Antifungal susceptibilities among different serotypes of Cryptococcus gattii and Cryptococcus neoformans

Pulmonary Cryptococcosis

Pulmonary cryptococcosis describes an invasive lung mycosis caused by Cryptococcus neoformans or Cryptococcus gattii complex. It is often a high-consequence disease in both immunocompromised and immunocompetent populations, and may be misdiagnosed as pulmonary malignancy, leading to a delay in therapy. Epidemiology follows that of cryptococcal meningoencephalitis, with C. gattii infection more common in certain geographic regions. Diagnostic tools include histopathology, microscopy and culture, and the detection of cryptococcal polysaccharide antigen or Cryptococcus-derived nucleic acids. All patients with lung cryptococcosis should have a lumbar puncture and cerebral imaging to exclude central nervous system disease. Radiology is key, both as an adjunct to laboratory testing and as the initial means of detection in asymptomatic patients or those with non-specific symptoms. Pulmonary cryptococcomas (single or multiple) may also be associated with disseminated disease and/or cryptococcal meningitis, requiring prolonged treatment regimens. Optimal management for severe disease requires extended induction (amphotericin B and flucytosine) and consolidation therapy (fluconazole) with close clinical monitoring. Susceptibility testing is of value for epidemiology and in regions where relatively high minimum inhibitory concentrations to azoles (particularly fluconazole) have been noted. Novel diagnostic tools and therapeutic agents promise to improve the detection and treatment of cryptococcosis, particularly in low-income settings where the disease burden is high.

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.

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.

Multi-locus sequence typing reveals genotypic similarity in Nigerian Cryptococcus neoformans AFLP1/VNI of environmental and clinical origin

IntroductionPigeon droppings are among the major environmental sources of Cryptococcus neoformans AFLP1/VNI, from where the organism infects susceptible humans and animals resulting in cryptococcosis. Until now, C. neoformans AFLP1B/VNII was the only molecular type reported in Nigeria. Effective clinical treatment of this infection has occasionally been stymied by the emergence of antifungal non-susceptible, and resistant strains of C. neoformans AFLP1/VNI.Hypothesis/Gap StatementPigeon droppings harbour C. neoformans and HIV/AIDS patients are among the susceptible population to develop cryptococcal infection. Epidemiological data on cryptococcal prevalence is limited in Nigeria.AimTo investigate the environmental prevalence of C. neoformans in South-eastern Nigeria and compare the isolates with other lineages by using molecular and microbiological tools.MethodologyA total of 500 pigeon droppings and 300 blood samples of HIV/AIDS patients were collected, respectively, from five market squares and three tertiary healthcare centres within the Nsukka area of South-eastern Nigeria. The antifungal susceptibility of the C. neoformans isolates to amphotericin B, fluconazole, 5-fluorocytosine, itraconazole, voriconazole, posaconazole, and isavuconazole was investigated based on the CLSI M27-A3 protocol. Yeasts were identified by MALDI-TOF MS, thereafter Cryptococcus MLST was performed according to the International Society for Human and Animal Mycology (ISHAM) consensus scheme.Results C. neoformans was recovered from 6 (1.2 %) pigeon droppings and 6 (2 %) blood cultures of HIV/AIDS patients. Molecular analyses indicated that all cryptococcal isolates belong to serotype A and the AFLP1/VNI molecular type with sequence type (ST)32. Infection with C. neoformans was independent of sex and age of the patients investigated. All C. neoformans isolates were susceptible to the seven antifungal agents.ConclusionThis is the first report on the prevalence of C. neoformans AFLP1/VNI (ST32) in environmental and clinical samples from Nigeria. The antifungal susceptibility indicates that antifungal resistance by C. neoformans is yet a rare occurrence in Nigeria.

Cryptococcosis in patients with liver cirrhosis: Death risk factors and predictive value of prognostic models

BACKGROUND

Liver cirrhosis is associated with immune deficiency, which causes these patients to be susceptible to various infections, including cryptococcus infection. Mortality in cirrhotic patients with cryptococcosis has increased. The present study was to explore the risk factors of mortality and the predictive ability of different prognostic models.

METHODS

Forty-seven cirrhotic patients with cryptococcosis at a tertiary care hospital were included in this retrospective study. Data on demographics, clinical parameters, laboratory exams, diagnostic methods, medication during hospitalization, severity scores and prognosis were collected and analyzed. Student's t test and Mann-Whitney test were used to compare characteristics of survivors and non-survivors at a 90-day follow-up and cerebrospinal fluid (CSF) manifestations of cryptococcal meningitis. Multivariate Cox regression analysis was used to identify the independent risk factors for mortality. Kaplan-Meier curves were used to analyze patient survival. Receiver operating characteristic (ROC) curves were used to evaluate the different prognostic factors.

RESULTS

The 30- and 90-day survival rates were 93.6% and 80.9%, respectively, in cirrhotic patients with cryptococcosis. Cryptogenic liver diseases [hazard ratio (HR) = 7.567, 95% confidence interval (CI): 1.616-35.428, P = 0.010], activated partial thromboplastin time (APTT) (HR = 1.117, 95% CI: 1.016-1.229, P = 0.022) and Child-Pugh score (HR = 2.146, 95% CI: 1.314-3.504, P = 0.002) were risk factors for 90-day mortality in cirrhotic patients with cryptococcosis. Platelet count (HR = 0.965, 95% CI: 0.940-0.991, P = 0.008) was a protective factor. APTT (HR = 1.120, 95% CI: 1.044-1.202, P = 0.002) and Child-Pugh score (HR = 1.637, 95% CI: 1.086-2.469, P = 0.019) were risk factors for 90-day mortality in cirrhotic patients with cryptococcal meningitis. There was significant difference in the percentage of lymphocytes in CSF between survivors and non-survivors [60.0 (35.0-75.0) vs. 95.0 (83.8-97.2), P < 0.001]. The model of end-stage liver disease-sodium (MELD-Na) score was more accurate for predicting 30-day mortality both in patients with cryptococcosis [area under curve (AUC): 0.826, 95% CI: 0.618-1.000] and those with cryptococcal meningitis (AUC: 0.742, 95% CI: 0.560-0.924); Child-Pugh score was more useful for predicting 90-day mortality in patients with cryptococcosis (AUC: 0.823, 95% CI: 0.646-1.000) and those with cryptococcal meningitis (AUC: 0.815, 95% CI: 0.670-0.960).

CONCLUSIONS

These results showed that cryptogenic liver diseases, APTT and Child-Pugh score were associated with mortality in cirrhotic patients with cryptococcosis and cryptococcal meningitis. MELD-Na score was important for predicting 30-day mortality, and Child-Pugh score was critical for predicting 90-day mortality.

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.

In Silico Structural Modeling and Analysis of Interactions of Tremellomycetes Cytochrome P450 Monooxygenases CYP51s with Substrates and Azoles

Cytochrome P450 monooxygenase CYP51 (sterol 14α-demethylase) is a well-known target of the azole drug fluconazole for treating cryptococcosis, a life-threatening fungal infection in immune-compromised patients in poor countries. Studies indicate that mutations in CYP51 confer fluconazole resistance on cryptococcal species. Despite the importance of CYP51 in these species, few studies on the structural analysis of CYP51 and its interactions with different azole drugs have been reported. We therefore performed in silico structural analysis of 11 CYP51s from cryptococcal species and other Tremellomycetes. Interactions of 11 CYP51s with nine ligands (three substrates and six azoles) performed by Rosetta docking using 10,000 combinations for each of the CYP51-ligand complex (11 CYP51s × 9 ligands = 99 complexes) and hierarchical agglomerative clustering were used for selecting the complexes. A web application for visualization of CYP51s' interactions with ligands was developed (http://bioshell.pl/azoledocking/). The study results indicated that Tremellomycetes CYP51s have a high preference for itraconazole, corroborating the in vitro effectiveness of itraconazole compared to fluconazole. Amino acids interacting with different ligands were found to be conserved across CYP51s, indicating that the procedure employed in this study is accurate and can be automated for studying P450-ligand interactions to cater for the growing number of P450s.

Nitrogen concentration affects amphotericin B and fluconazole tolerance of pathogenic cryptococci

Environmental stress often causes phenotypic changes among pathogenic cryptococci, such as altered antifungal susceptibility, changes in capsule and melanin formation, as well as altered levels of the membrane sterol and antifungal target, ergosterol. We therefore hypothesised that nitrogen limitation, a prevalent environmental stress in the natural habitat of these yeasts, might affect virulence and antifungal susceptibility. We tested the effect of different nitrogen concentrations on capsule, melanin and ergosterol biosynthesis, as well as amphotericin B (AmB) and fluconazole (FLU) susceptibility. This was achieved by culturing cryptococcal strains representing Cryptococcus neoformans and Cryptococcus gattii in media with high (0.53 g/l), control (0.42 g/l) and low (0.21 g/l) NH4Cl concentrations. India ink staining was used to determine capsule thickness microscopically, while melanin and ergosterol content were determined spectrophotometrically. We found that lower nitrogen concentrations enhanced both ergosterol and capsule biosynthesis, while a variable effect was observed on melanisation. Evaluation of drug tolerance using time-kill methodology, as well as tests for FLU heteroresistance, revealed that the low nitrogen cultures had the highest survival percentages in the presence of both AmB and FLU, and showed the highest frequency of FLU heteroresistance, suggesting that nitrogen concentration may indeed influence drug tolerance.

Cryptococcosis

Cryptococcosis is an invasive fungal infection of global significance caused by yeasts of the genus Cryptococcus. The prevalence of HIV in certain areas of the world and the expanding population of immunocompromised patients contribute to the ongoing global disease burden. Point-of-care serologic testing has allowed for more rapid diagnosis and implementation of screening programs in resource-limited settings. Management involves therapy aimed at reduction in fungal burden, maintenance of intracranial pressure, and optimization of host immunity. Despite diagnostic and therapeutic advances, cryptococcosis continues to be a disease with unacceptably high incidence and mortality, particularly in resource-limited settings.

Antifungal Resistance among Less Prevalent Candida Non-albicans and Other Yeasts versus Established and under Development Agents: A Literature Review

Fungal diseases and antifungal resistance continue to increase, including those caused by rare or emerging species. However, the majority of the published in vitro susceptibility data are for the most common fungal species. We reviewed the literature in order to pool reference minimal inhibitory concentration (MIC) data (Clinical and Laboratory Standards Institute—CLSI and European Committee on Antimicrobial Susceptibility—EUCAST) for rare/non-prevalent Candida and other yeast species. MIC results were compared with those for Candida albicans, C. glabrata, and C. krusei. Data were listed for twenty rare and emerging Candida spp., including C. auris, as well as two Cryptococcus spp., two Trichosporon spp., Saccharomyces cerevisiae and five Malassezia spp. The best detectors of antimicrobial resistance are the breakpoints, which are not available for the less common Candida species. However, epidemiological cutoff values (ECVs/ECOFFs) have been calculated using merely in vitro data for both reference methods for various non-prevalent yeasts and recently the CLSI has established ECVs for other Candida species. The ECV could identify the non-wild type (NWT or mutants) isolates with known resistance mechanisms. Utilizing these ECVs, we were able to report additional percentages of NWT, especially for non-prevalent species, by analyzing the MIC distributions in the literature. In addition, since several antifungal drugs are under development, we are listing MIC data for some of these agents.

Molecular types of Cryptococcus neoformans and Cryptococcus gattii in Western Australia and correlation with antifungal susceptibility

Cryptococcus neoformans and Cryptococcus gattii species complexes have a worldwide distribution; however, there is geographical variation in the prevalence of different molecular types. Additionally, antifungal susceptibility differences between molecular types have been demonstrated. This study investigates the distribution of cryptococcal molecular types among human clinical isolates over a 10-year period from a Western Australian population. Molecular type was determined based on polymorphisms in the phospholipase gene locus identified through amplification and sequencing. Minimum inhibitory concentrations (MICs) were identified for fluconazole, 5-fluorocytosine, posaconazole, itraconazole, voriconazole, and amphotericin B. Most isolates were C. neoformans complex (42) of which over half were molecular type VNI (22) followed by VNII (20). Among the remaining C. gattii complex (13) the majority were VGI (11) with VGII (2) uncommonly found. All isolates demonstrated low MICs to antifungal agents including fluconazole. Geometric mean MIC values against 5-fluorocytosine for VNI (1.741 mg/l) were significantly higher than those for VGI (0.47 mg/l, P = .002). Similarly fluconazole geometric mean MICs against fluconazole for VNI (2.3 mg/l) were significantly higher than VNII (0.87 mg/l, P = .036). These data reveal the presence of four molecular types (VNI, VNII, VGI and VGII) within clinical Western Australian cryptococcal isolates and, while elevated antifungal MICs were not encountered, significant molecular type dependent differences in susceptibility were found.

Cryptococcosis in solid organ transplantation-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of cryptococcosis in the pre- and post-transplant period. The current update now includes a discussion of cryptococcosis, which is the third most common invasive fungal infection in SOT recipients. Infection often occurs a year after transplantation; however, early infections occur and donor-derived infections have been described within 3 months after transplant. There are two main species that cause infection, Cryptococcus neoformans and C gattii. Clinical onset may be insidious, but headaches, fevers, and mental status changes should warrant diagnostic testing. The lateral flow cryptococcal antigen assay is now the preferred test from serum and cerebrospinal fluid due to its rapidity, accuracy, and cost. A lumbar puncture with measurement of opening pressure is recommended for patients with suspected or proven cryptococcosis. Lipid amphotericin B plus 5-flucytosine is used as initial treatment of meningitis, disseminated infection, and moderate-to-severe pulmonary infection, followed by fluconazole as consolidation therapy. Fluconazole is effective for mild-to-moderate pulmonary infection. Immunosuppression reduction as part of management may lead to immune reconstitution syndrome that may resemble active disease.

Undiagnosed Cryptococcus gattii meningitis leading to subsequent ventriculoperitoneal shunt infection in a patient with symptoms of normal pressure hydrocephalus: case report and literature review

Background

Cryptococcus gattii is known to be an etiologic agent of human cryptococcosis, particularly in immunocompetent persons. C. gattii infection usually involves the central nervous system, the respiratory tract, or may be disseminated. Here we report an atypical manifestation of C. gattii infection in a patient who had C. gattii meningitis complicating the ventriculoperitoneal (VP) shunt infection and concurrent infected intraabdominal VP shunt pseudocyst.

Case presentation

A 66-year-old Thai female was initially diagnosed with normal pressure hydrocephalus (NPH) and underwent programmable VP shunt placement. However, she still suffered from recurrent communicating hydrocephalus with in-place VP shunt, and later developed recurrent gait impairment, chronic abdominal pain and abdominal mass. Radiological studies demonstrated recurrent hydrocephalus and a very large intraabdominal VP shunt pseudocyst. C. gattii was isolated from both the cerebrospinal fluid and the pseudocyst aspiration. C. gattii meningitis complicating the VP shunt infection and concurrent infected intraabdominal VP shunt pseudocyst was diagnosed. Prolonged antifungal therapy, removal of the infected VP shunt with subsequent implant of a new shunt provided a good outcome.

Conclusion

Chronic C. gattii meningitis should be aware in a patient presenting with normal pressure hydrocephalus. Under-diagnosed cryptococcal meningitis following VP shunt insertion for treating the hydrocephalus can render a complicated VP shunt infection including infected VP shunt pseudocyst.

Spotlight on isavuconazole in the treatment of invasive aspergillosis and mucormycosis: design, development, and place in therapy

In recent decades, important advances have been made in the diagnosis and treatment of invasive aspergillosis (IA) and mucormycosis. One of these advances has been the introduction of isavuconazole, a second-generation broad spectrum triazole with a favorable pharmacokinetic and safety profile and few drug–drug interactions. Phase III trials in patients with IA and mucormycosis demonstrated that isavuconazole has similar efficacy to voriconazole for the treatment of IA (SECURE trial) and liposomal amphotericin B for the treatment of mucormycosis (VITAL trial with subsequent case–control analysis) and a favorable safety profile with significantly fewer ocular, hepatobiliary, and skin and soft tissue adverse events compared to voriconazole. As a result, recent IA guidelines recommend isavuconazole (together with voriconazole) as gold standard treatment for IA in patients with underlying hematological malignancies. In contrast to liposomal amphotericin B, isavuconazole can be safely administered in patients with reduced renal function and is frequently used for the treatment of mucormycosis in patients with reduced renal function. Updated guidelines on mucormycosis are needed to reflect the current evidence and give guidance on the use of isavuconazole for mucormycosis. Studies are needed to evaluate the role of isavuconazole for 1) anti-mold prophylaxis in high-risk patients, 2) salvage treatment for IA and mucormycosis, and 3) treatment for other mold infections such as Scedosporium apiospermum.

Clinical characteristics of disseminated cryptococcosis in previously healthy children in China

Background

Disseminated cryptococcosis is a rare and fatal disease, and limited data exist regarding it in children. This study aimed to investigate the clinical characteristics of disseminated cryptococcosis in previously healthy children in China.

Methods

Hospitalized patients with disseminated cryptococcosis were enrolled during January 1996 to December 2015 in Beijing Children’s Hospital, Capital Medical University, China. Data on clinical manifestations, laboratory tests, treatment, and prognosis were evaluated.

Results

A total of 52 pediatric patients with no underlying disease were enrolled, including 38 boys and 14 girls. Only 10 cases had a history of exposure to pigeon droppings. Fever, cough, and hepatomegaly were 3 main manifestations of disseminated cryptococcosis. However, headache was more common in patients with central nervous system (CNS) invasion than in patients with non-CNS invasion (P < 0.05). Lung (96.2%, 50/52) was the most commonly invaded organ, but only 9.6% (5/52) of patients had respiratory signs. The most common findings on chest imaging were hilar or mediastinal lymphadenopathy (46.8%, 22/47), and nodules (44.7%, 21/47), including small nodules in a scattered distribution (57.1%, 12/21) or miliary distribution (42.9%, 9/25), especially localized in subpleural area. Subsequent invasion occurred in the CNS, abdomen lymph nodes, liver, spleen, peripheral lymph nodes, and skin. In all patients, 42.3% (22/52) and 51.9% (27/52) had elevated eosinophils or IgE, respectively. The positive rate of serum cryptococcal antigen was higher, especially in patients with CNS invasion (approximately 83.3%), than with other primary methods used for pathogen detection, including cerebrospinal fluid (CSF) cryptococcal antigen, cultures of blood, bone marrow, or CSF, and CSF ink staining. The overall mortality rate of pediatric patients in our study was 11.5% (6/52). Some cases had long-term sequela, including hydrocephalus, cirrhosis, or blindness.

Conclusions

Disseminated cryptococcosis can occur in previously healthy or immunocompetent children in China. Lung and CNS were most commonly invaded by this disease. Furthermore, most cases usually showed no obvious or specific symptoms or signs, and therefore pediatricians should pay more careful attention to identify this disease.

Activity of Scorpion Venom-Derived Antifungal Peptides against Planktonic Cells of Candida spp. and Cryptococcus neoformans and Candida albicans Biofilms

The incidence of fungal infections has been increasing in the last decades, while the number of available antifungal classes remains the same. The natural and acquired resistance of some fungal species to available therapies, associated with the high toxicity of these drugs on the present scenario and makes an imperative of the search for new, more efficient and less toxic therapeutic choices. Antimicrobial peptides (AMPs) are a potential class of antimicrobial drugs consisting of evolutionarily conserved multifunctional molecules with both microbicidal and immunomodulatory properties being part of the innate immune response of diverse organisms. In this study, we evaluated 11 scorpion-venom derived non-disulfide-bridged peptides against Cryptococcus neoformans and Candida spp., which are important human pathogens. Seven of them, including two novel molecules, showed activity against both genera with minimum inhibitory concentration values ranging from 3.12 to 200 μM and an analogous activity against Candida albicans biofilms. Most of the peptides presented low hemolytic and cytotoxic activity against mammalian cells. Modifications in the primary peptide sequence, as revealed by in silico and circular dichroism analyses of the most promising peptides, underscored the importance of cationicity for their antimicrobial activity as well as the amphipathicity of these molecules and their tendency to form alpha helices. This is the first report of scorpion-derived AMPs against C. neoformans and our results underline the potential of scorpion venom as a source of antimicrobials. Further characterization of their mechanism of action, followed by molecular optimization to decrease their cytotoxicity and increase antimicrobial activity, is needed to fully clarify their real potential as antifungals.

Identification and Characterization of VNI/VNII and Novel VNII/VNIV Hybrids and Impact of Hybridization on Virulence and Antifungal Susceptibility Within the C. neoformans/C. gattii Species Complex

Cryptococcus neoformans and C. gattii are pathogenic basidiomycetous yeasts and the commonest cause of fungal infection of the central nervous system. Cryptococci are typically haploid but several inter-species, inter-varietal and intra-varietal hybrids have been reported. It has a bipolar mating system with sexual reproduction occurring normally between two individuals with opposite mating types, α and a. This study set out to characterize hybrid isolates within the C. neoformans/C. gattii species complex: seven unisexual mating intra-varietal VNI/VNII (αAAα) and six novel inter-varietal VNII/VNIV (aADα). The URA5-RFLP pattern for VNII/VNIV (aADα) differs from the VNIII (αADa) hybrids. Analysis of the allelic patterns of selected genes for AD hybrids showed 79% or more heterozygosis for the studied loci except for CBS132 (VNIII), which showed 50% of heterozygosity. MALDI-TOF MS was applied to hybrids belonging to different sero/mating type allelic patterns. All hybrid isolates were identified as belonging to the same hybrid group with identification scores ranging between 2.101 to 2.634. All hybrids were virulent when tested in the Galleria mellonella (wax moth) model, except for VNII/VNIV (aADα) hybrids. VNI/VGII hybrids were the most virulent hybrids. Hybrids recovered from larvae manifested a significant increase in capsule and total cell size and produced a low proportion (5-10%) of giant cells compared with the haploid control strains. All strains expressed the major virulence factors-capsule, melanin and phospholipase B-and grew well at 37°C. The minimal inhibitory concentration of nine drugs was measured by micro-broth dilution and compared with published data on haploid strains. MICs were similar amongst hybrids and haploid parental strains. This is the first study reporting natural same sex αAAα intra-varietal VNI/VNII hybrids and aADα inter-varietal VNII/VNIV hybrids.

Identification of QTLs Associated with Virulence Related Traits and Drug Resistance in Cryptococcus neoformans

Cryptococcus neoformans is a basidiomycete fungus capable of causing deadly meningoenchephilitis, primarily in immunocompromised individuals. Formerly, C. neoformans was composed of two divergent lineages, but these have recently been elevated to species status, now C. neoformans (formerly C. neoformans var. grubii) and C. deneoformans (formerly C. neoformans var. neoformans). While both species can cause deadly infections in humans, C. neoformans is much more prevalent in clinical settings than C. deneoformans. However, the genetic factors contributing to their significant differences in virulence remain largely unknown. Quantitative trait locus (QTL) mapping is a powerful tool that can be used to identify genomic regions associated with phenotypic differences between strains. Here, we analyzed a hybrid cross between these two species and identified a total of 23 QTL, including five for melanin production, six for cell size, one for cell wall thickness, five for the frequency of capsule production, three for minimal inhibitory concentration (MIC) of fluconazole in broth, and three for MIC on solid medium. For the fluconazole resistance-associated QTL, three showed environment and/or concentration-specific effects. Our results provide a large number of candidate gene regions from which to explore the molecular bases for phenotypic differences between C. neoformans and C. deneoformans.

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.

Population Pharmacokinetics of Isavuconazole from Phase 1 and Phase 3 (SECURE) Trials in Adults and Target Attainment in Patients with Invasive Infections Due to Aspergillus and Other Filamentous Fungi

Isavuconazole, the active moiety of the water-soluble prodrug isavuconazonium sulfate, is a triazole antifungal agent used for the treatment of invasive fungal infections. The objective of this analysis was to develop a population pharmacokinetic (PPK) model to identify covariates that affect isavuconazole pharmacokinetics and to determine the probability of target attainment (PTA) for invasive aspergillosis patients. Data from nine phase 1 studies and one phase 3 clinical trial (SECURE) were pooled to develop the PPK model (NONMEM, version 7.2). Stepwise covariate modeling was performed in Perl-speaks-NONMEM, version 3.7.6. The area under the curve (AUC) at steady state was calculated for 5,000 patients by using Monte Carlo simulations. The PTA using the estimated pharmacodynamic (PD) target value (total AUC/MIC ratio) estimated from in vivo PD studies of invasive aspergillosis over a range of MIC values was calculated using simulated patient AUC values. A two-compartment model with a Weibull absorption function and a first-order elimination process adequately described plasma isavuconazole concentrations. The mean estimate for isavuconazole clearance was 2.360 liters/h (percent coefficient of variation [%CV], 34%), and the mean AUC from 0 to 24 h (AUC0-24) was ∼100 mg·h/liter. Clearance was approximately 36% lower in Asians than in Caucasians. The PTA calculated over a range of MIC values by use of the nonneutropenic murine efficacy index corresponding to 90% survival indicated that adequate isavuconazole exposures were achieved in >90% of simulated patients to treat infections with MICs up to and including 1 mg/liter according to European Committee on Antimicrobial Susceptibility Testing methodology and in >90% of simulated patients for infections with MICs up to and including 0.5 mg/liter according to Clinical and Laboratory Standards Institute methodology. The highest MIC result for PTA was the same for Caucasian and Asian patients.

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.

Isavuconazole Treatment of Cryptococcosis and Dimorphic Mycoses

BACKGROUND

Invasive fungal diseases (IFD) caused by Cryptococcus and dimorphic fungi are associated with significant morbidity and mortality. Isavuconazole (ISAV) is a novel, broad-spectrum, triazole antifungal agent (IV and by mouth [PO]) developed for the treatment of IFD. It displays potent activity in vitro against these pathogens and in this report we examine outcomes of patients with cryptococcosis or dimorphic fungal infections treated with ISAV.

METHODS

The VITAL study was an open-label nonrandomized phase 3 trial conducted to evaluate the efficacy and safety of ISAV treatment in management of rare IFD. Patients received ISAV 200 mg 3 times daily for 2 days followed by 200 mg once-daily (IV or PO). Proven IFD and overall response at end of treatment (EOT) were determined by an independent, data-review committee. Mortality and safety were also assessed.

RESULTS

Thirty-eight patients received ISAV for IFD caused by Cryptococcus spp. (n = 9), Paracoccidioides spp. (n = 10), Coccidioides spp. (n = 9), Histoplasma spp. (n = 7) and Blastomyces spp. (n = 3). The median length of therapy was 180 days (range 2-331 days). At EOT 24/38 (63%) patients exhibited a successful overall response. Furthermore, 8 of 38 (21%) had stable IFD at the end of therapy without progression of disease, and 6 (16%) patients had progressive IFD despite this antifungal therapy. Thirty-three (87%) patients experienced adverse events.

CONCLUSIONS

ISAV was well tolerated and demonstrated clinical activity against these endemic fungi with a safety profile similar to that observed in larger studies, validating its broad-spectrum in vitro activity and suggesting it may be a valuable alternative to currently available agents.

CLINICAL TRIALS REGISTRATION

NCT00634049.

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.

Cryptococcus neoformans isolates from Yaoundé human immunodeficiency virus-infected patients exhibited intra-individual genetic diversity and variation in antifungal susceptibility profiles between isolates from the same patient

Cryptococcal meningitis is a dreadful opportunistic fungal infection amongst human immunodeficiency virus (HIV)-infected patients. One complication in the management of the disease is the possible infection of a patient by two or more different strains of Cryptococcus neoformans. This study investigated the intra-individual genetic diversity and antifungal susceptibility of C. neoformans isolates from Yaoundé (Cameroon) HIV-infected patients with cryptococcal meningitis. Twenty-five clinical isolates were obtained during a prospective study. Five colonies were randomly collected from each initial sample. The 150 isolates obtained (125 colonies and 25 initial samples) were submitted to serotyping by multiplex PCR. Genotyping analyses were achieved using RFLP, and minisatellite- and microsatellite-length polymorphism. The antifungal susceptibility testing was carried out using a Sensititre YeastOne kit. Seven antifungals were tested: itraconazole, fluconazole, amphotericin B, ketoconazole, 5-fluorocytosine, posaconazole and voriconazole. The 150 isolates were identified as C. neoformans serotype A and genotype VNI. The microsatellite and minisatellite sequence analyses generated 15 genotypes. Six out of 25 (24 %) patients were found to be infected by two different genotypes. Antifungal susceptibility showed several profiles: posaconazole (0.015-0.25 µg ml-1), amphotericin B (0.06-1 µg ml-1), fluconazole (0.5-16 µg ml-1), itraconazole (0.008-0.12 µg ml-1), ketoconazole (0.008-0.12 µg ml-1), 5-fluorocytosine (0.25-16 µg ml-1) and voriconazole (0.008-0.12 µg ml-1). It was noted that isolates from the same patient might present different susceptibility profiles to an antifungal drug with differences of more than four dilutions. The results achieved highlighted the possible presence of isolates with different genotypes in a patient with dissimilar antifungal susceptibility profiles during a single episode of cryptococcal meningitis.

The Investigational Fungal Cyp51 Inhibitor VT-1129 Demonstrates Potent In Vitro Activity against Cryptococcus neoformans and Cryptococcus gattii

Thein vitroactivities of the novel fungal Cyp51 inhibitor VT-1129 were evaluated against a large panel ofCryptococcus neoformansandCryptococcus gattiiisolates. VT-1129 demonstrated potent activities against bothCryptococcusspecies as demonstrated by low MIC50and MIC90values. ForC. gattii, thein vitropotency was maintained against all genotypes. In addition, significantly lower geometric mean MICs were observed for VT-1129 than for fluconazole againstC. neoformans, including isolates with reduced fluconazole susceptibility.

Pharmacokinetics and safety of posaconazole delayed-release tablets for invasive fungal infections

Posaconazole is a broad-spectrum triazole antifungal agent with potent activity against various pathogenic fungi, including yeast and moulds. Clinical studies have demonstrated that this agent is efficacious as prophylaxis against invasive fungal infections in patients at high risk, and may also be useful as salvage therapy against invasive aspergillosis and mucormycosis. However, the bioavailability of posaconazole following administration by oral suspension, which was the only formulation clinically available for many years, is highly variable and negatively influenced by several factors. Because of this, many patients had subtherapeutic or undetectable posaconazole levels when the oral suspension was used. To overcome this limitation, a delayed-release tablet was developed and is now available for clinical use. Hot-melt extrusion technology is used to combine a pH-sensitive polymer with posaconazole to produce a formulation that releases the drug in the elevated pH of the intestine where absorption occurs rather than in the low-pH environment of the stomach. This results in enhanced bioavailability and increased posaconazole exposure. Studies in healthy volunteers have demonstrated significantly higher and more consistent exposures with the tablet formulation compared to the oral suspension. In addition, pharmacokinetic parameters following administration of the tablets were not significantly affected by medications that raise gastric pH or increase gastric motility, and the tablets could also be administered without regard to food. Similar results have also been found in patients at high risk for invasive fungal infections who have received posaconazole tablets. The tablet formulation also appears to be well tolerated to date, although data regarding clinical efficacy are needed.

Antifungal susceptibility of clinical and environmental Cryptococcus neoformans and Cryptococcus gattii isolates in Jabalpur, a city of Madhya Pradesh in Central India

In this study, we present antifungal susceptibility data of clinical and environmental isolates of Central Indian Cryptococcus neoformans (Serotype A, n = 8 and n = 50 respectively) and Cryptococcus gattii (Serotype B, n = 01 and n = 04 respectively). Susceptibilities to fluconazole, itraconazole and ketoconazole were determined by using NCCLS broth micro-dilution methodology. The total number of resistant strains for fluconazole in case of C. neoformans and C. gattii showed a significant difference by using chi-square test (p < 0.05*), while considering fisher's exact p value was nonsignificant (p > 0.05). However, the total number of resistant strains for itraconazole and ketoconazole was not found statistically significant. A comparison of geometric means of clinical and environmental strains of C. gattii and C. neoformans was not found statistically significant using student ‘t’ test (p value > 0.05 NS). Though less, the antifungal data obtained in this study suggests that primary resistance among environmental and clinical isolates of C. neoformans and C. gattii against tested antifungal was present and C. gattii comparatively was less susceptible than C. neoformans var. grubii isolates to fluconazole than to itraconazole and ketoconazole. A continuous surveillance of antifungal susceptibility of clinical and environmental isolates of C. neoformans and C. gattii is desirable to monitor the emergence of any resistant strains for better management of cryptococcosis patients.

[Cryptococcosis during HIV infection]

Cryptococcosis is a cosmopolitan fungal serious condition due to an encapsulated yeast Cryptococcus neoformans. This is the systemic fungal infection the most common in HIV infection. This yeast is present in the environment and its main entrance in the body is the respiratory tract. Its gravity is linked to its tropism for the central nervous system. It generally affects subjects with severe deficit of cellular immunity and in particular, patients living with HIV. The diagnosis of neuromeningeal cryptococcosis is based on the detection of encapsulated yeasts at microscopic examination of cerebrospinal fluid, the detection of capsular polysaccharide antigen in serum or cerebrospinal fluid, but especially on the culture. A staging is always essential. The prognosis is severe. The control of intracranial hypertension is a major element of prognosis.

Role of New Antifungal Agents in the Treatment of Invasive Fungal Infections in Transplant Recipients: Isavuconazole and New Posaconazole Formulations

Invasive fungal infections are a major cause of morbidity and mortality among solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients. Transplant patients are at risk for such invasive fungal infections. The most common invasive fungal infections are invasive candidiasis in the SOT and invasive aspergillosis in the HSCT. In this article, we will discuss the epidemiology of invasive fungal infections in the transplant recipients and susceptibility patterns of the fungi associated with these infections. Additionally, the pharmacology and clinical efficacy of the new antifungal, isavuconazole, and the new posaconazole formulations will be reviewed. Isavuconazole is a new extended-spectrum triazole that was recently approved for the treatment of invasive aspergillosis and mucormycosis. Advantages of this triazole include the availability of a water-soluble intravenous formulation, excellent bioavailability of the oral formulation, and predictable pharmacokinetics in adults. Posaconazole, a broad-spectrum triazole antifungal agent, is approved for the prevention of invasive aspergillosis and candidiasis in addition to the treatment of oropharyngeal candidiasis. Posaconazole oral suspension solution has shown some limitations in the setting of fasting state absorption, elevated gastrointestinal pH, and increased motility. The newly approved delayed-release oral tablet and intravenous solution formulations provide additional treatment options by reducing interpatient variability and providing flexibility in these set of critically ill patients. This review will detail these most recent studies.

Isavuconazole, a broad-spectrum triazole for the treatment of systemic fungal diseases

The prodrug isavuconazonium sulfate (BAL8557) is an extended-spectrum water-soluble triazole, developed for the treatment of severe invasive and life-threatening fungal diseases. Its active moiety, BAL4815, is a potent inhibitor of ergosterol biosynthesis, resulting in the disruption of fungal membrane structure and function. The active compound shows broad-spectrum of activity and potency against all major opportunistic fungi, such as Aspergillus spp., Candida spp., Cryptococcus spp., Mucorales, Black yeasts and their filamentous relatives and the true pathogenic fungi, including Histoplasma capsulatum and Blastomyces dermatitidis. It is currently in Phase III clinical development for treatment of aspergillosis, candidiasis and mucormycosis, as well as other rare fungi infections. We reviewed the pharmacokinetic and pharmacodynamic characteristics of isavuconazole, and its microbiological and clinical investigation progress in advanced stages of development.

Isavuconazole: A New Broad-Spectrum Triazole Antifungal Agent

Isavuconazole is a new extended-spectrum triazole with activity against yeasts, molds, and dimorphic fungi. It is approved for the treatment of invasive aspergillosis and mucormycosis. Advantages of this triazole include the availability of a water-soluble intravenous formulation, excellent bioavailability of the oral formulation, and predictable pharmacokinetics in adults. A randomized, double-blind comparison clinical trial for treatment of invasive aspergillosis found that the efficacy of isavuconazole was noninferior to that of voriconazole. An open-label trial that studied primary as well as salvage therapy of invasive mucormycosis showed efficacy with isavuconazole that was similar to that reported for amphotericin B and posaconazole. In patients in these studies, as well as in normal volunteers, isavuconazole was well tolerated, appeared to have few serious adverse effects, and had fewer drug-drug interactions than those noted with voriconazole. As clinical experience increases, the role of this new triazole in the treatment of invasive fungal infections will be better defined.

The 'cephalosporin era' of triazole therapy: isavuconazole, a welcomed newcomer for the treatment of invasive fungal infections

INTRODUCTION

Invasive fungal infections remain frequent life-threatening complications in immunocompromised patients. Each of the currently available antifungals has limitations in terms of pharmacokinetic and pharmacodynamic profile, spectrum of efficacy, and tolerability. Isavuconazole (ISA) is a new generation, broad-spectrum triazole that has a favorable spectrum of efficacy and is available in both intravenous and oral forms. Recent Phase III clinical studies showed that ISA had comparable efficacy to voriconazole for the treatment of a variety of mould infections.

AREAS COVERED

This review summarizes the literature on the use of ISA. PubMed was searched for publications in English from 2006 to December 2014 using the terms 'ISA', 'BAL4815', and 'BAL 8557'. Relevant publications were reviewed and reference lists were examined for further publications. Conference abstracts from the meeting during 2013 - 2014 were also reviewed.

EXPERT OPINION

ISA is a new broad spectrum triazole antifungal for the treatment of invasive fungal disease available as oral and intravenous formulations, and the ability to be administered as a once-daily regimen. ISA has broad-spectrum in vitro activity, favorable pharmacokinetic profile, and good tolerability. ISA may be considered for primary treatment for a vast variety of invasive fungal infections. Further study of ISA given as prophylaxis, combination, or salvage therapy is warranted.

Cryptococcus gattii infections

Understanding of the taxonomy and phylogeny of Cryptococcus gattii has been advanced by modern molecular techniques. C. gattii probably diverged from Cryptococcus neoformans between 16 million and 160 million years ago, depending on the dating methods applied, and maintains diversity by recombining in nature. South America is the likely source of the virulent C. gattii VGII molecular types that have emerged in North America. C. gattii shares major virulence determinants with C. neoformans, although genomic and transcriptomic studies revealed that despite similar genomes, the VGIIa and VGIIb subtypes employ very different transcriptional circuits and manifest differences in virulence phenotypes. Preliminary evidence suggests that C. gattii VGII causes severe lung disease and death without dissemination, whereas C. neoformans disseminates readily to the central nervous system (CNS) and causes death from meningoencephalitis. Overall, currently available data indicate that the C. gattii VGI, VGII, and VGIII molecular types more commonly affect nonimmunocompromised hosts, in contrast to VGIV. New, rapid, cheap diagnostic tests and imaging modalities are assisting early diagnosis and enabling better outcomes of cerebral cryptococcosis. Complications of CNS infection include increased intracranial pressure, severe neurological sequelae, and development of immune reconstitution syndrome, although the mortality rate is low. C. gattii VGII isolates may exhibit higher fluconazole MICs than other genotypes. Optimal therapeutic regimens are yet to be determined; in most cases, initial therapy with amphotericin B and 5-flucytosine is recommended.

Isavuconazole

Objective: To review the pharmacology, chemistry, in vitro susceptibility, pharmacokinetics, clinical efficacy, safety, tolerability, dosage, and administration of isavuconazole, a triazole antifungal agent. Data Sources: Studies and reviews were identified through an English language MEDLINE search (1978 to March 2015) and from http://www.clinicaltrials.gov , Food and Drug Administration (FDA) briefing documents, program abstracts from international symposia, and the manufacturer’s Web site. Study Selection and Data Extraction: All published and unpublished trials, abstracts, in vitro and preclinical studies, and FDA briefing documents were reviewed. Data Synthesis: Isavuconazole has activity against a number of clinically important yeasts and molds, including Candida spp, Aspergillus spp, Cryptococcus neoformans, and Trichosporon spp and variable activity against the Mucorales. Isavuconazole, available for both oral and intravenous administration, is characterized by slow elimination allowing once-daily dosing, extensive tissue distribution, and high (>99%) protein binding. The most commonly reported adverse events, which are mild and limited in nature, include nausea, diarrhea, and elevated liver function tests. Its drug interaction potential appears to be similar to other azole antifungals but less than those observed with voriconazole. Comparative trials are under way or have been recently completed for the treatment of candidemia, invasive candidiasis and aspergillosis, and rare mold infections. Conclusions: Isavuconazole has a broad spectrum of activity and favorable pharmacokinetic properties, providing an advantage over other currently available broad-spectrum azole antifungals and a clinically useful alternative to voriconazole for the treatment of invasive aspergillosis. It may also prove useful for the treatment of candidemia and invasive mold infections; however, these indications await the results of clinical trials.

Recognition of seven species in the Cryptococcus gattii/Cryptococcus neoformans species complex

Phylogenetic analysis of 11 genetic loci and results from many genotyping studies revealed significant genetic diversity with the pathogenic Cryptococcus gattii/Cryptococcus neoformans species complex. Genealogical concordance, coalescence-based, and species tree approaches supported the presence of distinct and concordant lineages within the complex. Consequently, we propose to recognize the current C. neoformans var. grubii and C. neoformans var. neoformans as separate species, and five species within C. gattii. The type strain of C. neoformans CBS132 represents a serotype AD hybrid and is replaced. The newly delimited species differ in aspects of pathogenicity, prevalence for patient groups, as well as biochemical and physiological aspects, such as susceptibility to antifungals. MALDI-TOF mass spectrometry readily distinguishes the newly recognized species.

Safety and pharmacokinetics of isavuconazole as antifungal prophylaxis in acute myeloid leukemia patients with neutropenia: results of a phase 2, dose escalation study

Isavuconazole is a novel broad-spectrum triazole antifungal agent. This open-label dose escalation study assessed the safety and pharmacokinetics of intravenous isavuconazole prophylaxis in patients with acute myeloid leukemia who had undergone chemotherapy and had preexisting/expected neutropenia. Twenty-four patients were enrolled, and 20 patients completed the study. The patients in the low-dose cohort (n = 11) received isavuconazole loading doses on day 1 (400/200/200 mg, 6 h apart) and day 2 (200/200 mg, 12 h apart), followed by once-daily maintenance dosing (200 mg) on days 3 to 28. The loading and maintenance doses were doubled in the high-dose cohort (n = 12). The mean ± standard deviation plasma isavuconazole areas under the concentration-time curves for the dosing period on day 7 were 60.1 ± 22.3 μg · h/ml and 113.1 ± 19.6 μg · h/ml for the patients in the low-dose and high-dose cohorts, respectively. The adverse events in five patients in the low-dose cohort and in eight patients in the high-dose cohort were considered to be drug related. Most were mild to moderate in severity, and the most common adverse events were headache and rash (n = 3 each). One patient in the high-dose cohort experienced a serious adverse event (unrelated to isavuconazole treatment), and two patients each in the low-dose and high-dose cohorts discontinued the study due to adverse events. Of the 20 patients who completed the study, 18 were classified as a treatment success. In summary, the results of this analysis support the safety and tolerability of isavuconazole administered at 200 mg and 400 mg once-daily as prophylaxis in immunosuppressed patients at high risk of fungal infections. (This study is registered at ClinicalTrials.gov under registration number NCT00413439.).

Skeletal cryptococcosis from 1977 to 2013

Skeletal cryptococcosis, an aspect of disseminated cryptococcal disease or isolated skeletal cryptococcal infection, is a rare but treatable disease. However, limited information is available regarding its clinical features, treatment, and prognosis. This systematic review examined all cases published between April 1977 and May 2013 with regard to the factors associated with this disease, including patient sex, age, and epidemiological history; affected sites; clinical symptoms; underlying diseases; laboratory tests; radiological manifestations; and delays in diagnosis, treatment, follow-up assessments, and outcomes. We found that immune abnormality is a risk factor but does not predict mortality; these observations are due to recent Cryptococcus neoformans var gattii (CNVG) outbreaks (Chaturvedi and Chaturvedi, 2011). Dissemination was irrespective of immune status and required combination therapy, and dissemination carried a worse prognosis. Therefore, a database of skeletal cryptococcosis cases should be created.

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

Epidemiological cutoff values (ECVs) of isavuconazole are not available for Cryptococcus spp. The isavuconazole ECVs based on wild-type (WT) MIC distributions for 438 Cryptococcus neoformans nongenotyped isolates, 870 isolates of genotype VNI, and 406 Cryptococcus gattii isolates from six laboratories and different geographical areas were 0.06, 0.12, and 0.25 μg/ml, respectively. These ECVs may aid in detecting non-WT isolates with reduced susceptibilities to isavuconazole.

Phenotypic differences of Cryptococcus molecular types and their implications for virulence in a Drosophila model of infection

Compared to Cryptococcus neoformans, little is known about the virulence of the molecular types in Cryptococcus gattii. We compared in vitro virulence factor production and survival data using a Drosophila model of infection to further characterize the phenotypic features of different cryptococcal molecular types. Forty-nine different isolates were inoculated into wild-type flies and followed for survival. In vitro, isolates were assessed for growth at 30 and 37°C, melanin production, capsule size, resistance to H(2)O(2), and antifungal susceptibility. A mediator model was used to assess molecular type and virulence characteristics as predictors of survival in the fly model. VGIII was the most virulent molecular type in flies (P < 0.001). At 30°C, VGIII isolates grew most rapidly; at 37°C, VNI isolates grew best. C. gattii capsules were larger than those of C. neoformans (P < 0.001). Mediator model analysis found a strong correlation of Drosophila survival with molecular type and with growth at 30°C. We found molecular-type-specific differences in C. gattii in growth at different temperatures, melanin production, capsule size, ability to resist hydrogen peroxide, and antifungal susceptibility, while growth at 30°C and the VGIII molecular type were strongly associated with virulence in a Drosophila model of infection.