Therapeutic Potential of Fosmanogepix (APX001) for Intra-abdominal Candidiasis: from Lesion Penetration to Efficacy in a Mouse Model.

Intra-abdominal candidiasis (IAC) is one of the most common yet underappreciated forms of invasive candidiasis. IAC is difficult to treat, and therapeutic failure and drug-resistant breakthrough infections are common in some institutions despite the use of echinocandins as first-line agents. Fosmanogepix (FMGX, formerly APX001) is a first-in-class antifungal prodrug that can be administered both intravenously and orally. FMGX is currently in phase 2 clinical development for the treatment of life-threatening invasive fungal infections. To explore the pharmacological properties and therapeutic potential of FMGX for IAC, we evaluated both drug penetration and efficacy of the active moiety manogepix (MGX, formerly APX001A) in liver tissues in a clinically relevant IAC mouse model infected with Candida albicans Matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) and laser capture microdissection (LCM)-directed absolute drug quantitation were employed to evaluate drug penetration into liver abscess lesions both spatially and quantitatively. The partitioning of MGX into lesions occurred slowly after a single dose; however, robust accumulation in the lesion was achieved after 3 days of repeated dosing. Associated with this drug penetration pattern, reduction in fungal burden and clearance in the liver were observed in mice receiving the multiday FMGX regimen. In comparison, administration of micafungin resulted in marginal reduction in fungal burden at the end of 4 days of treatment. These results suggest that FMGX is a promising candidate for the treatment of IAC.

Comparative Pharmacodynamics of Echinocandins against Aspergillus fumigatus Using an In Vitro Pharmacokinetic/Pharmacodynamic Model That Correlates with Clinical Response to Caspofungin Therapy: Is There a Place for Dose Optimization?

Echinocandins have been used as primary therapy of invasive aspergillosis (IA), with suboptimal results at standard dosing. Here, we explored the efficacy of dose escalation in a validated in vitro pharmacokinetic/pharmacodynamic (PK/PD) model. Six echinocandin wild-type (WT) and three non-WT A. fumigatus isolates were tested in an in vitro PK/PD model simulating anidulafungin, caspofungin, and micafungin exposures with a free drug maximum concentration (fCmax) of 0.01 to 16 mg/liter and a half-life (t1/2) of 8 to 22 h. The relationship between the area under the dosing interval time-free drug concentration curve (fAUC0-24)/minimum effective concentration (MEC) and % aberrant mycelium formation was analyzed. PK/PD indices associated with 50 to 99.99% maximal activity (EI50 to EI99.99) were correlated with the clinical outcome of a 50-mg/day standard dose of caspofungin. The probability of target attainment (PTA) was calculated for different dosing regimens of each echinocandin via Monte Carlo analysis. A sigmoidal PK/PD relationship was found for WT isolates with EI99 values of 766, 8.8, and 115 fAUC0-24/CLSI MEC for anidulafungin, caspofungin, and micafungin, respectively. No aberrant mycelia were observed for non-WT isolates, irrespective of their MEC and drug exposure. The EI99, EI99.9, and EI99.99 values corresponded to 2-, 3-, and 4-log10 formation of aberrant mycelia and correlated with survival, favorable, and complete response rates to caspofungin primary therapy in patients with IA. A very low PTA (<13%) was found for the standard doses of all echinocandins, whereas a PTA of ≥90% was found with 100 and 150 mg/day of caspofungin and 1,400 mg/day micafungin against WT isolates. For anidulafungin, the PTA for 1,500 mg/day was 10%. Among the three echinocandins, only caspofungin at 2 or 3 times the licensed dosing was associated with a high PTA. Caspofungin dose escalation might deserve clinical validation.

Low level of antifungal resistance of Candida glabrata blood isolates in Turkey: Fluconazole minimum inhibitory concentration and FKS mutations can predict therapeutic failure.

BACKGROUND: Candida glabrata is the third leading cause of candidaemia in Turkey; however, the data regarding antifungal resistance mechanisms and genotypic diversity in association with their clinical implication are limited. OBJECTIVES: To assess genotypic diversity, antifungal susceptibility and mechanisms of drug resistance of C glabrata blood isolates and their association with patients' outcome in a retrospective multicentre study. PATIENTS/METHODS: Isolates from 107 patients were identified by ITS sequencing and analysed by multilocus microsatellite typing, antifungal susceptibility testing, and sequencing of PDR1 and FKS1/2 hotspots (HSs). RESULTS: Candida glabrata prevalence in Ege University Hospital was twofold higher in 2014-2019 than in 2005-2014. Six of the analysed isolates had fluconazole MICs ≥ 32 µg/mL; of them, five harboured unique PDR1 mutations. Although echinocandin resistance was not detected, three isolates had mutations in HS1-Fks1 (S629T, n = 1) and HS1-Fks2 (S663P, n = 2); one of the latter was also fluconazole-resistant. All patients infected with isolates carrying HS-FKS mutations and/or demonstrating fluconazole MIC ≥ 32 µg/mL (except one without clinical data) showed therapeutic failure (TF) with echinocandin and fluconazole; seven such isolates were collected in Ege (n = 4) and Gulhane (n = 3) hospitals and six detected recently. Among 34 identified genotypes, none were associated with mortality or enriched for fluconazole-resistant isolates. CONCLUSION: Antifungal susceptibility testing should be supplemented with HS-FKS sequencing to predict TF for echinocandins, whereas fluconazole MIC ≥ 32 µg/mL may predict TF. Recent emergence of C glabrata isolates associated with antifungal TF warrants future comprehensive prospective studies in Turkey.

Ceftazidime-Avibactam in Combination With Fosfomycin: A Novel Therapeutic Strategy Against Multidrug-Resistant Pseudomonas aeruginosa.

Previously, by targeting penicillin-binding protein 3, Pseudomonas-derived cephalosporinase (PDC), and MurA with ceftazidime-avibactam-fosfomycin, antimicrobial susceptibility was restored among multidrug-resistant (MDR) Pseudomonas aeruginosa. Herein, ceftazidime-avibactam-fosfomycin combination therapy against MDR P. aeruginosa clinical isolate CL232 was further evaluated. Checkerboard susceptibility analysis revealed synergy between ceftazidime-avibactam and fosfomycin. Accordingly, the resistance elements present and expressed in P. aeruginosa were analyzed using whole-genome sequencing and transcriptome profiling. Mutations in genes that are known to contribute to ß-lactam resistance were identified. Moreover, expression of blaPDC, the mexAB-oprM efflux pump, and murA were upregulated. When fosfomycin was administered alone, the frequency of mutations conferring resistance was high; however, coadministration of fosfomycin with ceftazidime-avibactam yielded a lower frequency of resistance mutations. In a murine infection model using a high bacterial burden, ceftazidime-avibactam-fosfomycin significantly reduced the P. aeruginosa colony-forming units (CFUs), by approximately 2 and 5 logs, compared with stasis and in the vehicle-treated control, respectively. Administration of ceftazidime-avibactam and fosfomycin separately significantly increased CFUs, by approximately 3 logs and 1 log, respectively, compared with the number at stasis, and only reduced CFUs by approximately 1 log and 2 logs, respectively, compared with the number in the vehicle-treated control. Thus, the combination of ceftazidime-avibactam-fosfomycin was superior to either drug alone. By employing a "mechanism-based approach" to combination chemotherapy, we show that ceftazidime-avibactam-fosfomycin has the potential to offer infected patients with high bacterial burdens a therapeutic hope against infection with MDR P. aeruginosa that lack metallo-ß-lactamases.

Molecular Analysis of Resistance and Detection of Non-Wild-Type Strains Using Etest Epidemiological Cutoff Values for Amphotericin B and Echinocandins for Bloodstream Candida Infections from a Tertiary Hospital in Qatar.

A total of 301 Candida bloodstream isolates collected from 289 patients over 5 years at a tertiary hospital in Qatar were evaluated. Out of all Candida infections, 53% were diagnosed in patients admitted to the intensive care units. Steady increases in non-albicans Candida species were reported from 2009 to 2014 (30.2% for Candida albicans versus 69.8% for the other Candida species). Etest antifungal susceptibility testing was performed on all recovered clinical isolates to determine echinocandin (micafungin and anidulafungin) and amphotericin B susceptibilities and assess non-wild-type (non-WT) strains (strains for which MICs were above the epidemiological cutoff values). DNA sequence analysis was performed on all isolates to assess the presence of FKS mutations, which confer echinocandin resistance in Candida species. A total of 3.9% of isolates (12/301) among strains of C. albicans and C. orthopsilosis contained FKS hot spot mutations, including heterozygous mutations in FKS1 For C. tropicalis, the Etest appeared to overestimate strains non-WT for micafungin, anidulafungin, and amphotericin B, as 14%, 11%, and 35% of strains, respectively, had values above the epidemiological cutoff value. However, no FKS mutations were identified in this species. For all other species, micafungin best reported the echinocandin non-WT strains relative to the FKS genotype, as anidulafungin tended to overestimate non-wild-type strains. Besides C. tropicalis, few strains were classified as non-WT for amphotericin B.

Unraveling Drug Penetration of Echinocandin Antifungals at the Site of Infection in an Intra-abdominal Abscess Model.

Intra-abdominal candidiasis (IAC) is a prominent invasive fungal infection associated with high mortality. Prompt antifungal therapy and source control are crucial for successful treatment. Echinocandin antifungal drugs are first-line agents; however, their clinical effectiveness is highly variable, with known potential for breakthrough resistance, and little is known about drug exposure at the site of infection. Using matrix-assisted desorption ionization mass spectrometry imaging technology, we investigated the spatial and quantitative distribution in tissue lesions for two echinocandin drugs, micafungin and CD101, in a clinically relevant IAC mouse model. Drug accumulation within lesions was observed with both drugs at their humanized therapeutic doses. CD101, but not micafungin, accumulated in lesions at levels above the mutant prevention concentration of the infecting strain. These findings indicate that current echinocandin drugs are limited by penetration at the site of infection and have implications for clinical outcomes and emergence of resistance in patients with IAC.

Breakthrough candidaemia caused by phenotypically susceptible Candida spp. in patients with haematological malignancies does not correlate with established interpretive breakpoints.

In a study of 27,864 patients with haematological malignancies, 40 patients with candidaemia were identified, among whom 21 developed candidaemia while receiving systemic antifungal therapy [breakthrough candidaemia (BTC)]. Demographic, clinical, microbiological and molecular features of these episodes were analysed. Compared with 19 patients with de novo candidaemia, patients with BTC were more likely to have neutropenia (81% vs. 63%), longer median duration of neutropenia (27 days vs. 15 days), hypogammaglobulinaemia (62% vs. 37%) and central venous catheters (CVCs) (86% vs. 68%). The median duration of prior antifungal exposure was 46 days (range 3-108 days). Among the 18 available Candida spp. isolates, 15 (83%) were phenotypically susceptible to the antifungal agent that the patient was receiving. Emergence of resistance was the mechanism leading to BTC in three cases of patients receiving echinocandins. Other possible mechanisms of BTC were (i) elevated (≥2) minimum lethal concentration/minimum inhibitory concentration (MLC/MIC) ratio (reduced ability for a fungicidal agent to kill a fungal pathogen) in all patients receiving amphotericin B and (ii) elevated MLC/MIC ratios in all Candida parapsilosis isolates with MICs≤1 µg/mL to echinocandins. DNA sequencing of the hotspot 1 region of the fks1 and fks2 genes in seven different isolates of C. parapsilosis group demonstrated P660A in Fks1 but no polymorphisms in fks2. In conclusion, mechanisms for BTC in the setting of prolonged neutropenia may be host-based (hypogammaglobulinaemia and CVC) and pathogen-based. CLSI interpretive breakpoints do not reliably predict BTC in patients with haematological malignancies and warrant further investigation.

Breakthrough candidemia due to multidrug-resistant Candida glabrata during prophylaxis with a low dose of micafungin.

We identified a case of breakthrough candidemia in a 25-year-old patient receiving micafungin prophylaxis (50 mg/day). Five Candida glabrata isolates were obtained from blood cultures and were classified as multidrug-resistant isolates, since all of them exhibited high MICs for echinocandin and azole drugs. A mutation (S663F) in hot spot 1 of the FKS2 gene was found in all five isolates. This mutation yielded a 1,3-ß-D-glucan synthase enzyme with highly reduced sensitivities to echinocandin drugs.

Pharmacokinetics of posaconazole within epithelial cells and fungi: insights into potential mechanisms of action during treatment and prophylaxis.

BACKGROUND: The antifungal posaconazole concentrates within host cells and protects against Aspergillus fumigatus. The specific subcellular location of posaconazole and the mechanism by which cell-associated posaconazole inhibits fungal growth remain uncharacterized. METHODS: Posaconazole was conjugated with the fluorophore boron-dipyrromethene (BDP-PCZ). A549 pulmonary epithelial cells and A. fumigatus were exposed to BDP-PCZ individually and in coculture. BDP-PCZ subcellular localization and trafficking were observed using confocal microscopy and flow cytometry. RESULTS: BDP-PCZ concentrated within A549 cell membranes, and in particular within the endoplasmic reticulum. Epithelial cell-associated BDP-PCZ rapidly transferred to and concentrated within A. fumigatus cell membranes on contact. BDP-PCZ transfer to conidia did not require phagocytosis and was markedly enhanced by the conidial hydrophobin RodA. Within AF, BDP-PCZ also concentrated in membranes including the endoplasmic reticulum and colocalized with the azole target enzyme CYP51a. Concentration of BDP-PCZ within host and fungal cell membranes persisted for >48 hours and could be competitively inhibited by posaconazole but not voriconazole. CONCLUSIONS: Posaconazole concentrates within host cell membranes and rapidly transfers to A. fumigatus, where it accumulates to high concentrations and persists at the site of its target enzyme. These intracellular and intercellular pharmacokinetic properties probably contribute to the efficacy of PCZ.

Breakthrough invasive candidiasis in patients on micafungin.

For Candida species, a bimodal wild-type MIC distribution for echinocandins exists, but resistance to echinocandins is rare. We characterized isolates from patients with invasive candidiasis (IC) breaking through >or=3 doses of micafungin therapy during the first 28 months of its use at our center: MICs were determined and hot-spot regions within FKS genes were sequenced. Eleven of 12 breakthrough IC cases identified were in transplant recipients. The median duration of micafungin exposure prior to breakthrough was 33 days (range, 5 to 165). Seventeen breakthrough isolates were recovered: FKS hot-spot mutations were found in 5 C. glabrata and 2 C. tropicalis isolates; of these, 5 (including all C. glabrata isolates) had micafungin MICs of >2 microg/ml, but all demonstrated caspofungin MICs of >2 microg/ml. Five C. parapsilosis isolates had wild-type FKS sequences and caspofungin MICs of 0.5 to 1 microg/ml, but 4/5 had micafungin MICs of >2 microg/ml. The remaining isolates retained echinocandin MICs of 2 microg/ml and clinical breakthrough or an alternative mechanism contributes to the nonsusceptible echinocandin MICs in C. parapsilosis requires further study.

Frequency and evolution of Azole resistance in Aspergillus fumigatus associated with treatment failure.

Azoles are the mainstay of oral therapy for aspergillosis. Azole resistance in Aspergillus has been reported infrequently. The first resistant isolate was detected in 1999 in Manchester, UK. In a clinical collection of 519 A. fumigatus isolates, the frequency of itraconazole resistance was 5%, a significant increase since 2004 (p<0.001). Of the 34 itraconazole-resistant isolates we studied, 65% (22) were cross-resistant to voriconazole and 74% (25) were cross-resistant to posaconazole. Thirteen of 14 evaluable patients in our study had prior azole exposure; 8 infections failed therapy (progressed), and 5 failed to improve (remained stable). Eighteen amino acid alterations were found in the target enzyme, Cyp51A, 4 of which were novel. A population genetic analysis of microsatellites showed the existence of resistant mutants that evolved from originally susceptible strains, different cyp51A mutations in the same strain, and microalterations in microsatellite repeat number. Azole resistance in A. fumigatus is an emerging problem and may develop during azole therapy.

Breakthrough Aspergillus fumigatus and Candida albicans double infection during caspofungin treatment: laboratory characteristics and implication for susceptibility testing.

Caspofungin is used for the treatment of acute invasive candidiasis and as salvage treatment for invasive aspergillosis. We report characteristics of isolates of Candida albicans and Aspergillus fumigatus detected in a patient with breakthrough infection complicating severe gastrointestinal surgery and evaluate the capability of susceptibility methods to identify candin resistance. The susceptibility of C. albicans to caspofungin and anidulafungin was investigated by Etest, microdilution (European Committee on Antibiotic Susceptibility Testing [EUCAST] and CLSI), disk diffusion, agar dilution, and FKS1 sequencing and in a mouse model. Tissue was examined by immunohistochemistry, PCR, and sequencing for the presence of A. fumigatus and resistance mutations. The MICs for the C. albicans isolate were as follows: >32 microg/ml caspofungin and 0.5 microg/ml anidulafungin by Etest, 2 microg/ml caspofungin and 0.125 microg/ml anidulafungin by EUCAST methods, and 1 microg/ml caspofungin and 0.5 microg/ml anidulafungin by CLSI methods. Sequencing of the FKS1 gene revealed a mutation leading to an S645P substitution. Caspofungin and anidulafungin failed to reduce kidney CFU counts in animals inoculated with this isolate (P > 0.05 compared to untreated control animals), while both candins completely sterilized the kidneys in animals infected with a control isolate. Disk diffusion and agar dilution methods clearly separated the two isolates. Immunohistochemistry and sequencing confirmed the presence of A. fumigatus without FSK1 resistance mutations in liver and lung tissues. Breakthrough disseminated aspergillosis and candidiasis developed despite an absence of characteristic FKS1 resistance mutations in the Aspergillus isolates. EUCAST and CLSI methodology did not separate the candin-resistant clinical isolate from the sensitive control isolate as well as did the Etest and agar methods.

Reduced Candida glabrata susceptibility secondary to an FKS1 mutation developed during candidemia treatment.

We describe a case of recurring Candida glabrata infection in a 68-year-old African-American female on caspofungin therapy. The initial isolate was susceptible, but isolates recovered during following relapses were not. All isolates were clonal, and high-MIC strains contained a mutation in the highly conserved hot spot 1 region of Fks1p.

Progressive loss of echinocandin activity following prolonged use for treatment of Candida albicans oesophagitis.

OBJECTIVES: To illustrate the progressive loss of cross-echinocandin activity on Candida albicans isolates with strong clonal homology from a patient with advanced HIV infection and chronic oesophagitis progressively resistant to uninterrupted micafungin treatment. METHODS: Antifungal susceptibility profiles for different antifungal agents were determined against serial C. albicans isolates retrieved before and during therapy. Multilocus sequencing typing (MLST) was performed on each of the isolates. FKS1 mutations conferring reduced susceptibility to echinocandin drugs were determined by DNA sequence analysis. RESULTS: Four C. albicans isolates showing identical allelic homology were retrieved from the patient at the initiation and during therapy with micafungin. The progressive lack of clinical response to micafungin therapy was associated with increased MICs of all three echinocandin drugs (caspofungin, micafungin and anidulafungin) in association with the acquisition of mutations in the FKS1 gene. CONCLUSIONS: This report documents for the first time a progressive loss of activity of all three echinocandin drugs against clonally related C. albicans isolates following long-term clinical exposure to this new class of antifungal agents.

Hematogenous infections due to Candida parapsilosis: changing trends in fungemic patients at a comprehensive cancer center during the last four decades.

This study was performed to evaluate trends in species distribution in patients' with hematogenous candidiasis at a comprehensive cancer center. The results of a retrospective analysis from January 1, 1993 to December 31, 1998 were compared with prior reports from Memorial Sloan-Kettering Cancer Center in the last forty years. In 570 total episodes since 1974, 43.9% were due to Candida albicans. During 1990's, C. parapsilosis emerged as the most frequent yeast species in the non-C. albicans group (36.1% during 1993-1998 from 20.9% 1974-1982; p < 0.01). An increase in C. krusei from 5.9% (1974-1982) to 10.5% during the recent six years (1993-1998) was also noticed. The proportion of C. tropicalis among non-albicans fungemia during 1974-1982 was 42.8%, whereas in 1993 to 1998 a marked decline in C. tropicalis hematogenous infection was observed (27.8%; p < 0.01). During 1998, the incidence of candidemia declined from 7.1% (1972-1973) and 6.5% (1982) to 3.4% (p < 0.01), and improved survival among fungemic patients (33% mortality in 1998; 77.3% during 1974-1982; p < 0.001) was encouraging. The increase in C. parapsilosis bloodstream invasion during 1990's was associated with a significant reduction in the endogenous non-albicans Candida tropicalis infection that probably resulted in part due to the common prophylaxis, and/or preemptive fluconazole given routinely in high-risk patients undergoing treatment for cancer. The widespread use of extraneous implantable and/or semi-implantable indwelling intra-vascular devices may also have played an important role in promoting (exogenous) C. parapsilosis infection. This study emphasizes the importance of periodic evaluation of candidemia, especially at centers caring for patients at risk.

Prospective epidemiologic analysis of triazole-resistant nosocomial Candida glabrata isolated from patients at a comprehensive cancer center.

OBJECTIVE: The emergence of Candida glabrata infections among patients with compromised immunity has become a serious concern, especially at centers caring for individuals with cancer. METHODS: During a prospective evaluation of Candida species associated with either clinically significant colonization or infection, 26.9% of C. glabrata isolates showed in vitro resistance to fluconazole (MIC of > or = 64 microg/ml). RESULTS: Antifungal susceptibility profiles and genetic fingerprinting analysis performed by randomly amplified polymorphic DNA (RAPD) techniques confirmed low-probability of phenotypic and genotypic relatedness among nosocomial C. glabrata isolates. CONCLUSIONS: Presence of polyclonal strains of C. glabrata in patients at our hospital was probably related to selection of resistant yeasts from environmental pool rather than monoclonal expansion or clustering of multi-drug resistant C. glabrata in high-risk patients.