烟曲霉的微管蛋白基因鉴定及唑类抗真菌药物的耐药性研究

目的建立烟曲霉临床分离菌株的微管蛋白基因鉴定方法,并分析烟曲霉对唑类抗真菌药物的耐药性。方法对表型鉴定为烟曲霉的菌株,采用十六烷基三甲基溴化铵(CTAB)方法提取烟曲霉菌株DNA,并采用对微管蛋白基因进行PCR扩增和测序的方法对烟曲霉菌株进行分子生物学鉴定,采用琼脂稀释法检测烟曲霉菌株对伊曲康唑和伏立康唑的耐药性。结果 91株临床分离株表型鉴定为烟曲霉,这些菌株在35℃和48℃生长。其中88株(96.70%)经微管蛋白基因鉴定为烟曲霉。87株烟曲霉菌株对4μg/mL伊曲康唑和1μg/mL伏立康唑敏感,检出1株对4μg/mL伊曲康唑和1μg/mL伏立康唑耐药菌株。结论微管蛋白基因鉴定方法可以对烟曲霉进行准确鉴定。     

Mechanism-based pharmacokinetic/pharmacodynamic modeling of the electroencephalogram effects of GABAA receptor modulators: in vitro-in vivo correlations

A mechanism-based pharmacokinetic-pharmacodynamic (PK/PD) model for neuroactive steroids, comprising a separate characterization of 1) the receptor activation process and 2) the stimulus-response relationship, was applied to various nonsteroidal GABAA receptor modulators. The EEG effects of nine prototypical GABAA receptor modulators (six benzodiazepines, one imidazopyridine, one cyclopyrrolone, and one beta-carboline) were determined in rats in conjunction with plasma concentrations. Population PK/PD modeling revealed monophasic concentration-EEG effect relationships with large differences in potency (EC50) and intrinsic activity between the compounds. The data were analyzed on the basis of the mechanism-based PK/PD model for (synthetic) neuroactive steroids on the assumption of a single and unique stimulus-response relationship. The model converged yielding estimates of both the apparent in vivo receptor affinity (KPD) and the in vivo intrinsic efficacy (ePD). The values of KPD ranged from 0.41 +/- 0 ng.ml(-1) for bretazenil to 436 +/- 72 ng.ml(-1) for clobazam and the values for e(PD) from -0.27 +/- 0 for methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate to 0.54 +/- 0.02 for diazepam. Significant linear correlations were observed between KPD for unbound concentrations and the affinity in an in vitro receptor bioassay (r = 0.93) and between e(PD) and the GABA-shift in vitro (r = 0.95). The findings of this investigation show that the in vivo effects of nonsteroidal GABAA receptor modulators and (synthetic) neuroactive steroids can be described on the basis of a single unique transducer function. In this paradigm, the nonsteroidal GABAA receptor modulators behave as partial agonists relative to neuroactive steroids.     

Epidemiological cutoff values for azoles and Aspergillus fumigatus based on a novel mathematical approach incorporating cyp51A sequence analysis

Epidemiological cutoff values (ECV) are commonly used to separate wild-type isolates from isolates with reduced susceptibility to antifungal drugs, thus setting the foundation for establishing clinical breakpoints for Aspergillus fumigatus. However, ECVs are usually determined by eye, a method which lacks objectivity, sensitivity, and statistical robustness and may be difficult, in particular, for extended and complex MIC distributions. We therefore describe and evaluate a statistical method of MIC distribution analysis for posaconazole, itraconazole, and voriconazole for 296 A. fumigatus isolates utilizing nonlinear regression analysis, the normal plot technique, and recursive partitioning analysis incorporating cyp51A sequence data. MICs were determined by using the CLSI M38-A2 protocol (CLSI, CLSI document M38-A2, 2008) after incubation of the isolates for 48 h and were transformed into log(2) MICs. We found a wide distribution of MICs of all azoles, some ranging from 0.02 to 128 mg/liter, with median MICs of 32 mg/liter for itraconazole, 4 mg/liter for voriconazole, and 0.5 mg/liter for posaconazole. Of the isolates, 65% (192 of 296) had mutations in the cyp51A gene, and the majority of the mutants (90%) harbored tandem repeats in the promoter region combined with mutations in the cyp51A coding region. MIC distributions deviated significantly from normal distribution (D'Agostino-Pearson omnibus normality test P value, <0.001), and they were better described with a model of the sum of two Gaussian distributions (R(2), 0.91 to 0.96). The normal plot technique revealed a mixture of two populations of MICs separated by MICs of 1 mg/liter for itraconazole, 1 mg/liter for voriconazole, and 0.125 mg/liter for posaconazole. Recursive partitioning analysis confirmed these ECVs, since the proportions of isolates harboring cyp51A mutations associated with azole resistance were less than 20%, 20 to 30%, and >70% when the MICs were lower than, equal to, and higher than the above-mentioned ECVs, respectively.     

In vivo resistance of a laboratory-selected Aspergillus fumigatus isolate to amphotericin B

The fungal burdens (number of CFU per pair of lungs) in mice infected with Aspergillus fumigatus AB16.4 (for which the amphotericin B [AMB] MIC was elevated) and W73355 (drug-susceptible parent) were reduced by 21 and 81%, respectively, after 5 days of AMB treatment (2 mg/kg/day), indicating that AB16.4 also shows reduced susceptibility to AMB in a murine pulmonary aspergillosis model.     

A comparative study of the post-antifungal effect (PAFE) of amphotericin B, triazoles and echinocandins on Aspergillus fumigatus and Candida albicans

OBJECTIVES: To study the post-antifungal effect (PAFE) of antifungal drugs on Aspergillus fumigatus by a radiometric assay and compare the results with those obtained for Candida albicans. METHODS: A. fumigatus cultures pregrown for 48 h in 96-well microtitre plate were exposed to various concentrations of the antifungal drug for 2 h. The drug-treated mycelia were washed, incubated in RPMI 1640 containing (14)C-labelled amino acids and the accumulation of radioactivity in the mycelia at different time intervals was determined. The PAFE was determined by plotting the amount of radioactivity associated with the mycelia against post-treatment incubation time. The PAFE of antifungal drug on C. albicans was examined by determining the multiplication (cfu/mL) of drug-pretreated cells at different time intervals for 24 h in drug-free medium. RESULTS: Amphotericin B produced a prolonged PAFE (7.5 +/- 0.70 h) against A. fumigatus whereas itraconazole (0.5 +/- 0.0 h), voriconazole (0.5 +/- 0.0 h), posaconazole (0.75 +/- 0.35 h), ravuconazole (0.38 +/- 0.17 h) and the echinocandins caspofungin (< or =0.5 h) and micafungin (< or =0.5 h) produced short PAFE. Short exposure (1 h) of C. albicans to low concentrations (0.125-1 mg/L) of amphotericin B (5.3 +/- 1.15 h), caspofungin (5.6 +/- 0.57 h) and micafungin (5 +/- 1.0 h) produced prolonged PAFE whereas the triazoles produced a short (< or =0.5 h) PAFE. CONCLUSIONS: Determination of (14)C-labelled amino acid accumulation in antifungal drug-pretreated mycelia is a suitable method for studying PAFE in A. fumigatus. Antifungal drugs with fungicidal activity tend to possess longer PAFE compared to fungistatic drugs.     

Itraconazole-amphotericin B antagonism in Aspergillus fumigatus: an E-test-based strategy

We examined an E-test-based strategy for testing the combination of itraconazole and amphotericin B, the latter given either sequentially or concomitantly, in isolates of Aspergillus fumigatus. An antagonistic interaction between the two drugs was noted, especially with the sequential administration of amphotericin B. This in vitro antagonism was reversible.     

Azole Preexposure Affects the Aspergillus fumigatus Population in Patients

The relationship between the azole preexposure of 86 patients and the genotype, azole susceptibility, and cyp51A polymorphisms of 110 corresponding Aspergillus fumigatus isolates was explored. Isolates carrying serial polymorphisms (F46Y and M172V with or without N248T with or without D255E with or without E427K) had higher itraconazole MICs (P = 0.04), although <2 μg/ml using the EUCAST methodology, were associated with two genetic clusters (P < 0.001) and with voriconazole preexposure of patients (P = 0.016). Voriconazole preexposure influences the distribution of A. fumigatus isolates with selection of isolates carrying cyp51A polymorphisms and higher itraconazole MICs.     

Profiling the Aspergillus fumigatus proteome in response to caspofungin

The proteomic response of Aspergillus fumigatus to caspofungin was evaluated by gel-free isobaric tagging for relative and absolute quantitation (iTRAQ) as a means to determine potential biomarkers of drug action. A cell fractionation approach yielding 4 subcellular compartment fractions was used to enhance the resolution of proteins for proteomic analysis. Using iTRAQ, a total of 471 unique proteins were identified in soluble and cell wall/plasma membrane fractions at 24 and 48 h of growth in rich media in a wild-type drug-susceptible strain. A total of 122 proteins showed at least a 2-fold change in relative abundance following exposure to caspofungin (CSF) at just below the minimum effective concentration (0.12 μg/ml). The largest changes were seen in the mitochondrial hypoxia response domain protein (AFUA_1G12250), the level of which decreased >16-fold in the secreted fraction, and ChiA1, the level of which decreased 12.1-fold in the cell wall/plasma membrane fraction. The level of the major allergen and cytotoxin AspF1 was also shown to decrease by 12.1-fold upon the addition of drug. A subsequent iTRAQ analysis of an echinocandin-resistant strain (fks1-S678P) was used to validate proteins specific to drug action. A total of 103 proteins in the 2 fractions tested by iTRAQ were differentially expressed in the wild-type susceptible strain but not significantly changed in the resistant strain. Of these potential biomarkers, 11 had levels that changed at least 12-fold. Microarray analysis of the susceptible strain was performed to evaluate the correlation between proteomics and genomics, with a total of 117 genes found to be changing at least 2-fold. Of these, a total of 22 proteins with significant changes identified by iTRAQ also showed significant gene expression level changes by microarray. Overall, these data have the potential to identify biomarkers that assess the relative efficacy of echinocandin drug therapy.     

Impact of Aspergillus fumigatus in allergic airway diseases

ABSTRACT: For decades, fungi have been recognized as associated with asthma and other reactive airway diseases. In contrast to type I-mediated allergies caused by pollen, fungi cause a large number of allergic diseases such as allergic bronchopulmonary mycoses, rhinitis, allergic sinusitis and hypersensitivity pneumonitis. Amongst the fungi, Aspergillus fumigatus is the most prevalent cause of severe pulmonary allergic disease, including allergic bronchopulmonary aspergillosis (ABPA), known to be associated with chronic lung injury and deterioration in pulmonary function in people with chronic asthma and cystic fibrosis (CF). The goal of this review is to discuss new understandings of host-pathogen interactions in the genesis of allergic airway diseases caused by A. fumigatus. Host and pathogen related factors that participate in triggering the inflammatory cycle leading to pulmonary exacerbations in ABPA are discussed.     

Environmental Isolates of Azole-Resistant Aspergillus fumigatus in Germany

Azole antifungal drug resistance in Aspergillus fumigatus is an emerging problem in several parts of the world. Here we investigated the distribution of such strains in soils from Germany. At a general positivity rate of 12%, most prevalently, we found strains with the TR₃₄/L98H and TR₄₆/Y121F/T289A alleles, dispersed along a corridor across northern Germany. Comparison of the distributions of resistance alleles and genotypes between environment and clinical samples suggests the presence of local clinical clusters.     

Microcalorimetry Assay for Rapid Detection of Voriconazole Resistance in Aspergillus fumigatus

We describe a calorimetric assay for detection of voriconazole-resistant Aspergillus fumigatus within 8 h. Among 27 genetically distinct strains, all 21 resistant and all 6 susceptible strains were correctly identified by measurement of fungal heat production in the presence of voriconazole. This proof-of-concept study demonstrates the potential of microcalorimetry for rapid detection of azole resistance in A. fumigatus.     

提高侵袭性烟曲霉感染痰标本病原学检出率的方法探讨

目的:探讨一种可提高临床痰标本的侵袭性烟曲霉感染检出率的培养基。方法:收集临床常规痰标本分离菌(包括白假丝酵母菌),分析其耐药性,并将其作为"干扰菌"与烟曲霉标准株的孢子以不同比例混合接种培养,模拟痰标本的混合感染,观察彼此的干扰情况。同时添加抗菌药物于MediumB培养基中,分析培养基对烟曲霉的生长选择性。结果:当铜绿假单胞菌浓度≥104CFU/mL时,即可完全抑制烟曲霉(103CFU/mL)的生长;金黄色葡萄球菌和大肠埃希菌则必须在>105 CFU/mL时,才能完全抑制103 CFU/mL的烟曲霉生长;当白假丝酵母菌与烟曲霉以100∶1混合接种时,其基本抑制了烟曲霉的生长。根据"干扰菌"的耐药特性,同时添加亚胺培南和万古霉素至培养基,结果显示其能有效抑制上述3种细菌的生长;添加氟康唑5μg/mL可抑制白假丝酵母菌的生长,而上述3种药物对烟曲霉的生长均无影响。结论:在所研究的真菌分离培养基中添加适宜的抗细菌及抗真菌药物,可有效抑制"干扰菌",提高烟曲霉的检出率。     

Influence of carbon dioxide on the MIC of telithromycin for Streptococcus pneumoniae: an in vitro-in vivo study

Incubation in CO(2) resulted in higher (> or =3 doubling dilution) MICs of telithromycin than those found in ambient air for 31.2% of 346 Streptococcus pneumoniae ermB-positive strains. An increased telithromycin MIC in CO(2) was not correlated with loss of its activity in the murine sepsis/peritonitis model.     

In vitro-in vivo correlation of hepatobiliary drug clearance in humans

The biliary clearance (Cl(biliary)) of three compounds was estimated using sandwich-cultured human hepatocytes (SCHH) and compared with Cl(biliary) values measured in vivo. Tc-99m sestamibi (MIBI) Cl(biliary) was determined in seven healthy volunteers using an oroenteric catheter to aspirate duodenal secretions, and gamma scintigraphy to determine gallbladder contraction; this technique was used previously to determine Tc-99m mebrofenin (MEB) and piperacillin (PIP) in vivo Cl(biliary). In vitro Cl(biliary) of MEB, MIBI, and PIP was quantified in SCHH as the ratio of mass excreted into bile canaliculi and area under the blood concentration-time curve (AUC) in medium. MIBI Cl(biliary) in vivo was 5.5+/-1.2 mL/min/kg (mean+/-SD). The rank order of Cl(biliary) predicted from SCHH corresponded well with the in vivo Cl(biliary) values in mL/min/kg for MEB (7.44 vs 16.1), MIBI (1.20 vs 5.51), and PIP (0.028 vs 0.032). In conclusion, the methods developed allowed for reproducible quantification of Cl(biliary) of drugs in healthy humans and prediction of Cl(biliary) from in vitro data.     

Fluvastatin potentiates the activity of caspofungin against Aspergillus fumigatus in vitro

Statins (anticholesterol drugs) inhibit HMG-CoA reductase, which is a key rate-limiting enzyme in the synthesis of sterols in fungi. We therefore investigated the in vitro inhibitory activity of various statins against Aspergillus fumigatus alone and in combination with antifungal drugs. Fresh conidial suspensions from 10 clinical isolates of A. fumigatus were obtained. The MIC and minimum fungicidal concentration (MFC) were determined by the Clinical and Laboratory Standards Institute M-38A protocol and the fungicidal activity by time–kill study. Fluvastatin (FST) showed good activity (MIC, 2 mg/L; MFC, 4 mg/L) against A. fumigatus; other statins had no activity (MIC ≥256 mg/L). FST enhanced the activity of caspofungin (CFG) against A. fumigatus; subinhibitory concentrations of FST in combination with CFG showed >99.9% killing of A. fumigatus conidia, whereas either drug alone showed poor activity at subinhibitory concentrations. FST potentiated the antifungal activity of CFG but displayed no specific interaction with voriconazole or amphotericin B.     

In vitro activities at pH 5.0 and pH 7.0 and in vivo efficacy of flucytosine against Aspergillus fumigatus

The antifungal agent flucytosine was found to be active in vitro against Aspergillus fumigatus isolates when the MIC was determined at pH 5.0 instead of pH 7.0. The in vitro MIC at pH 5.0 corresponded to the in vivo efficacy of flucytosine monotherapy in a murine model of invasive aspergillosis.     

烟曲霉菌对唑类抗真菌药的耐药机制研究进展

唑类抗真菌药是曲霉病处理中一种最为常用的药物,而曲霉病主要是由烟曲霉菌(Aspergillus fumigatus)感染引起的。越来越多的报道发现A.曲霉株(A.fumigatus isolates)具有唑类抗真菌药耐药性,这是曲霉病治疗中一个巨大的挑战。A.曲霉唑类抗真菌药耐药株(ARAF)在侵袭性曲霉病患者中具有非常高的致死率,这对临床微生物学者如何及时诊断耐药性和提出合适的干预策略等方面提出极大的挑战。ARAF耐药株既存在cyp51A突变型又存在cyp51A非突变型,而且cyp51A非突变型在唑类抗真菌药耐药中占有的比重越来越高,为临床的诊断和治疗提出了更高的挑战。本综述总结了目前A.曲霉唑类抗真菌药耐药株在全球各国的发病情况及其耐药机制研究的最新进展。