Determination of susceptibility/resistance to antifungal drugs of Trichophyton mentagrophytes isolates by a macrodilution method

Onychomycosis is a common adult human mycosis, and dermatophytes of the Trichophyton genera are the most frequently isolated microorganism. Globally, from 3% to 10% of the human population is attacked by ony cho mycosis, and many cases involve toenails. The aim of this work was to determine the minimal inhibitory concentrations (MICs) of antifungal drugs (fluconazole, ketoconazole, itraconazole, terbinafine, and griseofulvin) often used for the treatment of ungueal dermatophytosis caused by Trichophyton mentagrophytes. The MICs were determined by the broth medium macrodilution method. The results showed that activities of terbinafine and itraconazole were significantly higher (MIC <0.007-0.015 microg.mL -1 and MIC = 0.062-1.000 microg.mL -1, respectively). All isolates had reduced susceptibility to fluconazole (MIC = 16 to >64 microg.mL -1). The MICs of ketoconazole and griseofulvin varied among strains, ranging from 0.125 to 2.000 microg.mL -1 for ketoconazole and from 0.25 to 2.00 microg.mL -1 for griseofulvin. These MICs were higher than those of other studies cited, possibly because of differences in culture medium used in the other studies.     

In vitro activities of voriconazole, fluconazole, itraconazole and amphotericin B against non Candida albicans yeast isolates

Antifungal susceptibility testing was performed on 197 yeast isolates from the BCCM/IHEM biomedical fungi and yeasts collection (Belgian Co-ordinated Collections of Micro-organisms / IPH-Mycology) to study the in vitro activity of voriconazole against fluconazole, itraconazole and amphotericin B. MICs of the four antifungal agents were determined by an adapted NCCLS M27-A microdilution reference method. MIC readings were visually and spectrophotometrically determined. Optical density data were used for calculation of the MIC endpoints. For amphotericin B, the MIC endpoint was defined as the minimal antifungal concentration that exerts 90% inhibition, compared to the control growth. The azoles endpoints were determined at 50% inhibition of growth. The MIC distribution of voriconazole susceptibilities showed that 193 isolates had a MIC < or = 2 microg/ml and 185 a MIC < or = 1 microg/ml. Cross-tabulation of voriconazole, fluconazole, and itraconazole MICs indicated that voriconazole MICs raised with fluconazole and itraconazole MICs. The in vitro data obtained in this study suggest that voriconazole may also be effective treating yeast infection in patients infected with fluconazole or itraconazole resistant isolates.     

Etest for assessing the susceptibility of filamentous fungi

The purpose of this study was to evaluate the Etest as an in vitro antifungal susceptibility test method for different moulds originating from human samples and from the environment. A total of 50 isolates (1 Acremonium, 18 Aspergillus, 2 Cladosporium, 1 Epicoccum, 15 Penicillium, 2 Scopulariopsis and 11 Trichoderma strains) were tested by the Etest. Forty-six of the tested moulds (92%) were resistant to fluconazole with minimal inhibitory concentrations (MICs) > or = 256 microg ml(-1). There were strains resistant to ketoconazole among Aspergillus niger, A. ochraceus and Cladosporium spp. with MICs > 32 microg ml(-1). For fluconazole, no differences were observed using two different inocula, while for itraconazole, ketoconazole and amphotericin B, a 1 or less step 2-fold dilution difference in MIC was seen for the most of 10 selected strains. The MICs of fluconazole and amphotericin B obtained for Trichoderma strains by the Etest and the agar dilution method were also compared. MICs for fluconazole were in agreement, while MICs for amphotericin B were higher with 1 or 2 steps of 2-fold dilutions for most of Trichoderma strains in the case of the agar dilution method.     

Subculture on potato dextrose agar as a complement to the broth microdilution assay for Malassezia pachydermatis

The main aim of this study was to verify the efficacy of subculture on potato dextrose agar (PDA) as a complement to the in vitro susceptibility test for Malassezia pachydermatis strains by a broth microdilution method, as well as to determine the MIC and MFC of azole derivatives, amphotericin B and caspofungin. The microdilution assay was performed in 96-well plates using a modified RPMI 1640 medium. The M. pachydermatis strains were resistant to caspofungin. All strains (n=50) had shown MIC values of <0.03, <0.03, 2.0, 4.0 and 4.0 mug/ml for itraconazole, ketoconazole, voriconazole, fluconazole and amphotericin B, respectively. Thus, the subculture on PDA improved the analysis of the in vitro antifungal susceptibility of M. pachydermatis.     

Carboxylic acid and phosphate ester derivatives of fluconazole: synthesis and antifungal activities

Two classes of fluconazole derivatives, (a) carboxylic acid esters and (b) fatty alcohol and carbohydrate phosphate esters, were synthesized and evaluated in vitro against Cryptococcus neoformans, Candida albicans, and Aspergillus niger. All carboxylic acid ester derivatives of fluconazole (1a-l), such as O-2-bromooctanoylfluconazole (1g, MIC=111 microg/mL) and O-11-bromoundecanoylfluconazole (1j, MIC=198 microg/mL), exhibited higher antifungal activity than fluconazole (MIC > or = 4444 microg/mL) against C. albicans ATCC 14053 in SDB medium. Several fatty alcohol phosphate triester derivatives of fluconazole, such as 2a, 2b, 2f, 2g, and 2h, exhibited enhanced antifungal activities against C. albicans and/or A. niger compared to fluconazole in SDB medium. For example, 2-cyanoethyl-omega-undecylenyl fluconazole phosphate (2b) with MIC value of 122 microg/mL had at least 36 times greater antifungal activity than fluconazole against C. albicans in SDB medium. Methyl-undecanyl fluconazole phosphate (2f) with a MIC value of 190 microg/mL was at least 3-fold more potent than fluconazole against A. niger ATCC 16404. All compounds had higher estimated lipophilicity and dermal permeability than those for fluconazole. These results demonstrate the potential of these antifungal agents for further development as sustained-release topical antifungal chemotherapeutic agents.     

Molecular typing and antifungal susceptibility of clinical sequential isolates of Cryptococcus neoformans from Sao Paulo State, Brazil

The antifungal susceptibility profiles and the genetic variability of 83 sequential clinical isolates of Cryptococcus neoformans, including four Cryptococcus gattii isolates, obtained from 38 Sao Paulo AIDS patients with cryptococcal meningitis were assessed by electrophoretic karyotyping and random amplified polymorphic DNA (RAPD) analysis. The majority of the Cryptococcus neoformans isolates were highly susceptible to amphotericin B and fluconazole. Twenty percent of the minimum inhibitory concentration values for amphotericin B varied from 0.5 to 1 micro g mL(-1). For fluconazole, 22% occurred in the range 8-16 mug mL(-1). Sequential isolates from nine patients showed a trend towards lower susceptibility to fluconazole, flucytosine, itraconazole and amphotericin B. The results of molecular typing by electrophoretic karyotyping and RAPD analysis showed the presence of 22 electrophoretic karyotypes (EK) and 15 RAPD profiles that were highly correlated. Our results provided evidence for the occurrence of genetic changes in some strains associated with microevolution during the course of infection. We also observed both microevolution and simultaneous coinfection with two distinct Cryptococcus neoformans strains in one patient. In some patients, we found changed EK- and RAPD patterns in association with increased MIC values.     

Minimal inhibitory concentrations of Candida species to five antifungals by using the reference dilution micromethod and the E-test.

It is accepted that the frequency of candidosis has increased during the last decade, specially in hospitalized patients. The more frequent use of azole antifungals and the recognition of isolates of Candida sp resistant to these and other drugs such as 5-fluorocytosine constitute a great need for a reproducible and useful C. albicans in vitro susceptibility testing method for monitoring antifungal therapy in clinical mycological laboratories. The E-test is a novel agar diffussion technique for testing the susceptibility of yeasts against a defined continous gradient of drug and could be used by most clinical laboratories. In this study the E-test and the NCCLS reference microbroth method (M27-P guidelines) were used to determine the MICs of amphotericin B, 5-flucytosine, itraconazole, fluconazole and ketoconazole for 50 clinical isolates of Candida albicans, Torulopsis glabrata, C. tropicalis and Hansenula anomala and five reference ATCC strains. The main purpose of the study was to compare the results obtained by the two methods. In general good agreement (+/- 1 dilution) was otained between both methods, despite differences observed for some species-antifungal combinations in which the MICs were lower by the E-test than by the microbroth method. MICs for C. albicans and T. glabrata to amphotericin B were < 0.50 microg/mL. Two isolates of C. albicans and two others of H. anomala, showed MIC < 8 microg/mL for 5- flucytosine. All isolates of T. glabrata and 40% of C. albicans showed MICs > 16 microg/mL for fluconazole. The results of this study indicate that E-test is an alternative for susceptibility testing to the NCCLS reference method. Because its simplicity it seems to be an easier test for routine clinical laboratories.     

地塞米松影响念珠菌对抗真菌药物敏感性的实验研究

目的 探讨地塞米松在体外试验中是否影响念珠菌对抗真菌药物的敏感性,以了解糖皮质激素与抗真菌药物直接作用于念珠菌时是否存在相互作用。方法 用微量液体培养基稀释法分别测定26株白念珠菌与地塞米松（0．2mg／ml）共同孵育前、孵育24～48h及7d时氟康唑、伊曲康唑、两性霉素B的最低抑菌浓度（MIC）值,并作对照。结果 白念珠菌与地塞米松孵育24～48h后、孵育后第7d氟康唑和伊曲康唑的MIC值升高,分别与孵育前的MIC值存在统计学差异,但孵育24～48h后的MIC与孵育后第7d的MIC无统计学差异;白念珠菌与地塞米松共同孵育24～48h后两性霉素B的MIC值也较孵育前升高,但第7d的MIC值与孵育前无差异。结论 地塞米松可增加三种抗真菌药物对于白念珠菌的MIC,但三种抗真菌药物间存在差异,表明地塞米松对于氟康唑和伊曲康唑体外抗白念珠菌的活性有拮抗作用,但没有时间依赖性,地塞米松对于两性霉素B的影响较氟康唑和伊曲康唑小,且影响时间较短。     

Antifungal susceptibility of epigallocatechin 3-O-gallate (EGCg) on clinical isolates of pathogenic yeasts

This is the first report to investigate the antifungal susceptibility of 21 clinical isolates of seven Candida species to epigallocatechin 3-O-gallate (EGCg) and to compare with six antifungal agents, amphotericin B (AMPH), fluconazole (FLCZ), flucytosin (5FC), itraconazole (ITCZ), micafungin (MCFG), and miconazole (MCZ), using a method following the National Committee for Clinical Laboratory Standards (NCCLS) M27-A guidelines. Among the tested species, Candida glabrata exhibited the highest susceptibility to EGCg (MIC50, 0.5-1 microg/ml and MIC90, 1-2 microg/ml) compared favorably with FLCZ, although they were slightly less susceptible than to AMPH, 5FC, MCFG, ITCZ, and MCZ. Candida guilliemondii and Candida parapsilosis (MIC50, 1-4 microg/ml and MIC90, 2-16 microg/ml) were also susceptible to EGCg, although they appear to be slightly less susceptible to EGCg than C. glabrata and the other antifungal agents tested. Moreover, the susceptibility of Candida krusei strains (MIC50, 2 microg/ml and MIC90, 4-8 microg/ml) to EGCg was approximately 2- to 8-fold higher than those of 5FC and FLCZ. Our data indicate that EGCg can inhibit clinically pathogenic Candida species, although the concentrations of EGCg for antifungal susceptibility were slightly higher than those of tested antifungal agents on the whole. Based on these results, we suggest that EGCg may be effectively used as a possible agent or adjuvant for antifungal therapy in Candidiasis.     

Comparsion ofin vitro activities of antifungal drugs and propolis against yeasts isolated from patients with superficial mycoses

Thein vitro susceptibilities of propolis and antifungal drugs were determined against some yeasts isolated from patients with superficial mycoses. The agents tested included fluconazole, itraconazole, ketoconazole, terbinafine and propolis. MICs were determined by the broth microdilution technique following National Committee for Clinical Laboratory Standards document M27-P. For allCandida albicans isolates from the patients with superficial mycoses, ketoconazole presented higher (P<0.05) efficiency than that of the other antifungal agents tested. The geometric mean MIC values of antifungal drugs and propolis against the yeasts tested ranged from 0.087 to 12.69 μg/mL and 0.4–0.6 μg/mL, respectively. Propolis also showed an important antifungal activity against the yeasts tested, MIC ranges of the propolis were between 0.01–1.65 μg/mL. Based on these results, propolis requires further investigation as a potential agent for the treatment of superficial mycoses.     

Optically active antifungal azoles: synthesis and antifungal activity of (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazol-2-yl/1-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol

A series of (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazol-2-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol (11a-n) and (2R,3S)-2-(2,4-difluorophenyl)-3-(5-[2-[4-aryl-piperazin-1-yl]-ethyl]-tetrazole-1-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol (12a-n) has been synthesized. The antifungal activity of compounds was evaluated by in vitro agar diffusion and broth dilution assay. Compounds 11d and its positional isomer 12d having 3-trifluoromethyl substitution on the phenyl ring of piperazine demonstrated significant antifungal activity against variety of fungal cultures (Candida spp. C. neoformans and Aspergillus spp.). The compound 12d showed MIC value of 0.12 microg/mL for C. albicans, C. albicans V-01-191A-261 (resistant strain); 0.25 microg/mL for C. tropicalis, C. parapsilosis ATCC 22019 and C. krusei and MIC value of 0.5 microg/mL for C. glabrata, C. krusei ATCC 6258, which is comparable to itraconazole and better than fluconazole. Further, compound 11d showed significant activity (MIC; 0.25-0.5 microg/mL) against Candida spp. and strong anticryptococcal activity (MIC; 0.25 microg/mL) against C. neoformans.     

Evaluation of the Origin of a Sample of <Emphasis Type="Italic">Sporothrix Schenckii</Emphasis> that Caused Contamination of a Researcher in Southern Brazil

We report a case of a researcher from a laboratory of Mycology in Rio Grande do Sul, Brazil that presented a clinical evidence of sporotrichosis. The researcher had an accident while manipulating the microculture slides of chromoblastomycosis agents and presented a clinical evidence of sporotrichosis. As the laboratory has some cultures of Sporothrix schenckii, it was suggested that it might be a laboratory contamination. In order to test this hypothesis, the genotypic characterization of the samples was performed by means of the random amplified polymorphic DNA (RAPD) analysis method. In addition, we evaluated the in vitro antifungal activity of four antifungal agents against the isolated fungus. The sample obtained from the researcher was not genetically similar to any of the samples kept in the laboratory and showed the minimum inhibitory concentrations of 0.5 μg/mL for itraconazole and ketoconazole, >64 μg/mL for fluconazole and 0.125 μg/mL for terbinafine. It is suggested that the contamination had an environmental origin.     

In vitro resistance to fluconazole and itraconazole in clinical isolates of Candida spp and Cryptococcus neoformans

An in vitro susceptibility testing of 181 strains of six species of Candida and 21 strains of Cryptococcus neoformans was carried out in order to investigate the resistance to new antifungal drugs. We have studied clinical isolates from 200 different patients of Hospital del Mar (Barcelona) and Hospital La Inmaculada (Almería). An agar diffusion method (NeoSensitabs, Rosco, Taastrup, Denmark), was employed with fluconazole, itraconazole, and reference drugs amphotericin B, flucytosine, tioconazole and ketoconazole. A high level of susceptibility was found for amphotericin B in C. neoformans strains while 19% of them were resistant to flucytosine. All the strains of C. neoformans and Candida guilliermondii were susceptible to the new azoles derivatives and also Candida parapsilosis and Candida albicans had a great susceptibility to this antifungals. A greater level of resistance was found for Candida krusei, Candida tropicalis and Candida glabrata to fluconazole, itraconazole and ketoconazole, but resistance to fluconazole and itraconazole is not always linked because ten resistant strains for fluconazole were susceptible to itraconazole, and two other resistant to itraconazole were susceptible to fluconazole.     

Oxovanadium(IV) complexes of hydrazides: potential antifungal agents

Oxovanadium(IV) -derived antifungals have been prepared by condensing equimolar amounts of vanadyl sulfate with hydrazides. All the synthesized ligands and their metal complexes were characterized by IR, UV-Visible and micro analytical data. These synthesized compounds were screened for their antifungal activity against Aspergillus flavus (A. flavus), Trichophyton longifusus (T. longifusus), Candida albicans (C. albicans), Microsporum canis (M. canis), Fusarium solani (F. solani) and Candida glaberata (C. glaberata) fungal strains. All complexes showed promising antifungal activity against different fungal strains with the exception of F. Solani and C. glaberata. Minimum Inhibitory Concentration (MIC) of different complexes and ligands are in the range of 250 to 400 microg/mL. Complex 7a and ligand 13 exhibit lowest MIC of 250 microg/mL whereas, complex 5a and ligands 2, 7 and 14 showed highest MIC of 400 microg/mL.     

Microbiological Characteristics and Susceptibility Patterns of Strains of Rhodotorula Isolated from Clinical Samples

The members of the genus Rhodotorula show a marked ubiquity. In man, they have been isolated from faeces, nails, skin, sputum, digestive tract and adenoids, forming part of the normal human flora, although in recent years cases have been reported of both local and systemic infection by this yeast. There are virtually no studies in the literature on the sensitivity of this genus to the antifungal agents in common clinical use. Therefore, it is considered of interest to study the microbiological characteristics and the susceptibility patterns of Rhodotorula isolated from clinical samples. A total of 35 different strains of Rhodotorula were studied. In vitro susceptibility testing to 5-fluorocytosine, amphotericin B, ketoconazole, fluconazole and itraconazole was performed. All the strains were considered sensitive to 5-fluorocytosine, amphotericin B, ketoconazole and itraconazole and resistant to fluconazole. As a conclusion, we can state that all the antifungal agents tested, except fluconazole, are useful medicaments for the treatment of infections by the Rhodotorula genus. This revised version was published online in June 2006 with corrections to the Cover Date.     

Antifungal susceptibility profiles of <Emphasis Type="Italic">Coccidioides immitis</Emphasis> and <Emphasis Type="Italic">Coccidioides posadasii</Emphasis> from endemic and non-endemic areas

Coccidioidomycosis is a systemic fungal infection endemic in Southwestern United States, Mexico, Central and South America. The causal agents are Coccidioides immitis and C. posadasii. A large number of cases of coccidioidomycosis in New York State residents were identified. We compared susceptibility profiles of these isolates and of C. immitis isolates from California using mycelial phase inoculum and CLSI (NCCLS) M38–A broth microdilution protocol. Minimum fungicidal concentrations (MFC) were also determined. Results indicated that geometric mean MICs of amphotericin B (AMB, 0.06 μg/ml), fluconazole (FLC, 8.0 μg/ml), itraconazole (ITC, 0.07 μg/ml), ketoconazole (KTC, 0.04 μg/ml), voriconazole (VRC, 0.04 μg/ml), posaconazole (PSC, 0.17 μg/ml) and caspofungin (CSP, 0.15 μg/ml) were in susceptible range as per breakpoints published for pathogenic Candida species. However, geometric MFC for FLC was relatively higher (52.4 μg/ml). Also, no significant difference in MIC and MFC values was evident for C. immitis and C. posadasii isolates. In conclusion, current methods for antifungal susceptibility testing yield reproducible profiles for Coccidioides species, which appear to be highly susceptible to most antifungal agents.     

Carbon analogs of antifungal dioxane-triazole derivatives: synthesis and in vitro activities

A new series of triazole compounds possessing a carbon atom in place of a sulfur atom were efficiently synthesized and their in vitro antifungal activities were investigated. The carbon analogs showed excellent in vitro activity against Candida, Cryptococcus, and Aspergillus species. The MICs of compound 1c against C. albicans ATCC24433, C. neoformans TIMM1855, and A. fumigatus ATCC26430 were 0.016, 0.016, and 0.125 microg/mL, respectively (MICs of fluconazole: 0.5, >4, and >4 microg/mL; MICs of itraconazole: 0.125, 0.25, and 0.25 microg/mL).     

焦性没食子酸联合唑类药物对念珠菌的抑菌作用

目的了解光滑念珠菌临床菌株的药敏情况以及中药单体焦性没食子酸联合唑类药物对念珠菌的抑菌作用。方法收集临床分离的光滑念珠菌116株、白念珠菌49株、热带念珠菌42株、克柔念珠菌4株和近平滑念珠菌13株,采用ATB FUNGUS3药敏试条检测光滑念珠菌的药敏情况;同时采用棋盘肉汤稀释法检测焦性没食子酸联合唑类药物对念珠菌的抑菌情况。结果116株光滑念珠菌中,14.66%(17株)的菌株对氟康唑耐药,22.41%(26株)对伊曲康唑表现为非野生型和81.03%(94株)对伏立康唑表现为非野生型。焦性没食子酸对5种念珠菌的抑菌情况,46.55%光滑念珠菌的MIC值为64μg/mL;34.69%白念珠菌的MIC值为64μg/mL;59.52%热带念珠菌的MIC值为64μg/mL;25%克柔念珠菌的MIC值为128μg/mL;46.15%近平滑念珠菌的MIC值为128μg/mL。唑类药物与焦性没食子酸联合用药时,100%、99.14%、99.14%的光滑念珠菌分别对氟康唑、伊曲康唑和伏立康唑表现为协同作用或相加作用,差异无统计学意义(P>0.05);而白念珠菌、热带念珠菌、克柔念珠菌和近平滑念珠菌均表现为无关作用和拮抗作用。与单独用药相比,联合用药时81.03%、68.1%、77.59%的光滑念珠菌分别对氟康唑、伊曲康唑、伏立康唑的MIC值降低2~3个浓度梯度,且耐药组与非耐药组之间差异具有统计学意义(P<0.05)。结论光滑念珠菌对唑类药物具有耐药性,伏立康唑非野生型菌株所占比例最高。焦性没食子酸单独用药时,5组念珠菌中对光滑念珠菌的抑菌效果最好,且敏感组比耐药组的抑菌效果更加显著。焦性没食子酸联合唑类药物显著降低了光滑念珠菌唑类药物的MIC值,且耐药组比非耐药组的效果更加显著,为中西医结合治疗临床光滑念珠菌感染提供实验依据。     

Comparative study of potential virulence factors in human pathogenic and saprophytic Trichoderma longibrachiatum strains

Potential virulence factors of 9 saprophytic and 12 clinical Trichoderma longibrachiatum strains were examined in the present study, in order to compare their capacity to cause infection in humans. All of the strains were able to grow at temperatures up to 40 degrees C and at pH values ranging from 2.0 to 9.0. Carbon and nitrogen source utilization experiments revealed that all of the strains were able to utilize a series of basic amino acids both as sole carbon and nitrogen sources. The MIC values of the tested antifungal drugs were found to be 0.016-8 microg/ml for amphotericin B, 64-256 microg/ml for fluconazole, 0.5-32 microg/ml for itraconazole and 0.008-1 microg/ml for ketoconazole in the case of the examined isolates. Metabolites of the strains inhibited the growth of different bacteria, furthermore, compounds produced by three clinical isolates reduced the motility of boar spermatozoa, indicating their toxicity to mammalian cells as well. On the whole, there were no significant differences in the examined features between strains derived from clinical or soil samples. The question, however, whether all environmental Trichoderma longibrachiatum strains have the capacity to cause infections or not, remains still unanswered.