populations of C neoformans can increase our understanding of the molecular epidemiology of cryptococcosis.

OBJECTIVE

To investigate the genotypic diversity and antifungal susceptibility profile of a large collection of C neoformans isolates (n = 523) from clinical and environmental sources in India between 2001 and 2014.

MATERIALS AND METHODS

Cryptococcus neoformans isolates were genotyped by AFLP, microsatellite typing (MLMT) and MLST. In vitro antifungal susceptibility for standard antifungals was undertaken using CLSI M27-A3.

RESULTS

All isolates were C neoformans, AFLP1/VNI and exhibited mating-type MATα. MLMT revealed that the majority of isolates belonged to microsatellite cluster (MC) MC3 (49%), followed by MC1 (35%), and the remaining isolates fell in 11 other MC types. Interestingly, two-thirds of clinical isolates were genotype MC3 and only 17% of them were MC1, whereas majority of environmental strains were MC1 (54%) followed by MC3 (16%). Overall, MLST assigned 5 sequence types (STs) among all isolates and ST93 was the most common (n = 76.7%), which was equally distributed in both HIV-positive and HIV-negative patients. Geometric mean MICs revealed that isolates in MC1 were significantly less (P < .05) susceptible to amphotericin B, 5-flucytosine, itraconazole, posaconazole and isavuconazole than isolates in MC3.

CONCLUSIONS

The study shows a good correlation between MLMT and MLST genotyping methods. Further, environmental isolates were genetically more diverse than clinical isolates.

Corticosteroids for Posttransplant Immune Reconstitution Syndrome in Cryptococcus gattii Meningoencephalitis: Case Report and Literature Review

Cryptococcus gattii represents an emerging fungal pathogen of immunocompromised and immunocompetent hosts in the United States. To our knowledge, this is the first case of posttransplant immune reconstitution syndrome due to C. gattii meningoencephalitis successfully treated with corticosteroids. We also report successful maintenance phase treatment with isavuconazole, a novel triazole, following fluconazole-induced prolonged QT syndrome.

Treatment Failure of Isavuconazole in a Patient with Cryptococcosis

Isavuconazole is a broad-spectrum azole that is FDA-approved for the treatment of aspergillosis and mucormycosis; data on the use of isavuconazole for the treatment and prevention of other invasive fungal infections are limited. Here, we report a patient with pulmonary cryptococcosis treated with isavuconazole who experienced progression to disseminated infection with Cryptococcus while on isavuconazole. Caution is advised when using isavuconazole in situations where there is a paucity of data to recommend its use.

Pharmacodynamics of Isavuconazole in a Rabbit Model of Cryptococcal Meningoencephalitis

Cryptococcus spp., important fungal pathogens, are the leading cause of fungus-related mortality in human immunodeficiency virus-infected patients, and new therapeutic options are desperately needed. Isavuconazonium sulfate, a newer triazole antifungal agent, was studied to characterize the exposure-response relationship in a rabbit model of cryptococcal meningoencephalitis. Rabbits treated with isavuconazonium sulfate were compared with those treated with fluconazole and untreated controls. The fungal burden in the cerebrospinal fluid was measured serially over time, while the yeast concentrations in the brain and the eye (aqueous humor) were determined at the end of therapy. The exposure impact of isavuconazonium sulfate dosing in the rabbit was linked using mathematical modeling. Similar significant reductions in the fungal burden in the brain and cerebrospinal fluid in rabbits treated with isavuconazonium sulfate and fluconazole compared with that in the untreated controls were observed. No dose-dependent response was demonstrated with isavuconazonium sulfate treatment in this study. The treatment of cryptococcal meningoencephalitis with isavuconazonium sulfate was similar to that with fluconazole. Dose-dependent reductions in yeast over time were not demonstrated, which limited our ability to estimate the pharmacodynamic target. Further nonclinical and clinical studies are needed in order to characterize the extent of the exposure-response relationship in cryptococcal meningoencephalitis. However, this study suggests that isavuconazonium sulfate, like fluconazole, could be beneficial in the setting of consolidation and maintenance therapy, rather than induction monotherapy, in high-burden cryptococcal meningoencephalitis.

Genotypic diversity and antifungal susceptibility of Cryptococcus neoformans isolates from paediatric patients in China

Cryptococcosis is a life-threatening mycosis primarily occurring in adult patients particularly those with immunosuppression such as HIV infection/AIDS. The number of reported cases of paediatric cryptococcosis has increased in the last decade around the world, including China. However, current information on the characteristics of cryptococcosis in children, particularly the genotypic diversity and antifungal susceptibility of the isolates, is limited. In the present study, a total of 25 paediatric isolates of Cryptococcus neoformans were genotyped using the ISHAM-MLST scheme. In vitro susceptibility to antifungal agents of the 22 isolates was tested using the CLSI M27-A3 method. Our analyses revealed that the genotypic diversity of C. neoformans isolates from Chinese paediatric patients was low, with ST 5 (80%) and ST 31 (12%) being the two major sequence types. Reduced susceptibility to fluconazole (FLU), 5-flucytosine (5-FC) and itraconazole (ITR) was observed among C. neoformans isolates from Chinese paediatric patients, particularly among the ST5 isolates, which was similar to observations made on C. neoformans isolates from Chinese adult patients. In addition, the majority of isolates (3/4, 75%) obtained from deceased patients showed decreased antifungal susceptibility, which indicates that further monitoring of antifungal susceptibility of Cryptococcus isolates is warranted in management of paediatric cryptococcosis.

Direct in vitro comparison of the prodrug isavuconazonium sulfate with the isavuconazole active compound against Aspergillus spp. and 2 rare moulds

Isavuconazonium sulfate is a prodrug of isavuconazole, a broad-spectrum mould-active triazole antifungal drug. We provide a direct comparison of the in vitro activity of the prodrug versus the active metabolite against clinical isolates of Aspergillus spp., Sarocladium kiliense, and Scedosporium apiospermum using CLSI broth microdilution methods. The MIC values obtained for the prodrug were one 2-fold dilution higher than those of isavuconazole for all isolates tested. Using previously defined epidemiological cutoff values for isavuconazole and Aspergillus spp., 96.4% of isolates were wild type (WT) to isavuconazole and only 75% were WT to the prodrug. The essential agreement (±2 log₂ dilutions) between prodrug and isavuconazole MIC values was 96.4% across all tested isolates. The active metabolite, isavuconazole, is recommended to use during in vitro susceptibility testing of fungal isolates.

Molecular characterization and antifungal susceptibility testing of Cryptococcus neoformans sensu stricto from southern Brazil

PURPOSE

Cryptococcosis is acquired from the environment by the inhalation of Cryptococcus cells and may establish from an asymptomatic latent infection into pneumonia or meningoencephalitis. The genetic diversity of a Cryptococcus neoformans species complex has been investigated by several molecular tools, such as multi-locus sequence typing, amplified fragment length polymorphism (AFLP), restriction fragment length polymorphism and microsatellite analysis. This study aimed to investigate the genotype distributions and antifungal susceptibility profiles of C. neoformans sensu lato isolates from southern Brazil.

METHODOLOGY

We studied 219 C. neoformans sensu lato isolates with mating- and serotyping, AFLP fingerprinting, microsatellite typing and antifungal susceptibility testing.Results/Key findings. Among the isolates, 136 (69 %) were from HIV-positive patients. Only C. neoformans mating-type α and serotype A were observed. AFLP fingerprinting analysis divided the isolates into AFLP1/VNI (n=172; 78.5 %), AFLP1A/VNII (n=19; 8.7 %), AFLP1B/VNII (n=4; 1.8 %) and a new AFLP pattern AFLP1C (n=23; 10.5 %). All isolates were susceptible to tested antifungals and no correlation between antifungal susceptibility and genotypes was observed. Through microsatellite analysis, most isolates clustered in a major microsatellite complex and Simpson's diversity index of this population was D=0.9856.

CONCLUSION

The majority of C. neoformans sensu stricto infections occurred in HIV-positive patients. C. neoformans AFLP1/VNI was the most frequent genotype and all antifungal drugs had high in vitro activity against this species. Microsatellite analyses showed a high genetic diversity within the regional C. neoformans sensu stricto population, and correlation between environmental and clinical isolates, as well as a temporal and geographic relationship.

Antifungals discovery: an insight into new strategies to combat antifungal resistance

Undeniably, new antifungal treatments are necessary against pathogenic fungi. Fungal infections have significantly increased in recent decades, being highlighted as important causes of morbidity and mortality, particularly in immunocompromised patients. Five main antifungal classes are used: (i) azoles, (ii) echinocandins, (iii) polyenes, (iv) allylamines and (v) pyrimidine analogues. Moreover, the treatment of mycoses has several limitations, such as undesirable side effects, narrow activity spectrum, a small number of targets and fungal resistance, which are still of major concern in clinical practice. The discovery of new antifungals is mostly achieved by the screening of natural or synthetic/semisynthetic chemical compounds. The most recent discoveries in drug resistance mechanism and their avoidance were explored in a review, focusing on different antifungal targets, as well as new agents or strategies, such as combination therapy, that could improve antifungal therapy.

SIGNIFICANCE AND IMPACT OF THE STUDY

The failure to respond to antifungal therapy is complex and is associated with microbiological resistance and increased expression of virulence in fungal pathogens. Thus, this review offers an overview of current challenges in the treatment of fungal infections associated with increased antifungal drug resistance and the formation of biofilms in these opportunistic pathogens. Furthermore, the most recent and potential strategies to combat fungal pathogens are explored here, focusing on new agents as well as innovative approaches, such as combination therapy between antifungal drugs or with natural compounds.

Exploration of Antifungal and Immunomodulatory Potentials of a Furanone Derivative to Rescue Disseminated Cryptococosis in Mice

Cryptococcus neoformans infection is quite complex with both host-pathogen interaction and host immune profile determining disease progress and therapeutic outcome. Hence in the present study, the potential utility of (E)-5-benzylidenedihydrofuran-2(3 H)-one (compound-6) was explored as an effective anticryptococcal compound with immunomodulatory potential. The efficacy of compound-6 in pulmonary cryptococosis model using H99 strain was investigated. The effective dose was found to provide 100% survival, with a significant reduction of yeast burden in lungs and brain. The biodistribution analysis provided evidence for the presence of higher concentration of compound-6 in major organs including lungs and brain. In addition, compound-6 treated mice had significantly higher expression of IL-6, IL-4 and IFN-γ in lung and brain. Similarly, elevated expression of TNF-α, IL-β1 and IL-12 were observed in lungs, suggesting the protective host response against C. neoformans. The reduction and clearance of fungal load in systemic organs and mouse survival are notable results to confirm the ability of compound-6 to treat cryptococcosis. In conclusion, the low molecular weight (174 Da), lipophilicity, its ability to cross blood brain barrier, and facilitating modulation of cytokine expression are the added advantages of compound-6 to combat against disseminated cryptococosis.

Ecoepidemiology of Cryptococcus gattii in Developing Countries

Cryptococcosis is a systemic infection caused by species of the encapsulated yeast Cryptococcus. The disease may occur in immunocompromised and immunocompetent hosts and is acquired by the inhalation of infectious propagules present in the environment. Cryptococcus is distributed in a plethora of ecological niches, such as soil, pigeon droppings, and tree hollows, and each year new reservoirs are discovered, which helps researchers to better understand the epidemiology of the disease. In this review, we describe the ecoepidemiology of the C. gattii species complex focusing on clinical cases and ecological reservoirs in developing countries from different continents. We also discuss some important aspects related to the antifungal susceptibility of different species within the C. gattii species complex and bring new insights on the revised Cryptococcus taxonomy.

Combination Therapy with Isavuconazole and Micafungin for Treatment of Experimental Invasive Pulmonary Aspergillosis

Invasive pulmonary aspergillosis (IPA) is an important cause of morbidity and mortality in immunocompromised patients. We hypothesized that simultaneous inhibition of biosynthesis of ergosterol in the fungal cell membrane and (1→3)-β-d-glucan in the cell wall, respectively, by the antifungal triazole isavuconazole (ISA) and the echinocandin micafungin (MFG) may result in improved outcomes in experimental IPA in persistently neutropenic rabbits. Treatments included ISA at 20 mg/kg of body weight/day (ISA20), 40 mg/kg/day (ISA40), and 60 mg/kg/day (ISA60); MFG at 2 mg/kg/day (MFG2); combinations of ISA20 and MFG2, ISA40 and MFG2, and ISA60 and MFG2; and no treatment (untreated controls [UC]). The galactomannan index (GMI) and (1→3)-β-d-glucan levels in serum were measured. The residual fungal burden (number of CFU per gram) was significantly reduced in ISA20-, ISA40-, ISA60-, ISA20-MFG2-, ISA40-MFG2-, and ISA60-MFG2-treated rabbits compared with that in MFG2-treated or UC rabbits (P < 0.01). Measures of organism-mediated pulmonary injury, lung weights, and pulmonary infarct score were lower in ISA40-MFG2-treated rabbits than in rabbits treated with ISA40 or MFG2 alone (P < 0.01). Survival was prolonged in ISA40-MFG2-treated rabbits in comparison to those treated with ISA40 or MFG2 alone (P < 0.01). These outcome variables correlated directly with significant declines in GMI and serum (1→3)-β-d-glucan levels during therapy. The GMI correlated with measures of organism-mediated pulmonary injury, lung weights (r = 0.764; P < 0.001), and pulmonary infarct score (r = 0.911; P < 0.001). In summary, rabbits receiving combination therapy with isavuconazole and micafungin demonstrated a significant dose-dependent reduction in the residual fungal burden, decreased pulmonary injury, prolonged survival, a lower GMI, and lower serum (1→3)-β-d-glucan levels in comparison to rabbits receiving isavuconazole or micafungin as a single agent.

Establishment and Use of Epidemiological Cutoff Values for Molds and Yeasts by Use of the Clinical and Laboratory Standards Institute M57 Standard

Breakpoints are used to predict whether an antifungal agent will be clinically effective against a particular fungal isolate. They are based on a combination of MIC values, pharmacokinetic/pharmacodynamic values, and clinical outcome data. For many fungus-antifungal combinations, these data might never be available. For these combinations, epidemiological cutoff values (ECVs) provide a methodology for categorizing isolates as either wild type (WT) or non-WT. In this review, we define ECVs, explain how they are generated using the CLSI methodology in standard M57, and describe how they can be used in clinical practice.

Isavuconazole Is Effective for the Treatment of Experimental Cryptococcal Meningitis

We evaluated the efficacy of isavuconazole against cryptococcal meningitis. Treatment with either oral isavuconazole (120 mg/kg and 240 mg/kg twice a day [BID]) or fluconazole as the positive control significantly improved survival in mice infected intracranially with either Cryptococcus neoformans USC1597 or H99 and significantly reduced brain fungal burdens for both isolates. Concentrations of isavuconazole in plasma and brain tissue also demonstrated that the greatest improvements in survival and fungal burden were associated with elevated exposures.

In vitro antifungal susceptibility profiles of Cryptococcus species isolated from HIV-associated cryptococcal meningitis patients in Zimbabwe

Cryptococcus neoformans is the leading cause of cryptococcosis in HIV-infected subjects worldwide. Treatment of cryptococcosis is based on amphotericin B, flucytosine, and fluconazole. In Zimbabwe, little is known about antifungal susceptibility of Cryptococcus. Sixty-eight genotyped Cryptococcus isolates were tested for antifungal profiles. Amphotericin B, isavuconazole, and voriconazole showed higher activity than other triazoles. Fluconazole and flucytosine were less effective, with geometric mean MICs of 2.24 and 2.67mg/L for C. neoformans AFLP1/VNI, 1.38 and 1.53mg/L for C. neoformans AFLP1A/VNB/VNII and AFLP1B/VNII, and 1.85 and 0.68mg/L for Cryptococcus tetragattii, respectively. A significant difference between flucytosine geometric mean MICs of C. neoformans and C. tetragattii was observed (P=0.0002). The majority of isolates (n=66/68; 97.1%) had a wild-type MIC phenotype of all antifungal agents. This study demonstrates a favorable situation with respect to the tested antifungals agents. Continued surveillance of antifungal susceptibility profiles is important due to the high burden of cryptococcosis in Africa.

Hot topics in antifungal susceptibility testing: A new drug, a bad bug, sweeping caspofungin testing under the rug, and solving the ECV shrug

There are several new hot topics in antifungals and antifungal susceptibility testing. In this review, four topics of general interest to the clinical microbiology community are discussed. The first topic is the introduction of isavuconazole, a new triazole approved for clinical use in the US. The second is triazole resistance in Aspergillus fumigatus isolates. A specific set of mutations are being found with greater frequency in isolates globally, including the US. The third topic of interest is a word of caution about antifungal susceptibility testing for caspofungin in Candida isolates; some laboratories have reported susceptible isolates with high MIC values that would be interpreted as resistant. The final topic is an introduction to epidemiological cutoff values and their use in the clinical mycology laboratory.

The role of epidemiological cutoff values (ECVs/ECOFFs) in antifungal susceptibility testing and interpretation for uncommon yeasts and moulds

The role of antimicrobial susceptibility testing is to aid in selecting the best agent for the treatment of bacterial and fungal diseases. This has been best achieved by the setting of breakpoints by Clinical Laboratory Standards Institute (CLSI) for prevalent Candida spp. versus anidulafungin, caspofungin, micafungin, fluconazole, and voriconazole. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) also has set breakpoints for prevalent and common Candida and Aspergillus species versus amphotericin B, itraconazole, and posaconazole. Recently, another interpretive category, the epidemiological cut off value, could aid in the early identification of strains with acquired resistance mechanisms. CLSI has postulated that epidemiological cut off values may, with due caution, aid physicians in managing mycosis by species where breakpoints are not available. This review provides (1) the criteria and statistical approach to establishing and estimating epidemiological cut off values (ECVs), (2) the role of the epidemiological cut off value in establishing breakpoints, (3) the potential role of epidemiological cut off values in clinical practice, (4) and the wide range of CLSI-based epidemiological cut off values reported in the literature as well as EUCAST and Sensititre Yeast One-ECVs. Additionally, we provide MIC/MEC (minimal inhibitory concentrations/minimum effective concentrations) ranges/modes of each pooled distribution used for epidemiological cut off value calculation. We focus on the epidemiological cut off value, the new interpretive endpoint that will identify the non-wild type strains (defined as potentially harboring resistance mechanisms). However, we emphasize that epidemiological cut off values will not categorize a fungal isolate as susceptible or resistant as breakpoints do, because the former do not account for the pharmacology of the antifungal agent or the findings from clinical outcome studies.

Isavuconazole in the treatment of invasive aspergillosis and mucormycosis infections

We have a limited arsenal with which to treat invasive fungal infections caused by Aspergillus and Mucorales. The morbidity and mortality for both pathogens remains high. A triazole antifungal, isavuconazole, was recently granted approval by the US Food and Drug Administration and the European Medicines Agency for the treatment of invasive aspergillosis and mucormycosis. A randomized double-blind comparison trial for the treatment of invasive aspergillosis found isavuconazole noninferior to voriconazole. A separate, open-label study evaluating the efficacy of isavuconazole in the treatment of mucormycosis found comparable response rates to amphotericin B and posaconazole treated historical controls. The prodrug isavuconazonium sulfate is commercially available in both an oral and intravenous formulation and is generally well tolerated. Isavuconazole’s broad spectrum of activity, limited side effect profile, and favorable pharmacokinetics will likely solidify its place in therapy.

Pharmacokinetics and Concentration-Dependent Efficacy of Isavuconazole for Treatment of Experimental Invasive Pulmonary Aspergillosis

We studied the pharmacokinetics and efficacy of the broad-spectrum triazole isavuconazole for the treatment of experimental invasive pulmonary aspergillosis (IPA) in persistently neutropenic rabbits. Treatment started 24 h after endotracheal administration of Aspergillus fumigatus inoculum; study subjects included rabbits receiving orally administered prodrug isavuconazonium sulfate (BAL8557) equivalent to active moiety isavuconazole (ISA; BAL4815) at 20 (ISA20), 40 (ISA40), and 60 (ISA60) mg/kg (of body weight)/day, with an initial loading dose of 90 mg/kg (ISA90), and untreated rabbits (UC). There were significant concentration-dependent reductions of residual fungal burden (log CFU/gram) and of organism-mediated pulmonary injury, lung weights, and pulmonary infarct scores in ISA40- and ISA60-treated rabbits in comparison to those of UC (P < 0.001). ISA20-treated (P < 0.05), ISA40-treated, and ISA60-treated (P < 0.001) rabbits demonstrated significantly prolonged survival in comparison to that of UC. ISA40- and ISA60-treated animals demonstrated a significant decline of serum (1→3)-β-d-glucan levels (P < 0.05) and galactomannan indices (GMIs) during therapy following day 4 in comparison to progressive GMIs of UC (P < 0.01). There also were significantly lower concentration-dependent GMIs in bronchoalveolar lavage (BAL) fluid from ISA40- and ISA60-treated rabbits (P < 0.001). There was a direct correlation between isavuconazole plasma area under the concentration-time curve from 0 to 24 h (AUC0-24) and residual fungal burdens in lung tissues, pulmonary infarct scores, and total lung weights. In summary, rabbits treated with isavuconazole at 40 and 60 mg/kg/day demonstrated significant dose-dependent reduction of residual fungal burden, decreased pulmonary injury, prolonged survival, lower GMIs in serum and BAL fluid, and lower serum (1→3)-β-d-glucan levels.

Isavuconazole versus voriconazole for primary treatment of invasive mould disease caused by Aspergillus and other filamentous fungi (SECURE): a phase 3, randomised-controlled, non-inferiority trial

BACKGROUND

Isavuconazole is a novel triazole with broad-spectrum antifungal activity. The SECURE trial assessed efficacy and safety of isavuconazole versus voriconazole in patients with invasive mould disease.

METHODS

This was a phase 3, double-blind, global multicentre, comparative-group study. Patients with suspected invasive mould disease were randomised in a 1:1 ratio using an interactive voice-web response system, stratified by geographical region, allogeneic haemopoietic stem cell transplantation, and active malignant disease at baseline, to receive isavuconazonium sulfate 372 mg (prodrug; equivalent to 200 mg isavuconazole; intravenously three times a day on days 1 and 2, then either intravenously or orally once daily) or voriconazole (6 mg/kg intravenously twice daily on day 1, 4 mg/kg intravenously twice daily on day 2, then intravenously 4 mg/kg twice daily or orally 200 mg twice daily from day 3 onwards). We tested non-inferiority of the primary efficacy endpoint of all-cause mortality from first dose of study drug to day 42 in patients who received at least one dose of the study drug (intention-to-treat [ITT] population) using a 10% non-inferiority margin. Safety was assessed in patients who received the first dose of study drug. This study is registered with ClinicalTrials.gov, number NCT00412893.

FINDINGS

527 adult patients were randomly assigned (258 received study medication per group) between March 7, 2007, and March 28, 2013. All-cause mortality from first dose of study drug to day 42 for the ITT population was 19% with isavuconazole (48 patients) and 20% with voriconazole (52 patients), with an adjusted treatment difference of -1·0% (95% CI -7·8 to 5·7). Because the upper bound of the 95% CI (5·7%) did not exceed 10%, non-inferiority was shown. Most patients (247 [96%] receiving isavuconazole and 255 [98%] receiving voriconazole) had treatment-emergent adverse events (p=0·122); the most common were gastrointestinal disorders (174 [68%] vs 180 [69%]) and infections and infestations (152 [59%] vs 158 [61%]). Proportions of patients with treatment-emergent adverse events by system organ class were similar overall. However, isavuconazole-treated patients had a lower frequency of hepatobiliary disorders (23 [9%] vs 42 [16%]; p=0·016), eye disorders (39 [15%] vs 69 [27%]; p=0·002), and skin or subcutaneous tissue disorders (86 [33%] vs 110 [42%]; p=0·037). Drug-related adverse events were reported in 109 (42%) patients receiving isavuconazole and 155 (60%) receiving voriconazole (p<0·001).

INTERPRETATION

Isavuconazole was non-inferior to voriconazole for the primary treatment of suspected invasive mould disease. Isavuconazole was well tolerated compared with voriconazole, with fewer study-drug-related adverse events. Our results support the use of isavuconazole for the primary treatment of patients with invasive mould disease.

FUNDING

Astellas Pharma Global Development, Basilea Pharmaceutica International.