A multicentre study to optimize echinocandin susceptibility testing of Aspergillus species with the EUCAST methodology and a broth microdilution colorimetric method

Background The determination of the minimal effective concentration (MEC) of echinocandins against Aspergillus species is subjective, time consuming and has been associated with very major errors. Methods The MECs/MICs of 40 WT [10 each of Aspergillus fumigatus species complex (SC), Aspergillus flavus SC, Aspergillus terreus SC and Aspergillus niger SC] and 4 non-WT A. fumigatus isolates were determined with EUCAST E.Def 9.3.1 read microscopically, macroscopically, spectrophotometrically and colorimetrically in three centres. The optimal conditions for spectrophotometric (single- versus multi-point readings) and colorimetric (XTT/menadione concentration and stability, incubation time) methods were evaluated in preliminary studies using different cut-offs for the determination of macroscopic, spectrophotometric and colorimetric MIC endpoints compared with the microscopically determined MEC. Inter-centre and inter-method essential (within one 2-fold dilution) agreement (EA) and categorical agreement (CA) were determined. Results Both macroscopic and spectrophotometric endpoint readings showed poor inter-centre EA (53%–66%) and low CA (41%–88%) in distinguishing WT from non-WT A. fumigatus SC isolates, while significant differences compared with the microscopic MECs were observed for all echinocandins (EA 6%–54%). For the colorimetric method, the optimal conditions were 400 mg/L XTT/6.25 μΜ menadione, incubation for 1–2 h until the drug-free control reached an absorbance at 450/630 nm of >0.8 and use of 50% inhibition of XTT conversion as a cut-off for all species and echinocandins. All non-WT isolates had high XTT MICs >1 mg/L, whereas the overall inter-centre EA and CA were 72%–89% and 100%, respectively. Conclusions The XTT colorimetric assay improved the antifungal susceptibility testing of echinocandins against Aspergillus spp., reliably detecting non-WT isolates.

Development and multicentre validation of an agar-based screening method for echinocandin susceptibility testing of Aspergillus species

Background Reference antifungal susceptibility testing of echinocandins against Aspergillus spp. relies on the determination of the minimal effective concentration, which is difficult to perform, time-consuming and subjective. We developed and evaluated in a multicentre study an agar-based screening method for echinocandin susceptibility testing of Aspergillus spp. Methods Forty WT isolates [10 Aspergillus fumigatus species complex (SC), 10 Aspergillus flavus SC, 10 Aspergillus terreus SC and 10 Aspergillus niger SC] and 4 non-WT A. fumigatus isolates with or without known fks alterations were used. The optimal test conditions and stability over time were evaluated in preliminary studies monitoring colony growth. Twenty-microlitre aliquots of 1–2 McFarland inocula in 0.1% Tween 20 aqueous solution were added to each well and plates were incubated for 24/48 h at 35 ± 2°C. Subsequently, all isolates were tested blindly at three centres using four-well screening plates, containing anidulafungin, caspofungin, micafungin or no antifungal in each of the four wells, respectively. Results WT isolates produced fluffy colonies on drug-free agar wells only. The non-WT isolates produced fluffy colonies on echinocandin-containing and control agar wells. Using the echinocandin concentrations of 0.25 mg/L anidulafungin, 1 mg/L caspofungin and 0.125 mg/L micafungin, and the compact (non-fluffy) versus fluffy colony morphology endpoint, all centres successfully discriminated non-WT and WT strains even after 24 h. Among the three echinocandins, anidulafungin produced the clearest endpoints. Conclusions The four-well plate agar method is suitable for echinocandin susceptibility screening of Aspergillus spp. and can be used to detect echinocandin non-WT isolates.

Paenidigyamycin A, Potent Antiparasitic Imidazole Alkaloid from the Ghanaian Paenibacillus sp. DE2SH

A new alkaloid paenidigyamycin A (1) was obtained from the novel Ghanaian Paenibacillus sp. isolated from the mangrove rhizosphere soils of the Pterocarpus santalinoides tree growing in the wetlands of the Digya National Park, Ghana. Compound 1 was isolated on HPLC at tR = 37.0 min and its structure determined by MS, 1D, and 2D-NMR data. When tested against L. major, 1 (IC50 0.75 µM) was just as effective as amphotericin B (IC50 0.31 µM). Against L. donovani, 1 (IC50 7.02 µM) was twenty-two times less active than amphotericin B (IC50 0.32 µM), reinforcing the unique effectiveness of 1 against L. major. For T. brucei brucei, 1 (IC50 0.78 µM) was ten times more active than the laboratory standard Coptis japonica (IC50 8.20 µM). The IC50 of 9.08 µM for 1 against P. falciparum 3d7 compared to artesunate (IC50 36 nM) was not strong, but this result suggests the possibility of using the paenidigyamycin scaffold for the development of potent antimalarial drugs. Against cercariae, 1 showed high anticercaricidal activity compared to artesunate. The minimal lethal concentration (MLC) and minimal effective concentration (MEC) of the compound were 25 and 6.25 µM, respectively, while artesunate was needed in higher quantities to produce such results. However, 1 (IC50 > 100 µM) was not active against T. mobilensis.

Pharmacokinetic Properties of Adenosine Amine Congener in Cochlear Perilymph after Systemic Administration

Noise-induced hearing loss (NIHL) is a global health problem affecting over 5% of the population worldwide. We have shown previously that acute noise-induced cochlear injury can be ameliorated by administration of drugs acting on adenosine receptors in the inner ear, and a selective A1adenosine receptor agonist adenosine amine congener (ADAC) has emerged as a potentially effective treatment for cochlear injury and resulting hearing loss. This study investigated pharmacokinetic properties of ADAC in rat perilymph after systemic (intravenous) administration using a newly developed liquid chromatography-tandem mass spectrometry detection method. The method was developed and validated in accordance with the USA FDA guidelines including accuracy, precision, specificity, and linearity. Perilymph was sampled from the apical turn of the cochlea to prevent contamination with the cerebrospinal fluid. ADAC was detected in cochlear perilymph within two minutes following intravenous administration and remained in perilymph above its minimal effective concentration for at least two hours. The pharmacokinetic pattern of ADAC was significantly altered by exposure to noise, suggesting transient changes in permeability of the blood-labyrinth barrier and/or cochlear blood flow. This study supports ADAC development as a potential clinical otological treatment for acute sensorineural hearing loss caused by exposure to traumatic noise.

Substoichiometric inhibition of transthyretin misfolding by immune-targeting sparsely populated misfolding intermediates: a potential diagnostic and therapeutic for TTR amyloidoses

Wild-type and mutant transthyretin (TTR) can misfold and deposit in the heart, peripheral nerves, and other sites causing amyloid disease. Pharmacological chaperones, Tafamidis® and diflunisal, inhibit TTR misfolding by stabilizing native tetrameric TTR; however, their minimal effective concentration is in the micromolar range. By immune-targeting sparsely populated TTR misfolding intermediates (i.e. monomers), we achieved fibril inhibition at substoichiometric concentrations. We developed an antibody (misTTR) that targets TTR residues 89–97, an epitope buried in the tetramer but exposed in the monomer. Nanomolar misTTR inhibits fibrillogenesis of misfolded TTR under micromolar concentrations. Pan-specific TTR antibodies do not possess such fibril inhibiting properties. We show that selective targeting of misfolding intermediates is an alternative to native state stabilization and requires substoichiometric concentrations. MisTTR or its derivative may have both diagnostic and therapeutic potential.

Effects of Microtubule Stabilization by Epothilone B Depend on the Type and Age of Neurons

Several studies have demonstrated the therapeutic potential of applying microtubule- (MT-) stabilizing agents (MSAs) that cross the blood-brain barrier to promote axon regeneration and prevent axonal dystrophy in rodent models of spinal cord injury and neurodegenerative diseases. Paradoxically, administration of MSAs, which have been widely prescribed to treat malignancies, is well known to cause debilitating peripheral neuropathy and axon degeneration. Despite the growing interest of applying MSAs to treat the injured or degenerating central nervous system (CNS), consequences of MSA exposure to neurons in the central and peripheral nervous system (PNS) have not been thoroughly investigated. Here, we have examined and compared the effects of a brain-penetrant MSA, epothilone B, on cortical and sensory neurons in culture and show that epothilone B exhibits both beneficial and detrimental effects, depending on not only the concentration of drug but also the type and age of a neuron, as seen in clinical settings. Therefore, to exploit MSAs to their full benefit and minimize unwanted side effects, it is important to understand the properties of neuronal MTs and strategies should be devised to deliver minimal effective concentration directly to the site where needed.

A Prospective, Self-Controlled and Randomized Study about the Optimal Timing of Leucovorin Rescue after High Dose Methotrexate Management

Background and objectives: Methotrexate (MTX) is a folic acid reductase inhibitor widely used. Peripheral infusion of high dose MTX (HD-MTX) could prevent the central nervous system recurrence of leukemia and NHL. Due to the blood brain barrier, only 1-3% of MTX in the peripheral blood can enter the cerebrospinal fluid. Improving the peripheral MTX drug dosage helps to improve MTX concentration in the cerebrospinal fluid. However, high concentration of MTX has serious side effects to normal organs. Leucovorin (CF) rescue is given to reduce the toxic effect of methotrexate on normal cells. During high dose MTX therapy, monitoring of serum concentration of MTX and timely CF rescue therapy are mandatory so as to maximum the efficacy of MTX and minimize the toxicities. Due to the lack of randomized clinical trials with large sample, the safe dose and most appropriate time of leucovorin rescue treatment are of no consensus. In order to study the effect of different time of leucovorin rescue treatment on the serum concentration of MTX, we carried out this study. Patients and methods: We included patients who had pathological diagnosis of non-Hodgkin's lymphoma and indications to receive HD-MTX as single agent or component in combined regimen consecutively from October 2011 to June 2014 at our hospital. Patients were randomized to receive CF rescue at the sixth hour after MTX infusion in the first course and twelfth hour in the second course or the twelfth hour in the first course and sixth hour in the second course. A dosage of 3.5 g/m2 of MTX was provided. Adequate hydration, alkalization and monitoring of laboratory tests were administered. Intrathecal injection of MTX plus cytarabine and dexamethasone were given after MTX infusion. 100mg of CF was given at the first time, then 30mg of CF were given every 6 hours for a total of 7 times until the plasma concentration of MTX were lower than 1×10-7 mol/L. Blood samples were collected at 2, 12, 18, 24, 28, 72 hours after the beginning of MTX infusion. High performance liquid chromatography was used to test the plasma concentration of MTX. Results: There were 23 male patients and 12 female patients with a mean age of 41 years. Most of patients were diagnosed as diffuse large B cell lymphoma (65.7%). Eleven cases (31.4%) had central nervous system invasion at the time of HD-MTX treatment. Twenty-one patients (51%) had more than one extra-nodal lesion. Sixteen patients were randomly to be rescued at the sixth hour in the first course then the twelfth hour in the second course. Nineteen patients were randomly to be rescued at the twelfth hour in the first course then the sixth hour in the second course. The plasma concentration of MTX of patients rescued at the sixth hour at the time of 2, 12, 18, 24, 48 hours were 5.21±0.36×10-5 mol/L, 8.01±0.635×10-5 mol/L, 4.57±1.67×10-6 mol/L, 1.43±0.83×10-6 mol/L, 0.1±0.1×10-6 mol/L, respectively; The plasma concentration MTX of patients rescued at the twelfth hour at the time of 2, 12, 18, 24, 48 hours were 5.46±0.34×10-5 mol/L, 8.65±0.663×10-5 mol/L, 5.4±0.93×10-6 mol/L, 1.12±0.21×10-6 mol/L, 0.1±0.24×10-6 mol/L, respectively. There was no significant difference of MTX concentration level between patients treated with different CF rescue timing, P >0.05. Most of patients achieved maximal MTX concentration at the twelfth hour, and descended to be lower than the minimal effective concentration at the eighteenth hour. At the forty-eighth hour, majority of patients had MTX concentration being in a safe range. The rate of grade 3 to 4 adverse reactions including neutropenia, anemia, thrombocytopenia and grade 1 to 2 side effects including neutropenia, thrombocytopenia, mucositis, fatigue, and MTX discharge delay were higher when patients were rescued with CF at the twelfth hour, though P >0.05. Conclusion: Most of patients treated with high dose MTX reached the maximum MTX concentration at the twelfth hour after MTX infusion, and descended to be under the minimal effective concentration at the eighteenth hour, then to be in the safe range at the forty eighth hour. No significant difference of MTX concentration was found between patients rescued with CF at the sixth hour or the twelfth hour. However, adverse reactions were lower when patients were treated with CF rescue at the sixth hour. It seems a better choice to give patients CF rescue at the sixth hour after MTX infusion. Disclosures No relevant conflicts of interest to declare.

In VitroActivities of a Wide Panel of Antifungal Drugs against Various Scopulariopsis and Microascus Species

ABSTRACTThein vitroactivities of 11 antifungal drugs against 68ScopulariopsisandMicroascusstrains were investigated. Amphotericin B, 5-fluorocytosine, fluconazole, itraconazole, ketoconazole, miconazole, posaconazole, voriconazole, and ciclopirox showed no or poor antifungal effect. The best activities were exhibited by terbinafine and caspofungin, where the MIC and MEC (minimal effective concentration) ranges were 0.0313 to >16 μg/ml and 0.125 to 16 μg/ml, respectively. The MIC and MEC modes were both 1 µg/ml for terbinafine and caspofungin; the MIC50and MEC50were 1 µg/ml for both drugs, whereas the MIC90and MEC90were 4 µg/ml and 16 µg/ml, respectively.

Evaluation of a Modified EUCAST Fragmented-Mycelium Inoculum Method forIn VitroSusceptibility Testing of Dermatophytes and the Activity of Novel Antifungal Agents

ABSTRACTFor antifungal susceptibility testing of nonsporulating or poorly sporulating dermatophytes, a fragmented-mycelium inoculum preparation method was established and compared to broth microdilution testing according to CLSI and EUCAST guidelines. Moreover, thein vitroactivity of new antifungal agents against dermatophytes was evaluated. Agreement between the mycelial inoculum method and the CLSI broth microdilution method was high (93% to 100%). Echinocandins (minimal effective concentration [MEC], ≤0.5 mg/liter) and posaconazole (MIC, ≤3.00 mg/liter) showed good activity against all tested dermatophytes.