Application of neutral red staining for evaluation of the viability of dermatophytes and Candida in human skin scales

Prevalence and distribution of dermatophytosis lesions on cattle in Plateau State, Nigeria

Background and Aim:

Dermatophytosis is an infection of the superficial, keratinized structures of the skin, nails, and hair of man and animals caused by a group of fungi called dermatophytes in the genera Trichophyton, Microsporum, and Epidermophyton. The prevalence of dermatophytosis among cattle in Nigeria and Plateau State, in particular, is yet to be fully determined. This study aimed to determine the prevalence and the distribution of dermatophytosis lesions on cattle in Plateau State, Nigeria.

Materials and Methods:

Four hundred and thirty-seven cattle showing visible skin lesions suggestive of dermatophytosis were drawn from nine local government areas (three each) from the three senatorial districts of Plateau State, Nigeria. Skin scrapings were aseptically collected using a cross-sectional study, in which sampling units were selected using purposive sampling method. Samples were processed for both direct microscopic examination and isolation of dermatophytes in culture. The isolates were stained with lactophenol cotton blue and identified microscopically based on the size, shape, and arrangement of macro- and micro-conidia. The dermatophytes were further identified by determining the sequences of the internal transcribed spacer regions of their ribosomal DNA. Data were analyzed and presented as percentages, bar graph, and Chi-square test of association. p≤0.05 was considered statistically significant.

Results:

The overall prevalence rate of bovine dermatophytosis in Plateau State was found to be 11.0%. Trichophyton verrucosum was more frequently isolated (54.2%) than Trichophyton mentagrophytes (45.8%). Age, breed, management practice, and season were significantly associated with the occurrence of the disease (p<0.05).

Conclusion:

Dermatophytosis among cattle may be of public health significance in Plateau State, Nigeria. This is the first report on the prevalence and distribution of dermatophytosis lesions on cattle from Plateau State, Nigeria.

From observational to analytical morphology of the stratum corneum: progress avoiding hazardous animal and human testings

Background

In cosmetic science, noninvasive sampling of the upper part of the stratum corneum is conveniently performed using strippings with adhesive-coated discs (SACD) and cyanoacrylate skin surface strippings (CSSSs).

Methods

Under controlled conditions, it is possible to scrutinize SACD and CSSS with objectivity using appropriate methods of analytical morphology. These procedures apply to a series of clinical conditions including xerosis grading, comedometry, corneodynamics, corneomelametry, corneosurfametry, corneoxenometry, and dandruff assessment.

Results

With any of the analytical evaluations, SACD and CSSS provide specific salient information that is useful in the field of cosmetology. In particular, both methods appear valuable and complementary in assessing the human skin compatibility of personal skincare products.

Conclusion

A set of quantitative analytical methods applicable to the minimally invasive and low-cost SACD and CSSS procedures allow for a sound assessment of cosmetic effects on the stratum corneum. Under regular conditions, both methods are painless and do not induce adverse events. Globally, CSSS appears more precise and informative than the regular SACD stripping.

A modified method to detect the phagocytic ability of eosinophilic and basophilic haemocytes in the oyster Crassostrea plicatula

The immune defence system of bivalve species largely depends on haemocytes. Haemocytes are generally classified as hyalinocytes (H) or granulocytes (G), and each cell type is further sub-classified as eosinophilic (E) or basophilic (B) haemocytes. Until recently, research on eosinophilic and basophilic haemocytes has primarily focused on their morphologies, dye affinities and intracellular components. Few studies have investigated their phagocytic ability because of the absence of appropriate experimental methods. In this study, we introduce a modified method suitable to detect the phagocytic ability of eosinophilic and basophilic haemocytes. This modified method involves neutral red staining by employing fluorescent microspheres as the phagocytosed medium. Specifically, haemocytes are incubated with fluorescent microspheres and then stained with neutral red. Next, the stained haemocytes are fixed by acetone and are counterstained by propidium iodide. Finally, the haemocytes are observed under a multifunctional microscope to analyse the phagocytic ability by counting the number of eosinophilic or basophilic haemocytes involved in phagocytosis (calculation for phagocytic rate, PR) and the number of phagocytosed microspheres by each eosinophilic or basophilic haemocyte (calculation for phagocytic index, PI). By employing this modified method in the oyster Crassostrea plicatula, we found that the PRs of G and H were very similar to the data obtained by another method, flow cytometry, indicating that this modified method has high accuracy. Additionally, we also found that the PR and PI in E-G were 70.9 ± 7.3% and 1.0 ± 0.2, respectively, which were both significantly higher than those in B-G (53.1 ± 6.4% and 0.7 ± 0.1). The PR and PI in E-H were 16.3 ± 2.8% and 0.2 ± 0.1, respectively, while in B-H, the PR and PI were 13.3 ± 3.6% and 0.2 ± 0.1, respectively, with no significant difference observed. Based on this result, eosinophilic granulocytes are more active in phagocytosis than basophilic granulocytes in the oyster immune defence system.

Electrochemical detection of intracellular and cell membrane redox systems in Saccharomyces cerevisiae

Redox mediators can interact with eukaryote cells at a number of different cell locations. While cell membrane redox centres are easily accessible, the redox centres of catabolism are situated within the cytoplasm and mitochondria and can be difficult to access. We have systematically investigated the interaction of thirteen commonly used lipophilic and hydrophilic mediators with the yeast Saccharomyces cerevisiae. A double mediator system is used in which ferricyanide is the final electron acceptor (the reporter mediator). After incubation of cells with mediators, steady state voltammetry of the ferri/ferrocyanide redox couple allows quantitation of the amount of mediator reduced by the cells. The plateau current at 425 mV vs Ag/AgCl gives the analytical signal. The results show that five of the mediators interact with at least three different trans Plasma Membrane Electron Transport systems (tPMETs), and that four mediators cross the plasma membrane to interact with cytoplasmic and mitochondrial redox molecules. Four of the mediators inhibit electron transfer from S. cerevisiae. Catabolic inhibitors were used to locate the cellular source of electrons for three of the mediators.

Simple PCR-based DNA microarray system to identify human pathogenic fungi in skin

Fungal diseases in immunocompromised hosts pose significant threats to their prognoses. An accurate diagnosis and identification of the fungal pathogens causing the infection are critical to determine the proper therapeutic interventions, but these are often not achieved, due to difficulties with isolation and morphological identification. In an effort to ultimately carry out the simultaneous detection of all human pathogenic microbes, we developed a simple system to identify 26 clinically important fungi by using a combination of PCR amplification and DNA microarray assay (designated PCR-DM), in which PCR-amplified DNA from the internal transcribed spacer region of the rRNA gene was hybridized to a DNA microarray fabricated with species-specific probes sets using the Bubble Jet technology. PCR-DM reliably identified all 26 reference strains; hence, we applied it to cases of onychomycosis, taking advantage of the accessibility of tissue from skin. PCR-DM detected fungal DNA and identified pathogens in 92% of 106 microscopy-confirmed onychomycosis specimens. In contrast, culture was successful for only 36 specimens (34%), 3 of which had results inconsistent with the results of PCR-DM, but sequence analysis of the isolates proved that the PCR-DM result was correct. Thus, PCR-DM provides a powerful method to identify pathogenic fungi with high sensitivity and speed directly from tissue specimens, and this concept could be applied to other fungal or nonfungal infectious human diseases in less accessible anatomical sites.

Influência do tempo e do meio de transporte no isolamento de fungos patogênicos de biópsias de pele

FUNDAMENTOS: Não está definido como o meio de transporte e o intervalo de tempo até o processamento final interferem no isolamento de fungos patogênicos em material obtido de biópsias de pele. OBJETIVOS: Determinar o efeito da inoculação tardia de biópsias de pele, transportadas em diferentes meios líquidos, na taxa de isolamento de fungos patogênicos. MÉTODOS: De 47 pacientes com lesões cutâneas suspeitas de micoses invasivas obtiveram-se 278 biópsias das lesões. Cada biópsia foi transportada em frascos com caldo Sabouraud com cloranfenicol ou solução salina de cloreto de sódio e inoculada em ágar Sabouraud após 48-72 horas (precoce) ou após 72 horas até sete dias (tardio), constituindo-se quatro grupos de estudo. RESULTADOS: As medianas das taxas de isolamento dos quatro grupos de esporotricose foram 100% e de paracoccidioidomicose foram 84% e 50% nos grupos precoces/solução salina ou caldo Sabouraud e 64% e 84% nos grupos tardios/solução salina ou caldo Sabouraud, respectivamente (p=0,88). Baixas taxas de contaminação resultaram em especificidade diagnóstica de 82% para doenças não fúngicas. CONCLUSÕES: Biópsias de pele podem ser transportadas em caldo Sabouraud ou solução salina por períodos de até sete dias, à temperatura ambiente, sem afetar a viabilidade dos fungos.

Evaluation of combined deactivators-supplemented agar medium (CDSAM) for recovery of dermatophytes from patients with tinea pedis

Using a newly-developed medium, i.e., combined deactivators-supplemented agar medium (CDSAM), the viability of dermatophytes in skin scales was evaluated. Culture studies were conducted with skin scales collected from 44 patients with tinea pedis who had been treated for two weeks with topical antifungal drugs. Sixty-four percent of the specimens were mycologically positive on CDSAM, while only 23% of these same specimens were positive when cultured on conventional Sabouraud's dextrose agar medium (SDA). Alternatively, 36% of all cases were negative on both media. The experimental data from this clinical study indicate that CDSAM was more useful than SDA in accurately evaluating the efficacy of antifungal drugs since the former minimized the residual effects of drug residues remaining in the skin samples.

Activity of the Triazole Antifungal R126638 as Assessed by Corneofungimetry

BACKGROUND

R126638 is a novel triazole exhibiting potent in vitro and in vivo antifungal activity against fungal pathogens including dermatophytes and yeasts.

OBJECTIVE

To determine the antifungal activity in time in the stratum corneum of healthy volunteers after oral intake of R126638 at a daily dose of 100 or 200 mg for 1 week.

METHOD

Sixteen male volunteers were randomly allocated to oral treatment with either 100 or 200 mg of R126638 once daily for 1 week. Five cyanoacrylate skin surface strippings (CSSS) were obtained from the forearm of each subject before drug intake at day 1. CSSS were also collected during treatment at day 2 (24 h after the first drug intake, before the second drug intake), at day 4 (before the fourth drug intake) and at day 7 (10 h after the last drug intake). The post-treatment lingering effect was assessed at day 10 (3 days after treatment) and at day 14 (7 days after treatment). The corneofungimetry bioassay was performed on these CSSS to assess the antifungal profile of R126638. Cells of different fungal species (Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum canis, Candida albicans and Malassezia globosa) were deposited and cultured for 10 days on CSSS in a sterile and controlled environment. The extent of fungal growth on the stratum corneum was determined using computerized image analysis.

RESULTS

R126638 clearly reduced the growth of all tested fungal species. The onset of effects of R126638 was evidenced at day 4 when it reached statistical significance for 3 of 5 species. At day 7, significance was reached for 4 of 5 species. During the posttreatment period, R126638 remained effective for 4 of 5 species at day 10, and this activity persisted until day 14 for 2 of 5 species.

CONCLUSION

A broad spectrum antifungal activity was rapidly expressed in the stratum corneum after oral intake of R126638. The drug likely reached the upper layers of the stratum corneum by diffusion and persisted in this location for at least 7 days after treatment.

Corneofungimetry Bioassay on Malassezia spp. under Ketoconazole and Desonide Influences

BACKGROUND

Glucocorticoids can boost some Malassezia-driven dermatoses. However, both antifungals and topical corticosteroids improve lesions of seborrheic dermatitis.

OBJECTIVE

To revisit the topical activity of the antifungal ketoconazole and the corticosteroid desonide on Malassezia growth on human stratum corneum.

MATERIAL AND METHODS

The computer-assisted corneofungimetry bioassay was used to compare the growth of M. furfur, M. globosa and M. restricta on human stratum corneum coated with olive oil. Four blinded gel formulations were tested. They contained either 2% ketoconazole, 0.05% desonide or a combination of 2% ketoconazole and 0.05% desonide; one gel was unmedicated. Untreated stratum corneum and specimens coated with a 2% ketoconazole cream were used as negative and positive comparators, respectively. A total of 45 samples (15 M. furfur, 15 M. globosa, and 15 M. restricta) were used for each test formulation in this randomized, double-blind study.

RESULTS

The 2% ketoconazole gel and cream and the combination of 2% ketoconazole and 0.05% desonide formulation abated similarly and significantly the M. furfur, M. globosa and M. restricta growth. The 3 species were similarly sensitive to these formulations. By contrast, no significant inhibitory effect was yielded by the 0.05% desonide gel and the vehicle.

CONCLUSION

The presence of 0.05% desonide does not impair or improve the Malassezia susceptibility to 2% ketoconazole when growing on lipid-enriched human stratum corneum.

Onychomycosis: a critical study of techniques and criteria for confirming the etiologic significance of nondermatophytes

Nondermatophytic filamentous fungi (NDF) other than Scytalidium species are variously said to cause between 0 and 50% of all toenail onychomycoses, though most estimates are in the 2-5% range. Due to the difficulty of obtaining 'gold standard' control data for comparison, the accuracy of many laboratory evaluation processes used to deal with potential NDF onychomycoses has never been rigorously measured, thus allowing use of differing interpretations of the significance of cultures. To allow valid comparison of these procedures and interpretations, a large series of patients who declined treatment were sampled on multiple occasions from all apparently onychomycotic toenails until adequate certainty had been attained that all etiologic agents had been isolated and, where necessary, confirmed as etiologic via consistent repeated isolation. This information was used to evaluate results that had been obtained in the initial direct microscopy and culture studies for the same patient population, as such results are strongly relied on in routine diagnosis. Direct microscopy (KOH) was found to be 73.8% sensitive for dermatophytes and 67.2% sensitive for proven etiologic NDF (difference not significant). Culture of the initial specimen coincidentally had a sensitivity of 74.6% for both fungal groups. KOH and culture in tandem were 83.9% sensitive for indicating fungal etiology based on the first specimen. Different evaluative frameworks currently used to interpret NDF isolations were contrasted. The 'classic' evaluation procedure, in which all NDF considered etiologic must be isolated from at least two successive nail specimens, at least one of which must be microscopic positive for compatible fungal filaments, had a sensitivity of 59.5% but a specificity of 100% for true NDF infections and mixed NDF/dermatophyte infections. The most widely used 'simple association' evaluation criterion, in which NDF outgrowth is considered etiologic whenever direct microscopy is positive for fungal elements and no dermatophyte grows out from the initial specimen, had a sensitivity of 53.6% and a specificity of 70.3% for NDF infections. A frequently criticized, but in some quarters still advocated, variant of the simple association criterion considers NDF outgrowth to be significant whenever the corresponding specimen is positive for fungal filaments in direct microscopy; application of this criterion yielded a sensitivity of 60.7% for true infections but a specificity of only 42%. With the aid of two standard notes soliciting repeat specimens, the classic criterion was able to attain 92.7% accuracy in recognizing all NDF etiologic agents and 100% accuracy in disregarding all contaminants from initial specimens that were positive in direct microscopy and yielded a filamentous fungus in initial culture. Even in exhaustive longitudinal study, only 20.2% of NDF infections were found to be associated with a concurrent dermatophytosis. In auxiliary studies, some nails remained NDF-infected after dermatophytes had been successfully eliminated by therapy.

Itraconazole corneofungimetry bioassay on Malassezia species. Itraconazol-Korneofungimetrie-Bioassay an Malassezia-Arten

Yeasts of the genus Malassezia are part of the normal skin biocenosis and are involved in a series of distinct skin disorders and specific dermatomycoses in man and animals. Several species are currently distinguished. Their relative in vitro susceptibility to antifungals appears different according to the species and to the nature and route of administration of the drug. Corneofungimetry is an ex vivo bioassay allowing to test the fungal response on human stratum corneum following oral intake of a given antifungal by volunteers. Two series of cyanoacrylate skin surface strippings (CSSS) were harvested from the volar forearm of 30 volunteers before and after a 2-week treatment with itraconazole 200 mg daily. They were coated by olive oil and inoculated with suspensions of seven different Malassezia spp. After a 1-week culture on CSSS, the amount of viable yeasts was assessed using neutral red staining assisted by computerized image analysis. Growth of the seven species was not similar on the CSSS from untreated stratum corneum. The ranking order from the most proliferative to the least was M. restricta, M. sympodialis, M. globosa, M. furfur, M. obtusa, M. slooffiae and M. pachydermatis. Their growth was abated to almost the same level after itraconazole treatment. It is concluded that in vivo treatment with itraconazole is highly active against all Malassezia spp. colonizing the human stratum corneum.

Actin gene-targeted RT-PCR could be a useful method for evaluating in vitro fungicidal activity against dermatophytes

This study examined the effects of the antifungal agents amorolfine hydrochloride (AMF) and bifonazole (BFZ) on actin mRNA expression determined by reverse transcription-polymerase chain reaction (RT-PCR) amplification, and the morphology of Trichophyton mentagrophytes. In AMF-treated cultures, the hyphal cells of T. mentagrophytes exhibited concentration- and/or time-dependent progressively degenerative morphological damage. Those cultures exhibiting severe and necrotic morphological changes (such as crushed, bent and flattened hyphal cells) did not express actin mRNA. In BFZ-treated cultures, similar morphological changes were seen in the hyphae of T. mentagrophytes, but these changes were milder than observed in the AMF-treated samples, and actin gene fragments were amplified in all of these samples. These results indicate that actin gene-targeted RT-PCR could be a useful tool for testing the susceptibility of dermatophytes to antifungal agents in vitro.

Onychomycosis: strategies to improve efficacy and reduce recurrence

Fungal infections may be difficult to treat for several reasons. It is important to obtain the correct diagnosis, and select the appropriate antifungal agent and route. General considerations that may be associated with recurrent infections are, a genetic predisposition and suboptimal bioavailability of drug, resulting in insufficient concentration at the target site. The aetiologic organism, the severity of disease, other coexisting diseases, concomitant drug intake, and the presence of fungal infection at other sites are some factors that determine the choice of antifungal therapy and its route of administration, oral vs. topical lacquer. Local factors such as the thickness of the nail, presence of lateral onychomycosis, longitudinal spike, dermatophytoma and severe onycholysis are some factors that may determine the choice of secondary measures such as mechanical or topical treatment. Booster or supplemental therapy may be of benefit when the response to initial treatment is poorer than expected and unlikely to result in complete response. Steps should be taken to reduce the possibility of recurrence once cure has been achieved.

Reverse transcription - 3' rapid amplification of cDNA ends-nested PCR of ACT1 and SAP2 mRNA as a means of detecting viable Candida albicans in an in vitro cutaneous candidiasis model

The presence of viable cells of Candida albicans, in broth or in a reconstructed living skin equivalent, was determined by the detection of amplicons of partial mRNA sequences of the genes encoding fungal actin (ACT1) and secreted aspartyl proteinase 2 (SAP2). The mRNA of both genes were amplified by reverse transcription-3' rapid amplification of cDNA ends-nested polymerase chain reaction. Single bands of ACT1 (315 bp) and SAP2 (162 bp) mRNA were amplified from total RNA extracts of C. albicans grown in yeast carbon base-albumin broth or in living skin equivalent tissue; only the former was amplified from Sabouraud broth-grown organisms. Primer pairs targeted for ACT1 and SAP2 were Candida genus-specific and C. albicans-specific, respectively. The sensitivity limits of the assay were 100 fg of total RNA or 10 cells of C. albicans, by ethidium bromide staining. When C. albicans-infected living skin equivalent was exposed to amorolfine, amplicons of ACT1 and SAP2 mRNA were not detected in total RNA extracts. Non-amplification of the mRNA correlated with the absence of C. albicans growth in Sabouraud agar cultures of living skin equivalent samples. Reverse transcription-3' rapid amplification of cDNA ends-nested polymerase chain reaction of the mRNA encoding specific proteins of an organism has potential application in determining the viability of the organism in tissue, thus monitoring the efficacy of an antimicrobial therapy, and in detecting mRNA expressed in very little amounts in tissue.

Neutral red assay in minimum fungicidal concentrations of antifungal agents

We assayed the fungicidal effects of antifungal agents using neutral red staining. Fungal elements of Trichophyton mentagrophytes and T. rubrum were treated with various concentrations of antifungal agents in 96-well filtration plates and then stained with neutral red. The amount of neutral red incorporated by the surviving viable cells was determined from the automated spectrophotometric readings at 550 nm. The minimum fungicidal concentrations (MFCs) of antifungal agents determined by this assay correlated well with those determined by conventional assay. This newly developed procedure should provide a rapid, reproducible, quantitative, qualitative and semi-automated susceptibility test for determination of the MFCs of the fungicidal agents.

Evaluation of antifungal effects of terbinafine and itraconazole using neutral red staining

Neutral red staining is a newly described method for evaluating the viability of fungal cells. Using this method, the antifungal effects of terbinafine and itraconazole were evaluated in vitro. When the number of neutral red-positive Trichophyton mentagrophytes conidia treated with these two oral antifungals was compared with the number of culture-proved viable T. mentagrophytes conidia, a strong positive correlation was found. This result confirms that neutral red staining is a useful method for evaluating the viability of T. mentagrophytes in vitro, and that it can be used for the evaluation of antifungal activity. We conclude that the effectiveness of an antifungal drug should not be evaluated by direct microscopic examination alone, but with the additional aid of mycological culture or neutral red staining.