The Mechanism of Antifungal Action of Essential Oil from Dill (Anethum graveolens L.) on Aspergillus flavus

The essential oil extracted from the seeds of dill (Anethum graveolens L.) was demonstrated in this study as a potential source of an eco-friendly antifungal agent. To elucidate the mechanism of the antifungal action further, the effect of the essential oil on the plasma membrane and mitochondria of Aspergillus flavus was investigated. The lesion in the plasma membrane was detected through flow cytometry and further verified through the inhibition of ergosterol synthesis. The essential oil caused morphological changes in the cells of A. flavus and a reduction in the ergosterol quantity. Moreover, mitochondrial membrane potential (MMP), acidification of external medium, and mitochondrial ATPase and dehydrogenase activities were detected. The reactive oxygen species (ROS) accumulation was also examined through fluorometric assay. Exposure to dill oil resulted in an elevation of MMP, and in the suppression of the glucose-induced decrease in external pH at 4 µl/ml. Decreased ATPase and dehydrogenase activities in A. flavus cells were also observed in a dose-dependent manner. The above dysfunctions of the mitochondria caused ROS accumulation in A. flavus. A reduction in cell viability was prevented through the addition of L-cysteine, which indicates that ROS is an important mediator of the antifungal action of dill oil. In summary, the antifungal activity of dill oil results from its ability to disrupt the permeability barrier of the plasma membrane and from the mitochondrial dysfunction-induced ROS accumulation in A. flavus

Target protection as a key antibiotic resistance mechanism

Antibiotic resistance is mediated through several distinct mechanisms, most of which are relatively well understood and the clinical importance of which has long been recognized. Until very recently, neither of these statements was readily applicable to the class of resistance mechanism known as target protection, a phenomenon whereby a resistance protein physically associates with an antibiotic target to rescue it from antibiotic-mediated inhibition. In this Review, we summarize recent progress in understanding the nature and importance of target protection. In particular, we describe the molecular basis of the known target protection systems, emphasizing that target protection does not involve a single, uniform mechanism but is instead brought about in several mechanistically distinct ways

Quality Control and Reference Guidelines for CLSI Broth Microdilution Method (M38-A Document) for Susceptibility Testing of Anidulafungin against Molds▿

The CLSI (formerly NCCLS) M38-A document for antifungal susceptibility testing of filamentous fungi does not describe guidelines for echinocandins. A multicenter study (eight centers) evaluated inter- and intralaboratory reproducibilities of two reading times (24 and 48 h or 48 and 72 h) and two end points (MICs and minimum effective concentrations [MECs]) for evaluating anidulafungin against molds. Anidulafungin MICs (≥50% inhibition) and MECs (morphological hyphal changes) were determined for seven Aspergillus isolates (four species) and one isolate each of Fusarium moniliforme, Fusarium solani, and Paecilomyces variotii and for two Scedosporium apiospermum isolates. The inter- and intralaboratory reproducibilities of 10 replicate tests performed in each laboratory on 10 different days for each isolate was 100% at 24 h (MECs, ≤0.015 μg/ml) for six Aspergillus and P. variotii isolates. The reproducibility was 94 to 96.7% at 72 h (MECs, 1 to 8 μg/ml) for S. apiospermum and 96.7 to 97.5% at 48 h (MICs, ≥32 μg/ml) for both Fusarium isolates. Introduction of these identified optimum testing conditions for anidulafungin into future versions of the M38 document is warranted