Micafungin in the treatment of invasive candidiasis and invasive aspergillosis

Micafungin is an echinocandin antifungal agent available for clinical use in Japan, Europe, and the United States. Through inhibition of β-1,3-glucan production, an essential component of the fungal cell wall, micafungin exhibits potent antifungal activity against key pathogenic fungi, including Candida and Aspergillus species, while contributing minimal toxicity to mammalian cells. This activity is maintained against polyene and azole-resistant isolates. Pharmacokinetic and pharmacodynamic studies have demonstrated linear kinetics both in adults and children with concentration-dependent activity observed both in vitro and in vivo. Dosage escalation studies have also demonstrated that doses much higher than those currently recommended may be administered without serious adverse effects. Clinically, micafungin has been shown to be efficacious for the treatment of invasive candidiasis and invasive aspergillosis. Furthermore, the clinical effectiveness of micafungin against these infections occurs without the drug interactions that occur with the azoles and the nephrotoxicity observed with amphotericin B formulations. This review will focus on the pharmacology, clinical microbiology, mechanisms of resistance, safety, and clinical efficacy of micafungin in the treatment of invasive candidiasis and invasive aspergillosis

Compensatory response of the cell wall integrity pathway and chitin to caspofungin exposure in Candida glabrata

Background: Studies in Saccharomyces cerevisiae and Candida albicans have reported an up-regulation of the cell wall integrity pathway and an increase in cell wall chitin following caspofungin exposure. This study sought to examine the genetic and phenotypic response of the emerging fungal pathogen Candida glabrata to caspofungininduced cell wall damage. Methods: Antifungal susceptibility testing was performed using Saccharomyces cerevisiae deletion strains to identify genes affecting caspofungin activity. Bioinformatics (tBLASTn) searches were used to identify homologs of these sequences in C. glabrata. The XTT colorimetric viability assay and time-kill studies were used to assess the phenotypic response of wild-type C. glabrata ATCC 200989 and the corresponding (Delta symbol)slt2 gene knockout strain to caspofungin. Following caspofungin challenge, relative gene expression of SLT2 (a mitogen-activated protein kinase of the cell wall integrity pathway), CHS3 (chitin synthase III), and SKT5 (activator of chitin synthase III) was determined in triplicate using reverse-transcriptase real-time PCR. Chitin was quantified in triplicate using a colorimetric assay. Results: SLT2, CHS3 and SKT5 deletion in S. cerevisiae resulted in enhanced caspofungin activity. Each of these genes was found to have a homologous region within the C. glabrata genome. Fungal viability of wild-type C. glabrata ATCC 200989 did not fall below 16.3% viability following any caspofungin concentration. In contrast, no viable cells were present in the C. glabrata (Delta symbol)slt2 mutant strain at caspofungin concentrations (Greater than or equal to)0.25 mcg/mL. Similarly, time-kill results demonstrated that caspofungin was only fungicidal against the C. glabrata (Delta symbol)slt2 strain at concentrations of 1 and 16 mcg/mL. Relative gene expression of SLT2, CHS3 and SKT5 increased 2- to 4-fold following caspofungin exposure in wildtype C. glabrata. In addition, chitin content increased 3- to 4.5-fold in wild-type C. glabrata following all caspofungin concentrations tested. In the C. glabrata (Delta symbol)slt2 strain, CHS3 expression and chitin content did not increase following caspofungin challenge. Conclusions: Caspofungin was not fungicidal against the wild-type C. glabrata strain and gene expression of SLT2, CHS3 and SKT5 increased in response to caspofungininduced cell wall damage. Additionally, chitin content was elevated following caspofungin exposure in wild-type C. glabrata. In the corresponding C. glabrata strain with a deletion in SLT2 (a key component of the cell wall integrity pathway) caspofungin activity was significantly enhanced. Also, gene expression of CHS3 and chitin content were not elevated with increasing caspofungin concentrations. This suggests a link between the cell wall integrity pathway, increased chitin concentrations and the decreased caspofungin potency in C. glabrata.Pharmac

Once-Daily Amikacin Dosing in Burn Patients Treated with Continuous Venovenous Hemofiltration▿

Amikacin clearance can be increased in burn injury, which is often complicated by renal insufficiency. Little is known about the impact of renal replacement therapies, such as continuous venovenous hemofiltration (CVVH), on amikacin pharmacokinetics. We retrospectively examined the clinical pharmacokinetics, bacteriology, and clinical outcomes of 60 burn patients given 15 mg/kg of body weight of amikacin in single daily doses. Twelve were treated with concurrent CVVH therapy, and 48 were not. The pharmacodynamic target of ≥10 for the maximum concentration of drug in serum divided by the MIC (Cmax/MIC) was achieved in only 8.5% of patients, with a small reduction of Cmax in patients receiving CVVH and no difference in amikacin clearance. Mortality and burn size were greater in patients who received CVVH. Overall, 172 Gram-negative isolates were recovered from the blood cultures of 39 patients, with amikacin MIC data available for 82 isolates from 24 patients. A 10,000-patient Monte Carlo simulation was conducted incorporating pharmacokinetic and MIC data from these patients. The cumulative fraction of response (CFR) was similar in CVVH and non-CVVH patients. The CFR rates were not significantly improved by a theoretical 20 mg/kg amikacin dose. Overall, CVVH did not appear to have a major impact on amikacin serum concentrations. The low pharmacodynamic target attainment appears to be primarily due to higher amikacin MICs rather than more rapid clearance of amikacin related to CVVH therapy

Comparing plant–insect trophic transfer of Cu from lab-synthesised nano-Cu(OH)2 with a commercial nano-Cu(OH)2 fungicide formulation

To examine whether studies conducted with highly purified, laboratory-synthesised nanomaterials are predictive of behaviour of commercial nanopesticide formulations, we studied the trophic transfer of Cu(OH)2 manufactured nanomaterials (MNMs) by tobacco hornworms (Manduca sexta) feeding on surface-treated tomato leaves (Solanum lycopersicum).We compared laboratory-synthesised copper(II) hydroxide (Cu(OH)2) nanowire with the widely used fungicide Kocide 3000, whose active ingredient is nano-needles of copper(II) hydroxide (nCu(OH)2). All leaves were treated at rates in accordance with the product label (1.5 kg ha 1 or 150 mgm 2). As a control, we used highly soluble CuSO4. Over the course of the study (exposure up to 7 days followed by up to 20 days of elimination), hornworms accumulated Cu from all three treatments far exceeding controls (ranging from,55 to 105 times greater for nCu(OH)2 and CuSO4 respectively). There were also significant differences in accumulation of Cu among treatments, with the greatest accumulation in the CuSO4 treatment (up to 105 18 mg Cu per g dry mass) and the least in the nCu(OH)2 treatment (up to 55 12 mg Cu per g dry mass. The difference in their toxicity and accumulation and elimination dynamics was found to be correlated with the solubility of the materials in the exposure suspensions (r2¼0.99). We also found that first-instar larvae are more susceptible to toxicity from all forms of Cu than second-instar larvae. Our results provide valuable knowledge on whether the ecotoxicity of commercial MNM products such as Kocide can be compared with laboratory-synthesised counterparts and suggests that predictions can be made based on functional assays such as measurement of solubility.publishe

High resolution studies of the Afa/Dr adhesin DraE and its interaction with chloramphenicol.

Pathogenic Escherichia coli expressing Afa/Dr adhesins are able to cause both urinary tract and diarrheal infections. The Afa/Dr adhesins confer adherence to epithelial cells via interactions with the human complement regulating protein, decay accelerating factor (DAF or CD55). Two of the Afa/Dr adhesions, AfaE-III and DraE, differ from each other by only three residues but are reported to have several different properties. One such difference is disruption of the interaction between DraE and CD55 by chloramphenicol, whereas binding of AfaE-III to CD55 is unaffected. Here we present a crystal structure of a strand-swapped trimer of wild type DraE. We also present a crystal structure of this trimer in complex with chloramphenicol, as well as NMR data supporting the binding position of chloramphenicol within the crystal. The crystal structure reveals the precise atomic basis for the sensitivity of DraE-CD55 binding to chloramphenicol and demonstrates that in contrast to other chloramphenicol-protein complexes, drug binding is mediated via recognition of the chlorine "tail" rather than via intercalation of the benzene rings into a hydrophobic pocket