Antifungal susceptibility testing of dermatophytes: establishing a medium for inducing conidial growth and evaluation of susceptibility of clinical isolates

Antifungal Susceptibility of Yeasts and Filamentous Fungi by CLSI Broth Microdilution Testing

Antifungal susceptibility testing is performed against yeasts and filamentous fungi (molds) for various purposes. In clinical settings, the results of these in vitro assays may be used to help guide therapy for individual patients. Surveillance studies use susceptibility testing to monitor for the development of resistance to different agents. These assays are also frequently used in preclinical drug development to determine the spectrum of activity and assess the in vitro potency of investigational agents. Broth microdilution is a form of antifungal susceptibility testing that is frequently used for each of these purposes. The Clinical and Laboratory Standards Institute (CLSI) has developed standardized methods for broth microdilution antifungal susceptibility testing of both yeasts and molds. These methods are useful in the clinical diagnostics arena for determining if a particular fungal isolate may be resistant to clinically available antifungals, and they are also amendable for research purposes, as the microtiter trays can be prepared in different formats with different antifungal and investigational agent concentration ranges and with different growth media if necessary. This chapter describes the CLSI methods for antifungal susceptibility testing by broth microdilution for both yeasts and molds, how endpoints are read for different classes of antifungal agents, and how the results may be interpreted.

Dermatophytic infection and in vitro activities of antifungal drugs against dermatophytes in rural India

Background Increase in resistance to conventional antifungals renders the need for antifungal sensitivity testing in Dermatophytes.   The present study aimed at determining the prevalence of dermatophytic infections and their susceptibility pattern in a rural healthcare facility. Methods Patients with suspected dermatophytosis attending the dermatology outpatient department were enrolled in the study. Specimen collection for mycological examinations was done. In-vitro antifungal sensitivity testing was performed as per the Clinical and Laboratory Standard Institute (CLSI) M38-A2 (2008) standards with broth microdilution method. Results Onychomycosis was the commonest (41.9%) presentation. Dermatophytic prevalence based on culture was 110 (70.9%). The commonest species was Trichophyton rubrum (36.8%). Terbinafine was found to be the most effective drug, followed by ketoconazole and itraconazole. Conclusion Antifungal sensitivity in dermatophytic infections should be made a routine in tertiary healthcare facilities as we are already witnessing the rampage of emerging fungal infection– Mucormycosis in the nation and worldwide.

Comparison of Four Methods for the in vitro Susceptibility Testing of Dermatophytes

Objectives

Infections caused by dermatophytes affect a high percentage of the population. Antifungal susceptibility testing (AST) can offer useful information about the susceptibility profiles of the pathogens as well as the concomitant documentation of the appropriate treatment. However, the slow growth rate of these fungi and their poor sporulation are factors that can delay and affect the performance of the AST. The proposed methods by the CLSI or the EUCAST are both laborious for the everyday routine. There are alternative applications which propose the use of an inoculum, consisting of a conidia-mycelium mixture or even plain mycelia, as well as the use of resazurin in order to facilitate the reading. The aim of this study was to compare these approaches to the EUCAST method and evaluate their performance.

Methods

Three alternative methods were compared to the EUCAST proposed methodology for conidia forming molds. The last was defined as the reference method. The methods under evaluation were (a) a fragmented mycelia method, (b) the EUCAST method with the addition of resazurin sodium salt solution and (c) the fragmented mycelia method with the addition of resazurin sodium salt solution. Twenty-two isolates (8 Trichophyton interdigitale, 8 T. rubrum, and 6 Microsporum canis) were tested against the antifungal agents of griseofulvin, terbinafine, fluconazole, and itraconazole.

Results

The essential agreement between the methods was calculated in percentages and a statistical analysis of the results was performed. Data evaluation revealed sufficient overall agreement of the methods with the addition of resazurin to the initial “uncolored” methods (98.9 and 97.5% for the EUCAST and the fragmented mycelia methods, respectively). The fragmented mycelia method exhibited a relatively sufficient overall agreement in comparison to the EUCAST method (90%) and not a satisfactory correlation, probably as a result of various issues of standardization.

Conclusion

The EUCAST method was found to be the more reliable one, whereas the addition of resazurin sodium salt solution facilitates the reading and provides a reliable and objective evaluation. The fragmented mycelia method could serve as an alternative that should be applied only in cases of poor or no sporulating dermatophytes.

Rosemary (Rosmarinus officinalis L., syn Salvia rosmarinus Spenn.) and Its Topical Applications: A Review

Topical application is an important administration route for drugs requiring local action on the skin, thereby avoiding their systemic absorption and adverse side effects. Rosmarinus officinalis L. (syn. Salvia rosmarinus Spenn.), popularly known as rosemary, is an aromatic plant with needle-like leaves belonging to the Lamiaceae family. Rosemary has therapeutic properties and has been used in the folk medicine, pharmaceutical, and cosmetics industries, mainly for its antioxidant and anti-inflammatory properties, which are attributed to the presence of carnosol/carnosic and ursolic acids. The therapeutic use of rosemary has been explored for the treatment of inflammatory diseases; however, other uses have been studied, such as wound healing and skin cancer and mycoses treatments, among others. Besides it therapeutic uses, rosemary has potential applications in cosmetic formulations and in the treatment of pathological and non-pathological conditions, such as cellulite, alopecia, ultraviolet damage, and aging. This review aims to critically discuss the topical applications of rosemary found in the literature while also offering relevant information for the development of topical formulations of its bioactive compounds.

Onychomycosis Unresponsive to Antifungals: Etiology and Treatment with a New Direct Technique

Aims and Objectives:

The aim of this study was to identify the fungal agents causing onychomycosis that were unresponsive to antifungal treatment and to treat these cases by placing under-nail cushions with a mild keratolytic to clear the fungus-invaded tissue.

Materials and Methods:

Fungal agents were identified by the matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) technique.

Results:

Nine patients had Aspergillus spp. (7 Aspergillus niger, 2 Aspergillus flavus); four had Candida species and one had Trichophyton rubrum. All patients were free of infection at the end of treatment.

Conclusion:

As per the results, we may state that onychomycosis that is unresponsive to treatment in immunocompetent patients seems to be mostly associated with molds. Direct application of a mild keratolytic to the fungus-invaded part, e.g., the nail plate and/or nail bed and removal of fungal elements may provide a successful treatment outcome.

Trichophyton rubrum Azole Resistance Mediated by a New ABC Transporter, TruMDR3

The mechanisms of terbinafine resistance in a set of clinical isolates of Trichophyton rubrum have been studied recently. Of these isolates, TIMM20092 also showed reduced sensitivity to azoles. The azole resistance of TIMM20092 could be inhibited by milbemycin oxime, prompting us to examine the potential of T. rubrum to develop resistance through multidrug efflux transporters.

The mechanisms of terbinafine resistance in a set of clinical isolates of Trichophyton rubrum have been studied recently. Of these isolates, TIMM20092 also showed reduced sensitivity to azoles. The azole resistance of TIMM20092 could be inhibited by milbemycin oxime, prompting us to examine the potential of T. rubrum to develop resistance through multidrug efflux transporters. The introduction of a T. rubrum cDNA library into Saccharomyces cerevisiae allowed the isolation of one transporter of the major facilitator superfamily (MFS) conferring resistance to azoles (TruMFS1). To identify more azole efflux pumps among 39 ABC and 170 MFS transporters present within the T. rubrum genome, we performed a BLASTp analysis of Aspergillus fumigatus, Candida albicans, and Candida glabrata on transporters that were previously shown to confer azole resistance. The identified candidates were further tested by heterologous gene expression in S. cerevisiae. Four ABC transporters (TruMDR1, TruMDR2, TruMDR3, and TruMDR5) and a second MFS transporter (TruMFS2) proved to be able to operate as azole efflux pumps. Milbemycin oxime inhibited only TruMDR3. Expression analysis showed that both TruMDR3 and TruMDR2 were significantly upregulated in TIMM20092. TruMDR3 transports voriconazole (VRC) and itraconazole (ITC), while TruMDR2 transports only ITC. Disruption of TruMDR3 in TIMM20092 abolished its resistance to VRC and reduced its resistance to ITC. Our study highlights TruMDR3, a newly identified transporter of the ABC family in T. rubrum, which can confer azole resistance if overexpressed. Finally, inhibition of TruMDR3 by milbemycin suggests that milbemycin analogs could be interesting compounds to treat dermatophyte infections in cases of azole resistance.

Recent Findings in Onychomycosis and Their Application for Appropriate Treatment

Onychomycosis is mainly caused by two dermatophyte species, Trichophyton rubrum and Trichophyton interdigitale. A study of nail invasion mechanisms revealed that the secreted subtilisin Sub6, which has never been detected under in vitro growth conditions, was the main protease secreted by T. rubrum and T. interdigitale during infection. In contrast, most of the proteases secreted during the digestion of keratin in vitro were not detected in infected nails. The hypothesis that proteases isolated from dermatophytes grown in a keratin medium are virulence factors is no longer supported. Non-dermatophyte fungi can also be infectious agents in nails. It is necessary to identify the infectious fungus in onychomycosis to prescribe adequate treatment, as moulds such as Fusarium spp. and Aspergillus spp. are insensitive to standard treatments with terbinafine or itraconazole, which are usually applied for dermatophytes. In these refractory cases, topical amphotericin B treatment has shown to be effective. Terbinafine treatment failure against dermatophytes is also possible, and is usually due to resistance caused by a missense mutation in the squalene epoxidase enzyme targeted by the drug. Trichophyton resistance to terbinafine treatment is an emerging problem, and a switch to azole-based treatment may be necessary to cure such cases of onychomycosis.

Therapy and Antifungal Susceptibility Profile of Microsporum canis

Microsporum canis is a worldwide diffused zoophilic dermatophyte which causes clinical conditions often characterised by multifocal alopecia, scaling, and circular lesions in many animal species, including humans. A large variety of oral and topical antifungal protocols is available for treating M. canis infection. However, the efficacy of these drugs and treatment protocols is variable, with treatment failure up to 40% of patients possibly due to resistance phenomena. The lack of standardised reference methods for evaluating the antifungal susceptibility of M. canis represents a major hindrance in assessing microbiological resistance in unresponsive clinical cases. Therefore, data about conventional therapy against M. canis and the protocols employed to test the antifungal activity of the most commonly employed drugs (i.e., azoles, polyenes, allylamines, and griseofulvin) have been summarised herein. This article focuses on technical parameters used for antifungal susceptibility tests, their effects on the minimum inhibitory concentration value, as well as their clinical implications.

A "Hole Punched Plate" method for easy generation and harvesting of microconidia in the dermatophyte Trichophyton rubrum

Handling of the medically important dermatophyte Trichophyton rubrum in the laboratory typically requires the generation of spores — for storage, treatment and plating when needed. The described method allows technically simple but efficient generation and harvesting of microconidia by cutting holes in Sabouraud dextrose agar medium that is covered by a mature T. rubrum mycelium.

Antifungal Resistance in Dermatology

Cutaneous fungal infections affect more than one-fourth of world's population. The pathogenesis and severity of fungal infection depend on various immunological and nonimmunological factors. The rampant use of antifungal therapy in immunocompromised individuals marked the onset of antifungal drug resistance. Fungal resistance can be microbiological or clinical. Microbiological resistance depends on various fungal factors which have established due to genetic alteration in the fungi. Clinical resistance is due to host- or drug-related factors. All these factors may cause fungal resistance individually or in tandem. In addition to standardized susceptibility testing and appropriate drug dosing, one of the ways to avoid resistance is the use of combinational antifungal therapy. Combination therapy also offers advantages in increased synergistic action with enhanced spectrum activity. Newer insights into mechanisms of drug resistance will help in the development of appropriate antifungal therapy.

In Vitro Antifungal Activity of Hexahydropyrimidine Derivatives against the Causative Agents of Dermatomycosis

Nitrogenated heterocyclic compounds are present in both natural and synthetic drugs, and hexahydropyrimidine derivatives may prove to be efficient in treating dermatomycosis causing fungi. This study evaluated the antifungal activity of four hexahydropyrimidine derivatives against the dermatomycosis causing fungi. These derivatives were synthesized, characterized, and assessed in terms of their activity against Trichophyton mentagrophytes, Microsporum canis, Microsporum gypseum, Trichophyton rubrum, Fusarium oxysporum, and Epidermophyton floccosum between concentrations 7.8 and 1,000 μg mL⁻¹. Scanning electron micrographs were assessed for the active derivatives and reference drugs, and these micrographs revealed that new agents cause morphological changes in fungi. The derivatives HHP1, HHP3, and HHP4 revealed poor activity against the four fungal strains (MICs range 500–1000 μg mL⁻¹). Compound HHP3 was found to be the best potential antifungal agent among those tested and was the most effective among all the active derivatives that caused morphological changes in the susceptible strains.

Molecular Identification and Antifungal Susceptibility Patterns of Clinical Dermatophytes Following CLSI and EUCAST Guidelines

Dermatophytes are associated with superficial infections in humans worldwide. The aim of the present study was to determine the species distribution and susceptibility patterns of clinical dermatophytes. Samples received for routine mycological processing from 124 suspected cases attending a dermatologic clinic in a tertiary care hospital were included in the study. On direct microscopy, 74.1% (92/124) were positive and 53.2% (66/124) grew on culture. The isolates were comprised of Trichophytoninterdigitale (56%) followed by Trichophytontonsurans (25.7%), Trichophytonrubrum (7.5%), Trichophytonviolaceum (4.5%), Microsporumgypseum (4.5%), and Trichophytonverrucosum (1.5%). Conventional mycological identification was concordant with ITS sequencing except for T.mentagrophytes. High minimum inhibitory concentration (MIC) values (geometric mean, >1 µg/mL) were observed for T.tonsurans and T.rubrum to terbinafine and griseofulvin. This study highlights the shift in epidemiology from T.rubrum to T.interdigitale. It also raises a concern of high MICs of terbinafine and griseofulvin among our isolates. Surveillance of antifungal susceptibility patterns can provide clinicians with local MIC data that can further aid in guiding better management in relapse cases of dermatomycosis.

Determination of minimum inhibitory concentrations of itraconazole, terbinafine and ketoconazole against dermatophyte species by broth microdilution method

PURPOSE

Various antifungal agents both topical and systemic have been introduced into clinical practice for effectively treating dermatophytic conditions. Dermatophytosis is the infection of keratinised tissues caused by fungal species of genera Trichophyton, Epidermophyton and Microsporum, commonly known as dermatophytes affecting 20-25% of the world's population. The present study aims at determining the susceptibility patterns of dermatophyte species recovered from superficial mycoses of human patients in Himachal Pradesh to antifungal agents; itraconazole, terbinafine and ketoconazole. The study also aims at determining the minimum inhibitory concentrations (MICs) of these agents following the recommended protocol of Clinical and Laboratory Standards Institute (CLSI) (M38-A2).

METHODOLOGY

A total of 53 isolates of dermatophytes (T. mentagrophyte-34 in no., T. rubrum-18 and M. gypseum-1) recovered from the superficial mycoses were examined. Broth microdilution method M38-A2 approved protocol of CLSI (2008) for filamentous fungi was followed for determining the susceptibility of dermatophyte species.

RESULTS

T. mentagrophyte isolates were found more susceptible to both itraconazole and ketoconazole as compared to terbinafine (MIC50: 0.125 µg/ml for itraconazole, 0.0625 µg/ml for ketoconazole and 0.5 µg/ml for terbinafine). Three isolates of T. mentagrophytes (VBS-5, VBSo-3 and VBSo-73) and one isolate of T. rubrum (VBPo-9) had higher MIC values of itraconazole (1 µg/ml). Similarly, the higher MIC values of ketoconazole were observed in case of only three isolates of T. mentagrophyte (VBSo-30 = 2 µg/ml; VBSo-44, VBM-2 = 1 µg/ml). The comparative analysis of the three antifungal drugs based on t-test revealed that 'itraconazole and terbinafine' and 'terbinafine and ketoconazole' were found independent based on the P < 0.005 in case of T. mentagrophyte isolates. In case of T. rubrum, the similarity existed between MIC values of 'itraconazole and ketoconazole' and 'terbinafine and ketoconazole'.

CONCLUSION

The MIC values observed in the present study based on standard protocol M38-A2 of CLSI 2008 might serve as reference for further studies covering large number of isolates from different geographic regions of the state. Such studies might reflect on the acquisition of drug resistance among isolates of dermatophyte species based on MIC values.

Antifungal susceptibility and virulence factors of clinically isolated dermatophytes in Tehran, Iran

BACKGROUND AND OBJECTIVES

Dermatophytes possess a wide array of virulence factors and various antifungal susceptibility patterns which influence their pathogenesis in humans and animals. The aim of this study was to evaluate antifungal susceptibility and keratinase and proteinase activity of 49 dermatophyte strains from the genera Microsporum, Trichophyton and Epidermophyton which were isolated from human cases of dermatophytosis.

MATERIALS AND METHODS

Forty-nine dermatophyte strains isolated from clinical samples were cultured on general and specific culture media. Keratinase and proteinase activity was screened on solid mineral media and confirmed in liquid cultures. Drug susceptibility toward azoles (fluconazole, ketoconazole and itraconazole), griseofulvin and terbinafine was evaluated using disk diffusion method on Mueller-Hinton agar and minimum inhibitory concentrations (MICs) were determined using microbroth dilution assay according to the Clinical and Laboratory Standards Institute (CLSI) guidelines.

RESULTS

Our results indicated that clinically isolated dermatophytes from 7 major species produced keratinase and proteinase at different extents. The mean keratinase and proteinase activity was reported as 6.69 ± 0.31 (U/ml) and 2.10 ± 0.22 (U/ml) respectively. Disk diffusion and microbroth dilution (MIC) results of antifungal susceptibility testing showed that ketoconazole was the most effective drug against Epidermophyton floccosum and Trichophyton mentagrophytes, itraconazole against T. rubrum and E. floccosum, and griseofulvin and terbinafine against Trichophyton verrucosum. Our results showed that all dermatophyte isolates were resistant to fluconazole. Overall, ketoconazole and itraconazole were the most effective drugs for all dermatophyte species tested.

CONCLUSION

Our results showed that antifungal susceptibility testing is an urgent need to select drugs of choice for treatment of different types of dermatophytosis and further indicated the importance of keratinase and proteinase in pathogenesis of dermatophyte species.

Evaluation of local trace element status and 8-Iso-prostaglandin F2α concentrations in patients with Tinea pedis

Background

Tinea pedis (TP) is an infection of the feet caused by fungi. The infectious diseases caused by dermatophytes are mainly related to the enzymes produced by these fungi. Up to the now, the local 8-iso-prostaglandin F_2α (8-iso-PGF_2α), concentration as oxidative stress biomarker and trace elements status have not been published in patients with TP. The aim of this study is to evaluate the relationship between oxidative stress and trace elements (Cu, Zn, Se), and to evaluate the ratios of Cu/Zn and Cu/Se in this disorder.

Methods

Forty-three consecutive patients with a diagnosis of unilateral interdigital TP were enrolled in this study. The samples were obtained by scraping the skin surface. 8-iso-PGF_2α concentrations in scraping samples were determined by ELISA. In addition, the levels of Se, Zn and Cu in scraping samples were determined on flame and furnace atomic absorption spectrophotometer using Zeeman background correction.

Results

Oxidative stress was confirmed by the significant elevation in 8-iso-PGF_2α concentrations (p < 0.05). When compared to non-lesional area, Zn and Se levels were significantly lower on lesional area, whereas Cu levels was higher on the lesional area than the non-lesional area (p < 0.05). In addition, the correlation results of this study were firstly shown that there were significant and positive correlations between Cu and 8-iso-PGF_2α parameters, but negative correlations between Se-Cu; Se-8-iso-PGF_2α parameters in lesional area. Furthermore, the ratios of Cu/Zn and Cu/Se were significantly higher on the lesional area than the non-lesional area (p < 0.05). According to sex and fungal subtypes, there was no significant difference in the concentrations of 8-iso-PGF_2α and trace elements in patients with TP (p > 0.05).

Conclusions

Our results showed that there is a possible link between oxidative stress (increased 8-iso-PGF_2α concentrations) and imbalanced of trace elements status in lesional area of TP patients. The use of antifungal agents together with both Zn and Se drugs could be helpful in the both regression of disease and in shortening the duration of disease.

Progressive development in experimental models of transungual drug delivery of anti-fungal agents

Pre-clinical development comprises of different procedures that relate drug discovery in the laboratory for commencement of human clinical trials. Pre-clinical studies can be designed to recognize a lead candidate from a list to develop the procedure for scale-up, to choose the unsurpassed formulation, to determine the frequency, and duration of exposure; and eventually make the foundation of the anticipated clinical trial design. The foremost aim in the pharmaceutical research and industry is the claim of drug product quality throughout a drug's life cycle. The particulars of the pre-clinical development process for different candidates may vary; however, all have some common features. Typically in vitro, in vivo or ex vivo studies are elements of pre-clinical studies. Human pharmacokinetic in vivo studies are often supposed to serve as the 'gold standard' to assess product performance. On the other hand, when this general assumption is revisited, it appears that in vitro studies are occasionally better than in vivo studies in assessing dosage forms. The present review is compendious of different such models or approaches that can be used for designing and evaluation of formulations for nail delivery with special reference to anti-fungal agents.

Antifungal activity of four honeys of different types from Algeria against pathogenic yeast: Candida albicans and Rhodotorula sp

OBJECTIVE

To evaluate the antifungal activity of four honeys of different types from Algeria against pathogenic yeast i.e. Candida albicans (C. albicans) and Rhodotorula sp.

METHODS

Four Algeria honeys of different botanical origin were analyzed to test antifungal effect against C. albicans, and Rhodotorula sp. Different concentrations (undiluted, 10%, 30%, 50% and 70% w/v) of honey were studied in vitro for their antifugal activity using C. albicans and Rhodotorula sp. as fungal strains.

RESULTS

The range of the diameter of zone of inhibition of various concentrations of tested honeys was (7-23 mm) for Rhodotorula sp., while C. albicans showed clearly resistance towards all concentrations used. The MICs of tested honey concentrations against C. albicans and Rhodotorula sp. were (70.09-93.48)% and (4.90-99.70)% v/v, respectively.

CONCLUSIONS

This study demonstrates that, in vitro, these natural products have clearly an antifungal activity against Rhodotorula sp. and C. albicans.

Antifungal and antioxidant activity of Crassocephalum bauchiense (Hutch.) Milne-Redh ethyl acetate extract and fractions (Asteraceae)

BACKGROUND

Crassocephalum bauchiense is a flowering plant, found in the West Region of Cameroon. Previous studied has highlighted the antibacterial and the dermal toxicological safety as well as the immunomodulatory activities of the ethyl acetate extract of its dry leaves. As an extension of the previous researches, the current work has been undertaken to evaluate the in vitro antifungal and antioxidant activities of C. bauchiense dried leaves ethyl acetate extract and fractions.

METHODS

The extract was obtained by maceration in ethyl acetate and further fractionated into six fractions labeled F1 to F6 by flash chromatography. The antifungal activity of the extract and fractions against yeasts and dermatophytes was evaluated using broth microdilution method. Antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and β-carotene - linoleic acid assays.

RESULTS

The extract (MIC = 0.125 - 4 mg/ml) was found to be more active on dermatophytes and yeasts compared to the fractions. The ethyl acetate extract and fractions exhibited strong scavenging activity on DPPH (CI50 = 28.57 - 389.38 μg/ml). The fractions F3 and F6 expressed best antioxidant activity on DPPH radicals compared to the crude extract.

CONCLUSION

The results of these findings clearly showed that C. bauchiense ethyl acetate extract has a significant antifungal and antioxidant activity. It is therefore a source of active compounds that might be used as antifungal and antioxidant agents.

Evaluation of Antifungal Efficacy in an Optimized Animal Model ofTrichophytonmentagrophytes-Dermatophytosis

Dermatophytoses are known to cause considerable discomfort, cosmetic problems and financial loss that have been recognized as a significant health concern worldwide. Since currently available antifungal agents have limitations in their efficacy, new agents are being developed. This study was undertaken to optimize an in vivo model of experimental dermatophytosis for evaluation of the efficacy of antifungal compounds. Guinea pigs were infected with different inocula of T. mentagrophytes to establish dermatophytosis. The optimal conditions for dermatophytosis in guinea pigs were found to be an inoculum size of 1 x 10(7) fungal cells applied on abraded skin. After optimization, animals were treated with oral or topical formulations of terbinafine. The optimized guinea pig model was found to be highly reproducible, and useful in the primary screening and evaluation of the anti-dermatophytic efficacy of topical and oral formulations of antifungal agents.

Antioxidant and anti-dermatophytic properties leaf and stem bark of Xylosma longifolium clos

BACKGROUND

The present study was carried out to assess the phytochemical and anti-dermatophytic effect of the leaf and bark extracts of Xylosma longifolium Clos. The leaf and stem bark are used by the indigenous people of Manipur, India for treatment of skin diseases.

METHODS

The leaves and stem barks of Xylosma longifolium were extracted using petroleum ether, chloroform and methanol respectively. The different extracts of each plant parts were tested for antioxidant activity using DPPH assay. The phenolic content was assayed using Folin-Ciocalteu colorimetric method. Each extracts was further analysed by RP-HPLC to quantify some individual flavonoid components. The anti-dermatophytic activity was evaluated both by agar diffusion method and micro wells dilution method against the Microsporum boullardii MTCC 6059, M. canis (MTCC 2820 and MTCC 32700), M. gypseum MTCC 2819, Trichophyton ajelloi MTCC 4878, T. rubrum (MTCC 296 and MTCC 3272).

RESULTS

The free radical scavenging activity values were ranged from 0.7 to 1.41 mg/ml and 0.6 to 1.23 mg/ml, respectively for leaf and stem bark extracts. The amount of total phenolic contents of the extracts occurred in both leaf and bark in the range of 12 to 56.6 mg GAE/100 g and 16 to 58 mg GAE/100 g respectively. RP-HPLC analysis for flavonoids revealed the presence of two major flavonoid compounds, rutin and catechin. Kaempferol was in trace or absent. Methanol leaf extract showed significant low inhibitory effect against tested fungus Trichophyton ajelloi MTCC 4878 (0.140625 mg/ml) as the most sensitive. These finding suggest that the methanol leaf extract tested contain compounds with antimicrobial properties.

CONCLUSION

The results of our study may partially justify the folkloric uses on the plant studied and further provide an evidence that the leaf extract of Xylosma longifolium might be indeed a potential sources of antimicrobial agents.

Expression, purification, and enzymatic characterization of Bombyx mori nucleopolyhedrovirus DNA polymerase

Bombyx mori nucleopolyhedrovirus (BmNPV) is a major viral agent that causes deadly grasserie disease in silkworms. BmNPV DNA polymerase (Bm-DNAPOL), encoded by the ORF53 gene, plays a central role in viral DNA replication. In this work, a His-tagged Bm-DNAPOL fusion protein, constructed using a novel MultiBac expression system, was overexpressed in Sf-9 insect cells, purified to near homogeneity on Ni-NTA agarose beads and further purified by ion-exchange chromatography. About 0.4 mg of enzyme was obtained from about 1 × 10(9) infected Sf-9 cells in suspension culture. Characterization of the highly purified enzyme indicated that Bm-DNAPOL is a monomer with an apparent molecular mass of approximately 110,000 Da. It possessed a specific activity of 15,126.3 U/mg under optimal in vitro reaction conditions and behaved in the manner of a proliferating cell nuclear antigen (PCNA)-independent DNA polymerase on both poly(dA)/oligo(dT) primer/template and singly premiered M13 DNA. BmNPV viral replication may be independent of replication factor C and a PCNA complex, while single-stranded DNA binding protein might play an important role in BmNPV DNA replication. These findings will be significant in studies on BmNPV-based disease in silkworms and for using silkworms as a bioreactor for the production of biomolecules of commercial importance.

Infected nail plate model made of human hair keratin for evaluating the efficacy of different topical antifungal formulations against Trichophyton rubrum in vitro

A novel model of infected nail plate for testing the efficacy of topical antifungal formulations has been developed. This model utilized keratin film made of human hair keratin as a nail plate model. Subsequent to infection by Trichophyton rubrum, the common causative agent of onychomycosis, keratin films as infected nail plate models were treated with selected topical formulations, that is cream, gel, and nail lacquer. Bovine hoof was compared to keratin film. In contrast to the common antifungal susceptibility test, the antifungal drugs tested were applied as ready-to-use formulations because the vehicle may modify and control the drug action both in vitro and in vivo. Extrapolating the potency of an antifungal drug from an in vitro susceptibility test only would not be representative of the in vivo situation since these drugs are applied as ready-to-use formulations, for example as a nail lacquer. Although terbinafine has been acknowledged to be the most effective antifungal agent against T. rubrum, its antifungal efficacy was improved by its incorporation into an optimal formulation. Different gels proved superior to cream. Therefore, this study is able to discriminate between efficacies of different topical antifungal formulations based on their activities against T. rubrum.

Alkylphenol Activity against Candida spp. and Microsporum canis: A Focus on the Antifungal Activity of Thymol, Eugenol and O-Methyl Derivatives

In recent years there has been an increasing search for new antifungal compounds due to the side effects of conventional antifungal drugs and fungal resistance. The aims of this study were to test in vitro the activity of thymol, eugenol, estragole and anethole and some O-methyl-derivatives (methylthymol and methyleugenol) against Candida spp. and Microsporum canis. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC). The minimum fungicidal concentrations (MFC) for both Candida spp. and M. canis were found by subculturing each fungal suspension on potato dextrose agar. Thymol, methylthymol, eugenol, methyl-eugenol, anethole, estragole and griseofulvin respectively, presented the following MIC values against M. canis: 4.8–9.7; 78–150; 39; 78–150; 78–150; 19–39 µg/mL and 0.006–2.5 μg/mL. The MFC values for all compounds ranged from 9.7 to 31 µg/mL. Concerning Candida spp, thymol, methylthymol, eugenol, methyleugenol, anethole, estragole and amphotericin, respectively, showed the following MIC values: 39; 620–1250; 150–620; 310–620; 620; 620–1250 and 0.25–2.0 μg/mL. The MFC values varied from 78 to 2500 µg/mL. All tested compounds thus showed in vitro antifungal activity against Candida spp. and M. canis. Therefore, further studies should be carried out to confirm the usefulness of these alkylphenols in vivo.

Two antifungal components isolated from Fructus Psoraleae and Folium Eucalypti Globuli by bioassay-guided purification

Fructus Psoraleae and Folium Eucalypti Globuli have long been used as Chinese medicines to treat various ailments such as asthma, eczema and dermatomycosis. In previous studies, their antifungal activities were demonstrated. The aim of the present study was to isolate active antidermatophytic compounds from their ethanolic extracts by means of bioassay-guided purification. Guided by the inhibitory activities on Trichophyton mentagrophytes, Trichophyton rubrum and Paecilomyces variotii, bakuchiol was isolated from the n-hexane fraction of Fructus Psoraleae whilst macrocarpal C was isolated from the n-hexane fraction of Folium Eucalypti Globuli. Both pure compounds could effectively inhibit the growth of dermatophytes in vitro. This is the first paper to report the isolation and identification of active antidermatophytic compounds from Fructus Psoraleae and Folium Eucalypti Globuli by the bioassay-guided purification.

Antioxidant and antidermatophytic activities of essential oil and extracts of Magnolia liliflora Desr

This study was carried out to assess the antioxidant and antidermatophytic activities of the essential oil and extracts of Magnolia liliflora Desr. Antioxidant activity was evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The free radical scavenging activities of the oil and ethyl acetate extract were found to be superior (IC(50) values=10.11 and 16.17 microg/ml, respectively) as compared to butylatedhydreoxyanisole (BHA), (IC(50) value=18.27 microg/ml). Also the ethyl acetate extract revealed the highest phenolic contents (96.13 mg/g of dry wt) as compared to the other extracts. Further, the oil (1000 microg/disc) and extracts (1500 microg/disc) revealed 42.36-63.12% and 19.07-54.14% antidermatophytic effect, respectively along with their respective MIC values ranging from 62.5 to 500 and 250 to 2000 microg/ml against the members of Trichophyton and Microsporum spp. Also the oil had strong detrimental effect on spore germination of tested fungal pathogens as well as concentration and time dependent kinetic inhibition of Microsporum canis KCTC 6348. The results of this study justify a potential role of M. liliflora to serve as a natural antioxidant and antidermatophytic agent.

Testing of antifungal combinations against yeasts and dermatophytes

BACKGROUND

Fungal infections of the nail are a common and chronic problem. The main pathogens responsible for onychomycosis are dermatophytes, yeasts and moulds. Despite significant improvements, approximately 20% of patients with onychomycosis still fail on antifungal therapy. The successful exploitation of drug synergy may provide a useful approach to improve cure rates.

METHODS

The minimum inhibitory concentrations (MIC(80)) were recorded for pathogens that are most frequently responsible for onychomycosis against combinations of several antifungal agents, namely, fluconazole, itraconazole, terbinafine and amorolfine. Fractional inhibitory concentrations (FICs) were then calculated from the MIC(80) results and the FIC values for each drug in the combinations added to determine the degree of synergy. A combined value of <1 was taken to suggest synergy; a value of 1-2 indicated an additive effect or indifference; and a combined FIC value of >2 was taken to suggest antagonism.

RESULTS

Overall, 46% of amorolfine combinations showed results suggestive of synergy, with the most synergistic results seen against dermatophytes (54%) and moulds (52%).

CONCLUSIONS

Some combinations of drugs may have synergistic activity in vitro; however, the importance of this in a clinical setting is yet to be established, and more studies are justified.

Comparison of in vitro activity of five antifungal agents against dermatophytes, using the agar dilution and broth microdilution methods

The purpose of this study was to compare the agar dilution and broth microdilution methods for determining the minimum inhibitory concentration (MIC) of fluconazole, itraconazole, ketoconazole, griseofulvin and terbinafine for 60 dermatophyte samples belonging to the species Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum canis. The percentage agreement between the two methods, for all the isolates with < 2 dilutions that were tested was 91.6% for ketoconazole and griseofulvin, 88.3% for itraconazole, 81.6% for terbinafine and 73.3% for fluconazole. One hundred percent agreement was obtained for Trichophyton mentagrophytes isolates evaluated with ketoconazole and griseofulvin. Thus, until a reference method for testing the in vitro susceptibility of dermatophytes is standardized, the similarity of the results between the two methods means that the agar dilution method may be useful for susceptibility testing on these filamentous fungi.

Antifungal and marker effects of Talisia esculenta lectin on Microsporum canis in vitro

AIMS

The purpose of this study was to demonstrate the usefulness of lectin obtained from Talisia esculenta (TEL) seeds as a tool to recognize and study Microsporum canis. For this purpose, we investigated the antifungal and marker action of this lectin and the relationship of these effects with the presence of carbohydrates on the structure of this fungus.

METHODS AND RESULTS

The in vitro antifungal activity of TEL was analysed by broth microdilution assay. In addition, TEL was assessed against the arthroconidia present on hairs obtained from infected dogs and cats. The affinity of fluorescein isothiocyanate (FITC)-labelled TEL for macroconidia and arthroconidia of M. canis was also tested. The effects of TEL on the growth of the M. canis strains began with 0.125 mg ml(-1), and 100% inhibition was obtained with a concentration of 2 mg ml(-1). The addition of carbohydrates, especially N-acetyl-glucosamine and d-mannose, inhibited these antifungal effects. TEL was able to inhibit the growth of arthroconidial chitin-rich forms of M. canis obtained from hairs of infected animals and strains cultured in Sabouraud agar. FITC-labelled TEL efficiently marked macroconidial and arthroconidial forms of M. canis, as shown by fluorescent microscopy.

CONCLUSIONS

These results show that the inhibitory effects of TEL on M. canis growth may be related to the interaction of lectin with the carbohydrates present at the micro-organism's surface, mainly D-mannose and N-acetyl-glucosamine.

SIGNIFICANCE AND IMPACT OF THE STUDY

Talisia esculenta can be used as an important tool in the biochemical study of M. canis or as a molecule to recognize this dermatophyte in infected tissue.

Leptoglycin: a new Glycine/Leucine-rich antimicrobial peptide isolated from the skin secretion of the South American frog Leptodactylus pentadactylus (Leptodactylidae)

Antimicrobial peptides are components of innate immunity that is the first-line defense against invading pathogens for a wide range of organisms. Here, we describe the isolation, biological characterization and amino acid sequencing of a novel neutral Glycine/Leucine-rich antimicrobial peptide from skin secretion of Leptodactylus pentadactylus named leptoglycin. The amino acid sequence of the peptide purified by RP-HPLC (C(18) column) was deduced by mass spectrometric de novo sequencing and confirmed by Edman degradation: GLLGGLLGPLLGGGGGGGGGLL. Leptoglycin was able to inhibit the growth of Gram-negative bacteria Pseudomonas aeruginosa, Escherichia coli and Citrobacter freundii with minimal inhibitory concentrations (MICs) of 8 microM, 50 microM, and 75 microM respectively, but it did not show antimicrobial activity against Gram-positive bacteria (Staphylococcus aureus, Micrococcus luteus and Enterococcus faecalis), yeasts (Candida albicans and Candida tropicalis) and dermatophytes fungi (Microsporum canis and Trichophyton rubrum). No hemolytic activity was observed at the 2-200 microM range concentration. The amino acid sequence of leptoglycin with high level of glycine (59.1%) and leucine (36.4%) containing an unusual central proline suggests the existence of a new class of Gly/Leu-rich antimicrobial peptides. Taken together, these results suggest that this natural antimicrobial peptide could be a tool to develop new antibiotics.

In vitro susceptibility testing of dermatophytes isolated in Goiania, Brazil, against five antifungal agents by broth microdilution method

The antifungal activities of fluconazole, itraconazole, ketoconazole, terbinafine and griseofulvin were tested by broth microdilution technique, against 60 dermatophytes isolated from nail or skin specimens from Goiania city patients, Brazil. In this study, the microtiter plates were incubated at 28 ºC allowing a reading of the minimal inhibitory concentration (MIC) after four days of incubation for Trichophyton mentagrophytes and five days for T. rubrum and Microsporum canis. Most of the dermatophytes had uniform patterns of susceptibility to the antifungal agents tested. Low MIC values as 0.03 µg/mL were found for 33.3%, 31.6% and 15% of isolates for itraconazole, ketoconazole and terbinafine, respectively.