Interference of melanin in the susceptibility profile of Sporothrix species to amphotericin B

BackgroundThe presence of melanin in the fungal cell is a major virulence factor of the genus Sporothrix since it protects the fungal cells against the defense systems.AimsThe present study aimed to investigate the interference of melanin in the susceptibility of Sporothrix brasiliensis and Sporothrix schenckii sensu stricto to amphotericin B and itraconazole, drugs recommended as therapy for disseminated and subcutaneous sporotrichosis, respectively.MethodsYeast cells were cultivated in minimal medium with or without l-DOPA in order to induce the production of melanin. Microdilution and killing assay methods were used to determine the antifungal activity against yeast cells with different amounts of melanin.ResultsThe killing assay showed that melanization protected isolates within the S. schenckii complex from amphotericin B, particularly in the lower concentrations tested.ConclusionsStudies combining amphotericin B and inhibitors of melanin are required in order to avoid this effect.     

Complexes of Amphotericin B and Cholesteryl Sulfate

Abstract

To improve the clinical utility of amphotericin B, we have developed a novel formulation of amphotericin B, Amphocil® (also known as Amphotericin B Colloidal Dispersion, or ABCD). Amphocil is a uniform disc-shaped complex of amphotericin B and sodium cholesteryl sulfate in a molar ratio of 1:1. The complex has a mean hydrodynamic diameter of approximately 115 nm and is thermodynamically stable. In an extensive series of pharmacodynamic, pharmacokinetic and toxicology studies, Amphocil was found to be less toxic than conventional amphotericin B (Fungizone®), providing a four- to five-fold improvement in safety, while remaining effective in treating a variety of fungal infections. Plasma pharmacokinetics and tissue disposition of amphotericin B differ in several respects after administration of Amphocil and conventional amphotericin B, due to a rapid uptake of Amphocil by liver. Animals receiving Amphocil demonstrated reduced peak levels in plasma, prolonged residence time and lowered levels of amphotericin B in most tissues including the kidney, the major target organ for toxicity, compared with animals receiving conventional amphotericin B.

In healthy male subjects receiving a single dose of Amphocil, ranging from 0.25-1.5 mg/kg, mild to moderate dose-dependent acute side effects typically seen with conventional amphotericin B were observed but there was no sign of renal or hepatic toxicities. In two dose-escalating studies, multiple daily doses of Amphocil up to 4.5 mg/kg were well tolerated in patients who had previously failed to tolerate or respond to conventional amphotericin B. In addition, complete clearance of fungal infection was observed with the Amphocil therapy. Thus, Amphocil is a safe and effective agent for treating systemic mycoses. Toleration and efficacy of higher doses of Amphocil in patients with life-threatening mycoses is currently being evaluated.     

Aspergilosis pulmonar en un paciente crítico no inmunodeprimido

BackgroundIn non-immunocompromised patients admitted to intensive care departments or units (ICU), it is difficult to establish a definitive diagnosis of pulmonary aspergillosis because the signs and symptoms of this infectious disease are non-specific, and serological techniques are not very specific as well. For this reason, a diagnosis of possible pulmonary aspergillosis is initially established, and the starting of the treatment is controversial.Case reportAn immunocompetent subject had a work-related accident after a fall, which resulted in multiple injuries (head, thorax, lower extremities). The patient required mechanical ventilation since admission. On the second week of ICU admission, he showed a clinical presentation of respiratory infection with fever, purulent secretions, bilateral pulmonary infiltrates and repeated isolation of Mucor and Aspergillus fumigatus in bronchial secretions and pharyngeal swabs. The patient was treated with amphotericin B lipid complex and voriconazole with an excellent clinical and radiological outcome.ConclusionsCombined treatment of antifungal agents, in this case amphotericin B lipid complex and voriconazole, is a therapeutic possibility to be considered in patients who failed to respond to initial antifungal monotherapy.     

Arguments for a New Formulation of Liposomal Amphotericin B: An Historical Perspective

Abstract

Dr. Armstrong's expert knowledge and vast experience with amphotericin B have allowed him to speak previously with authority on its merits and demerits. According to his assessment, amphotericin B is a valuable drug, marred by severe toxicity. I shall attempt to explain, in this short presentation, why liposomes as vehicles in which to administer amphotericin B have the potential to redress this agent's principal deficiency.     

Unilamellar-Vesicle Systems as Model for Studying Membrane Permeabilization by Polyene Antibiotics

Abstract

Permeabilization of phospholipid/sterol unilamellar vesicles by polyene antibiotics (amphotericin B and lucensomycin) was studied by measuring proton leakage with a pH-stat method. The percentage of proton release was directly related to the antibiotic concentration. Using ergosterol-containing vesicles, a relevant proton efflux was induced by micromolar concentrations of amphotericin B, whereas lucensomycin caused membrane permeabilization at higher concentrations (0.1 mM). Cholesterol-containing vesicles were less sensible to the lytic action of polyenes. When amphotericin B was carried in cholesterol-containing liposomes, the selectivity towards ergosterol-containing vesicles was enhanced. An increase in drug selectivity was also observed by dissolving amphotericin B in fresh human plasma. At concentrations one order of magnitude lower than those necessary to induce a detectable proton efflux, lucensomycin seemed to protect the vesicles from the subsequent permeabilizing action of amphotericin B.     

两性霉素B联合氟康唑治疗艾滋病合并新型隐球菌性脑膜脑炎的疗效预测因素分析

目的:探讨两性霉素B联合氟康唑治疗艾滋病合并新型隐球菌性脑膜脑炎(简称"艾滋病合并隐脑")的疗效预测因素。方法:回顾性收集2010年1月1日-2016年12月31日58例在首都医科大学附属北京佑安医院住院治疗且接受两性霉素B联合氟康唑治疗的艾滋病合并隐脑患者的临床资料,分析其疗效预测因素及预测价值。结果:根据预后将患者分为好转组(38例)和死亡组(20例),单因素分析结果显示两组之间CD4+T细胞计数、脑脊液细胞计数比较有统计学差异(P分别为0.032,0.001)。Logistic回归多因素分析结果显示脑脊液细胞计数是两性霉素B联合氟康唑治疗艾滋病合并隐脑的疗效预测因素(P=0.023),Exp(B)=1.01,95%置信区间为1.00-1.03。ROC曲线对脑脊液细胞计数的预测价值进行分析,结果显示曲线下面积为0.889,预测阈值为261个/mm3,对应的敏感性=0.684,特异性=1.0。结论:脑脊液细胞计数是两性霉素B联合氟康唑治疗艾滋病合并新型隐球菌性脑膜脑炎良好的疗效预测参考因素。     

Homology Modeling and Docking Studies of Human Bcl-2L10 Protein

Abstract

Bradykinin is a bioactive hormone involved in a variety of physiological processes. In various solvents, this peptide adopts β-turn structures. The C-terminal turn is a structural feature for the receptor affinity of agonists and antagonists while the N-terminal turn might be important for antagonistic activities. Polyphenols like dimeric proanthocyanidin B3 interact with the peptide. Thus to investigate the effects of polyphenols on bradykinin activity and structure, we studied the interaction in the structuring solvent DMSO which can be a close mimic of aqueous physiological environments like receptor-binding sites. Bradykinin alone presented a folded structure with two turns. B3 interacted with the peptide C-terminus and involved the loss of the bend structure of this region, while the N-ter-minus turn was maintained. Numerous studies have shown that polyphenolic molecules can act upon various biological targets, and the formation of this type of complex might be one of the possible modes of action.     

Antifungal Activity of Antifungal Drugs,as Well as Drug Combinations Against <Emphasis Type="Italic">Exophiala dermatitidis</Emphasis>

To evaluate the in vitro efficacy of common antifungal drugs, as well as the interactions of caspofungin with voriconazole, amphotericin B, or itraconazole against the pathogenic black yeast Exophiala dermatitidis from China, the minimal inhibitory concentrations (MICs) of terbinafine, voriconazole, itraconazole, amphotericin B, fluconazole, and caspofungin against 16 strains of E. dermatitidis were determined by using CLSI broth microdilution method (M38-A2). The minimal fungicidal concentrations (MFCs) were also determined. Additionally, the interactions of caspofungin with voriconazole, amphotericin B, itraconazole or fluconazole, that of terbinafine with itraconazole, or that of fluconazole with amphotericin B were assessed by using the checkerboard technique. The fractional inhibitory concentration index (FICI) was used to categorize drug interactions as following, synergy, FICI ≤ 0.5; indifference, FICI > 0.5 and ≤4.0; or antagonism, FICI > 4.0. The MIC ranges of terbinafine, voriconazole, itraconazole, amphotericin B, fluconazole, and caspofungin against E. dermatitidis were 0.06–0.125 mg/l, 0.25–1.0 mg/l, 1.0–2.0 mg/l, 1.0–2.0 mg/l, 16–64 mg/l, and 32–64 mg/l, respectively. The in vitro interactions of caspofungin with voriconazole, amphotericin B, and itraconazole showed synergic effect against 10/16(62.5%), 15/16(93.75%), and 16/16(100%) isolates, while that of caspofungin with fluconazole showed indifference. Besides, the interaction of terbinafine with itraconazole as well as that of fluconazole with amphotericin B showed indifference. Terbinafine, voriconazole, itraconazole, and amphotericin B have good activity against E. dermatitidis. The combinations of caspofungin with voriconazole, amphotericin B or itraconazole present synergic activity against E. dermatitidis. These results provide the basis for novel options in treating various E. dermatitidis infections.     

Sensibilidad de aislamientos de Candida albicans de hemocultivos a 3 fármacos: estudio retrospectivo en Rio Grande do Sul,Brasil, 1999 a 2009

BackgroundCandidiasis is one of the most important among recurrent invasive yeast infections in patients, thus antifungal treatment becomes a challenge.AimsThe aim of this study was to evaluate the in vitro activity of clinical Candida albicans isolates from blood cultures to fluconazole, amphotericin B and anidulafungin, in a hospital from Rio Grande do Sul, Brazil.MethodsThe susceptibility of 153 isolates to the 3 drugs mentioned was tested according to Clinical and Laboratory Standars Institute. Minimal inhibitory and fungicidal concentrations (MIC, MFC, respectively) of each drug were determined, as well as the epidemiological cutoff value (ECV).ResultsAll of the isolates were susceptible to anidulafungin, MIC and MFC ≤ 1 μg/ml; however, when compared with ECV, 3% of the isolates exhibited higher values against fluconazole, 96% were susceptible, 3% susceptible dose-dependent, and 1% resistant. Also, it was observed that 21% of the isolates exhibited higher values than ECV. One isolate was resistant to amphotericin B; the other ones, susceptible, based on the MFC; furthermore, 1.5% of the isolates exhibited higher values.ConclusionsC. albicans isolates exhibited more susceptibility to anidulafungin, and 90% of them (MIC₉₀) exhibited the lowest values against amphotericin B. Based on ECV and Pfaller classification, isolates could be resistant to fluconazole, demonstrating the importance of the combination of these parameters.     

Development,Characterization, Efficacy and Mode of Action of Ambisome,A Unilamellar Liposomal Formulation of Amphotericin B

Abstract

AmBisome is a lyophilized formulation of amphotericin B incorporated into small unilamellar liposomes composed of hydrogenated soy phosphatidylcholine, distearoyl phosphatidylglycerol, and cholesterol. In aqueous solution AmBisome is quite stable; less than 5% of the drug dissociates from the liposomes during a 72 hour incubation period in human plasma. This stability to loss of drug is a key factor, accounting for the ability of AmBisome to markedly reduce the well known acute and chronic toxicities associated with administration of amphotericin B. Numerous animal and clinical studies have documented therapeutic efficacy of AmBisome for a wide range of fungal infections. Mechanism of action studies indicate that AmBisome liposomes specifically bind to the fungal cell surface, dam the cell membrane, and kill the fungus. In some cases, AmBisome had a slightly lower potency than amphotericin B itself, but much higher doses of AmBisome could be administered safely resulting in an improved therapeutic profile.     

Epidemiología de las fungemias en un hospital pediátrico de alta complejidad

BackgroundA retrospective study on the epidemiology of fungaemia due to yeasts of medical importance at the Hospital Nacional de Pediatría Prof. Dr. J. Garrahan, Buenos Aires was conducted between September 2001 and September 2003.ObjectivesTo learn the distribution of yeast species and to evaluate their in vitro antifungal susceptibility profile.MethodsThe minimum inhibitory concentration (MIC) was determined according to the CLSI M27-A2 procedure, and time kill curves against amphotericin B were also performed.Results-ConclusionsThe species isolated were Candida parapsilosis (32.6% of isolates); Candida albicans (26.5%), Candida tropicalis (24.5%), and other yeasts (16.4%). Candida isolates were susceptible to the antifungals evaluated, but amphotericin B-tolerant isolates were detected using time kill curves.     

Successful posaconazole salvage therapy for rhinocerebral mucormycosis in a child with leukemia. Review of the literature

BackgroundMucormycosis is a fungal infection caused by species of the Mucorales order. These microorganisms are angioinvasive, with rapid disease progression and potentially lethal in its rhinocerebral form.Case reportWe present the case of a 12-year-old female with trisomy 21, acute lymphoblastic leukemia and diabetes, with fever and neutropenia who developed rhinocerebral mucormicosis. After treatment with amphotericin B lipid complex and extensive surgery, disease progressed and posaconazole was added as salvage treatment with full remission of the infection. Four years after diagnosis the patient continues without relapse of mucormycosis or leukemia.ConclusionsThis case highlights the use of posaconazole as either monotherapy or combined therapy. Although it is still debated, it can be considered an option for salvage treatment in children with non-responding mucormycosis, despite lack of standard dosage in pediatric patients.     

Leishmania-HIV Co-infection: Clinical Presentation and Outcomes in an Urban Area in Brazil

BackgroundVisceral leishmaniasis (VL) is an emerging condition affecting HIV-infected patients living in Latin America, particularly in Brazil. Leishmania-HIV coinfection represents a challenging diagnosis because the clinical picture of VL is similar to that of other disseminated opportunistic diseases. Additionally, coinfection is related to treatment failure, relapse and high mortality.ObjectiveTo assess the clinical-laboratory profile and outcomes of VL-HIV-coinfected patients using a group of non HIV-infected patients diagnosed with VL during the same period as a comparator.MethodsThe study was conducted at a reference center for infectious diseases in Brazil. All patients with suspected VL were evaluated in an ongoing cohort study. Confirmed cases were divided into two groups: with and without HIV coinfection. Patients were treated according to the current guidelines of the Ministry of Health of Brazil, which considers antimony as the first-choice therapy for non HIV-infected patients and recommends amphotericin B for HIV-infected patients. After treatment, all patients with CD4 counts below 350 cells/mm³ received secondary prophylaxis with amphotericin B.ResultsBetween 2011 and 2013, 168 patients with suspected VL were evaluated, of whom 90 were confirmed to have VL. In total, 51% were HIV coinfected patients (46 patients). HIV-infected patients had a lower rate of fever and splenomegaly compared with immunocompetent patients. The VL relapse rate in 6 months was 37% among HIV-infected patients, despite receiving secondary prophylaxis. The overall case-fatality rate was 6.6% (4 deaths in the HIV-infected group versus 2 deaths in the non HIV-infected group). The main risk factors for a poor outcome at 6 months after the end of treatment were HIV infection, bleeding and a previous VL episode.ConclusionAlthough VL mortality rates among HIV-infected individuals are close to those observed among immunocompetent patients treated with amphotericin B, HIV coinfection is related to a low clinical response and high relapse rates within 6 months.     

Comparison of Commercial Methods and the CLSI Broth Microdilution to Determine the Antifungal Susceptibility of Candida parapsilosis Complex Bloodstream Isolates from Three Health Institutions in Rio de Janeiro,Brazil

Two commercial methods, the Etest and Vitek 2, were compared with the Clinical and Laboratory Standards Institute broth microdilution method to determine the susceptibility of Candida parapsilosis complex to amphotericin B, caspofungin, fluconazole, voriconazole, and itraconazole. One-hundred bloodstream isolates of C. parapsilosis complex from three hospitals in Rio de Janeiro city, Brazil, between 1998 and 2006 were analyzed. C. parapsilosis sensu stricto (61 %) was the predominant species, followed by C. orthopsilosis (37 %) and C. metapsilosis (2 %). Most isolates were susceptible to the tested drugs. However, one C. parapsilosis sensu stricto isolate was considered resistant for amphotericin B. The essential agreement was 100 % between the methods, except for itraconazole (96.3 %). The categorical agreement varied for fluconazole and itraconazole by Etest and for amphotericin B and fluconazole by Vitek 2. This study reinforces the suitability of the commercial methods in routine clinical microbiology laboratories for antifungal susceptibility testing.     

Nosocomial Invasive Infection Caused by Cunninghamella bertholletiae: Case Report

Human infection by Cunninghamella bertholletiae occurs almost exclusively in immunocompromised patients. Infections due to this microorganism have been most frequently diagnosed in patients with hematological malignancies, with neutropenia and in diabetes mellitus patients. This work reports a case of fungal infection by Cunninghamella bertholletiae isolated from blood in a man with a complex clinical picture, involving diabetes and pharmacological immunosupression. Blood culture at room temperature and at 37 °C on Sabouraud agar grew a single mold with characteristic properties of Cunninghamella. In the microscopic morphology, were found wide, non-septate, branching hyphae with erect sporangiophores terminated in swollen vesicles and sporangioles borne off the vesicles. C. bertholetiae was identified after subculture on Sabouraud dextrose agar at 45 °C. The patient died 15 days after the beginning of amphotericin B therapy.     

Crystal and Solution Structure of the Bi-Loop Motif in Cyclic Octanucleotides

Abstract

The refined NMR structures of the cyclic octamers d?pATTCATTC?1 and d?pGCTCGCTT?2 are consistent with the reported Crystallographic data of 1 and the linear heptamer d(GCATGCT), respectively. The NMR study of four new cyclic octamers shows that in all cases a dimeric bi-loop structure is observed in equilibrium with a monomeric form.     

儿童重症监护病房医院感染暴发白色念珠菌血流感染4例分析

摘要 目的：探讨儿童重症监护病房白色念珠菌血流感染暴发的临床表现、危险因素、控制措施等,为预防和控制院内白色念珠菌血流感染暴发提供科学依据。方法：以2018年7月我院儿童重症监护病房发生的4例白色念珠菌血流感染暴发患儿为研究对象,分析患儿临床情况、临床特征、危险因素、暴发原因以及采取的预防控制措施。结果：4例医院感染暴发白色念珠菌血流感染患儿均存在基础疾病、有机械通气史、存在中心静脉或动脉置管、静脉或动脉置管前后均使用碘伏消毒、曾使用广谱抗生素、输血制品,白色念珠菌血流感染后最突出的临床表现均是发热。药敏方面,医院感染暴发的4例白色念珠菌感染患儿对唑类及5-氟胞嘧啶均耐药,但对两性霉素B均敏感。经拔除血管置管、减少或者避免广谱抗菌药的应用,根据药敏使用卡泊芬净及两性霉素B抗真菌等积极治疗,1例患儿放弃治疗后死亡,3例患儿顺利出院。通过Fisher确切概率法分析可知,留置中心静脉或动脉置管是儿童重症监护病房发生医院感染暴发白色念珠菌血流感染的危险因素（P<0.05）。结论：留置中心静脉或动脉置管是儿童重症监护病房发生医院感染暴发白色念珠菌血流感染的危险因素,医院感染暴发白色念珠菌血流感染患儿最突出的临床表现是发热,唑类及5-氟胞嘧啶耐药的患儿使用卡泊芬净及两性霉素B可能获得较好的治疗效果。     

Renal abscess due to Aspergillus fumigatus as the only sign of disseminated aspergillosis in a patient with AIDS

BackgroundAspergillus fumigatus can cause a wide variety of clinical syndromes, especially in the three largest immunocompromised groups, such as HIV-infected patients. Primary renal aspergillosis is an extremely rare entity.AimsWe report an unusual case of renal abscess due to Aspergillus fumigatus in a patient with AIDS.MethodsWe review clinical and laboratory records, and provide follow up of the patient.ResultsA 38-year-old man, HIV seropositive, was admitted to our hospital with fever, lumbar pain and respiratory symptoms. Abdominal ultrasound and computerised tomography showed a single and large lesion consistent with an abscess located in the left kidney. Aspergillus fumigatus was isolated from clinical sample obtained by ultrasound-guided needle aspiration. Despite a correct treatment based on amphotericin B and drainage of the abscess, surgery was necessary and nephrectomy was carried out. Histopathological examination of the surgical specimen confirmed the diagnosis of renal aspergillosis. Systemic antifungal therapy based on intravenous and oral voriconazole and highly active antiretroviral therapy was started after surgery. The patient had a good response to the established treatment and he remains in a good clinical condition at one year of follow up.ConclusionsCombined medical and surgical treatment is the elective therapy for renal abscesses due to Aspergillus when percutaneous drainage and the administration of systemic antifungal drugs, such as amphotericin B and/or oral voriconazole or itraconazole, fail. This case emphasizes renal fungal infections should be included in the differential diagnosis of kidney abscesses in AIDS patients.     

Amphotericin B inhibits entry of Leishmania donovani into primary macrophages

Visceral leishmaniasis is a vector-borne disease caused by an obligate intra-macrophage protozoan parasite Leishmania donovani. The molecular mechanisms involved in internalization of Leishmania are still poorly understood. Amphotericin B and its formulations are considered as the best existing drugs against visceral leishmaniasis and are being increasingly used. The reason for its antileishmanial activity is believed to be its ability to bind ergosterol found in parasite membranes. In case of in vivo amphotericin B treatment, both host macrophages and parasites are exposed to amphotericin B. The effect of amphotericin B treatment could therefore be due to a combination of its interaction with both sterols i.e., ergosterol of Leishmania and cholesterol of host macrophages. We report here that cholesterol complexation by amphotericin B markedly inhibits binding of L. donovani promastigotes to macrophages. These results represent one of the first reports on the effect of amphotericin B on the binding of Leishmania parasites to host macrophages. Importantly, these results offer the possibility of reevaluating the mechanism behind the effectiveness of current therapeutic strategies that employ sterol-complexing agents such as amphotericin B to treat leishmaniasis.