Dermatophyties diagnostiquées au laboratoire de parasitologie et mycologie de l’hôpital Le Dantec de Dakar, entre 2007 et 2011

Development, preparation, and evaluation of a novel non-adjuvanted polyvalent dermatophytes vaccine

Ringworm is a worldwide distributed contagious disease infecting both man and animals that constitute an economic, zoonotic, and health problem concern all over the world. During the last decade, attention has been directed to vaccination as an ideal approach to the control of such diseases. In the present study, non-adjuvanted polyvalent vaccines were prepared from locally isolated hot and virulent dermatophyte species, namely Trichophyton verrucosum (T. verrucosum), Trichophyton mentagrophytes (T. mentagrophytes), and Microsporum canis (M. canis) were immunologically evaluated. The prepared vaccine evaluation was focused on the aspects of immunogenicity and protective efficacy using guinea pigs. Both in its living or inactivated forms, the vaccine-induced significant humoral and cell-mediated immune responses and achieve proper protection of guinea pigs against challenging infections with homologous and heterologous dermatophyte strains. On the other hand, investigations on dermatophyte exo-keratinases showed that it was better produced and more expressed in a mineral-based medium containing pure keratin (3 g/L) than in the same medium with human hair supplementation (2.6 g/L). The maximum dermatophyte productivity of exo-keratinases was found to be between 18 and 21 days post-incubation. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two fractions with molecular weights of 40 kDa (fraction I) and 28 kDa (fraction II) have been identified in the culture filtrate of the three involved dermatophyte species. Both fractions demonstrated keratinolytic activity. The specific activity of the isolated keratinases (number of Keratinase units (KU)/mg protein) was stronger in fraction I, where it reached 18.75, 15.38, and 14 KU/mg protein as compared to 12.9, 8.74, and 12 KU/mg protein in fraction II of T. verrucosum, T. mentagrophytes, and M. canis, respectively. The dermatophyte exo-keratinases proved to be immunogenic as they stimulated high keratinase-specific antibody titers and induced strong delayed skin hypersensitivity reactions in vaccinated animals. Anti-keratinase-specific IgG was detected in sera of guinea pigs immunized with the inactivated or living polyvalent dermatophyte vaccines by a homemade enzyme-linked immunosorbent assay (ELISA) using dermatophyte exo-keratinases as coating antigen. The intradermal injection of dermatophyte exo-keratinases induced specific delayed skin reactions in guinea pigs immunized with the inactivated or the living polyvalent dermatophyte vaccines. The intradermal injection of dermatophyte exo-keratinases in the control non-sensitized guinea pigs was associated with itching, swelling, and bloody scar formation, however, no skin indurations were formed. The development of those post-exo-keratinases injection reactions in the control non-sensitized apparently healthy guinea pigs group, suggests an exo-keratinases possible role in the pathogenesis of dermatophytosis.

Evaluation of the Multiplex Real-Time PCR DermaGenius® Assay for the Detection of Dermatophytes in Hair Samples from Senegal

For the successful treatment of dermatophytoses, especially tinea capitis, there is a need for accurate and rapid diagnostic methods. A lot of recent literature has focused on the detection of dermatophytes directly on sample material such as nails, hair and skin scrapings. Molecular tools offer the ability to rapidly diagnose dermatophytosis within 48 h. This study aimed to compare the results of a commercial real-time PCR (real-time PCR) assay DermaGenius^®(DG) 2.0 complete multiplex kit with those of conventional diagnostic methods (direct microscopy and culture). A total of 129 hair samples were collected in Dakar (Senegal) from patients suspected of dermatophytosis. DG was applied for the molecular detection of Candida albicans, Trichophyton rubrum/soudanense, T. interdigitale, T. tonsurans, T. mentagrophytes, T. violaceum, Microsporum canis, M. audouinii, Epidermophyton floccosum, T. benhamiae and T. verrucosum. Dermatophytes species and C. albicans were differentiated by melting curve analysis. The sensitivity and specificity of the PCR assay were 89.3% and 75.3%, respectively. DG PCR was significantly more sensitive than culture (p < 0.001). DG PCR is fast and robust to contamination. In this paper, the main questions discussed were the replacement of culture by a broad-spectrum fungal real-time PCR and the implementation of DG PCR into a routine laboratory in Senegal.

Real-Time PCR Assay for the Detection of Dermatophytes: Comparison between an In-House Method and a Commercial Kit for the Diagnosis of Dermatophytoses in Patients from Dakar, Senegal

Background. PCR assays have been developed for the diagnosis of dermatophytes, yet data in African populations are scarce. Objective. This study aimed to compare two PCR assays for the diagnosis of dermatophytosis in outpatients at the Aristide Le Dantec University Hospital in Dakar, Senegal. Patients and methods. A total of 105 samples, including 24 skin, 19 nail and 62 hair samples collected from 99 patients were included in this study. Each sample was subjected to conventional diagnosis (CD), including direct microscopy and culture, and two real-time PCR assays: one in-house (IH)-PCR, used at the University Hospital of Marseille and the Eurobio Scientific commercial kit (CK): designed for the specific detection of six dermatophytes not including Microsporum audouinii. Results. Of the 105 specimens, 24.8%, 36.2% and 20% were positive by CD, IH-PCR and CK-PCR, respectively. The IH-PCR and CK-PCR exhibited 88.9% and 65.4% sensitivity, respectively. With a 36.6 diagnostic odd ratio and 1.41 needed to diagnose, the IH-PCR displayed better diagnostic indices than the CK-PCR. It is notable that, when considering the species that it claims to detect, when it came to skin and nail samples, CK-PCR sensitivity increased to 77%. Conclusions. The pan-dermatophyte IH-PCR performed better in the diagnosis of dermatophytosis in this African population than the CK-PCR, which is not designed to detect M. audouinii. Nevertheless, both assays exhibited similarly good diagnostic indices for tinea corporis and tinea unguium, both of which are localisations where M. audouinii is more rarely involved than in tinea capitis.

Epidemiological aspects of superficial fungal infections in Koranic schools in two localities of Senegal (Thies and Touba)

BACKGROUND

In developing countries, superficial fungal infections (SFI) are endemic and cause a therapeutic problem because of the duration and cost of treatment. Community living and promiscuity are key factors in the direct or indirect transmission and spread of these diseases.

OBJECTIVES

The objective was to study the epidemiological aspects of SFI, among koranic school children in two localities in Senegal.

PATIENTS/METHODS

School koranic students were recruited in Thies and Touba. Diagnosis of fungal diseases was carried out using conventional techniques (microscopic examination and culture).

RESULTS

Among 210 children, the overall prevalence of SFI was 25.71%, with 27.63% in Touba and 20.68% in Thiès. The clinical lesions were epidermophytosis (0.5%), intertrigo (0.9%), palmoplantar keratoderma (KPP) (0.9%), onychomycosis (7.7%) and tinea capitis (TC) (90%). The species responsible for the SFI were Trichophyton soudanense (85.18%), Microsporum audouinii langeronii (9.25%), Trichophyton rubrum (3.70%) and Chrysosporium keratinophilum (1.85%). The prevalence of infection was higher among boys (85.18%).

CONCLUSION

Superficial fungal infections are prevalent in koranic school children and attention should be given to non-dermatophytic species that could be responsible for SFI.

A Comparative Study on Phenotypic versus ITS-Based Molecular Identification of Dermatophytes Isolated in Dakar, Senegal

Classically, dermatophytes are identified by phenotypic methods even if these methods, sometimes, remain difficult or uncertain. On the other hand, nucleotide sequence analysis of internal transcribed spacers (ITS) of rDNA has proved to be a useful method for identification of dermatophytes. The objective of this study was to compare the phenotypic method with DNA sequencing of the ITS regions for identification of dermatophyte species isolated in Dakar, Senegal. A collection of thirty-two strains of dermatophytes were isolated from patients suffering from dermatophytosis. Mycological identification revealed Trichophyton soudanense (n = 13), T. interdigitale (n = 10), Microsporum audouinii (n = 5), and one strain for each of the following species: T. rubrum, T. mentagrophytes, and M. canis and one unidentified strain. For comparison, ITS-based PCR and DNA sequencing were applied for identification of the isolated dermatophytes. ITS sequences showed, in BLAST search analysis, 99-100% of similarity. Identification of dermatophyte isolates by conventional methods was confirmed by DNA sequencing of the ITS regions in 84% of cases. Discrepancies concern mostly T. rubrum misidentified as T. interdigitale. PCR sequencing provided an excellent tool for identifying dermatophyte strains that do not present typical morphological characteristics. It was also able to give correct identification of an atypical strain of M. audouinii responsible of mycetoma of the scalp.

[Causative agents of superficial mycoses isolated in Dakar, Senegal: Retrospective study from 2011 to 2015]

INTRODUCTION

Superficial fungal infections, particularly of the skin, scalp and nails are very common and have been reported worldwide. The most common causative agents of these mycoses are dermatophytes, yeasts and molds. However, these agents vary with time and depend on many factors including the geography. The objective of this study was to identify the causative agents of superficial mycoses diagnosed at the Le Dantec University Hospital in Dakar (Senegal).

MATERIAL AND METHODS

The study concerned 1851 outpatients received in the parasitological and mycological laboratory of Le Dantec hospital during the period from January 2011 to December 2015. Every patient benefited from direct examination and mycological culture.

RESULTS

Among the 1851 patients, 633 were confirmed with superficial mycoses and the prevalence was 34.2 %. The age of patients ranged from two months to 81 years with a mean age of 31 years. Superficial mycoses were found more in women (70.3 %) than men (29.7 %) and a little more than thirty-nine percent (39.3 %) were adults. The causative agents identified were: dermatophytes (58 %), yeast (36.7 %) and non-dermatophytic filamentous fungi (NDFF, 5.3 %). The most isolated species were: Candida albicans (26.9 %), Trichophyton soudanense (24.9 %) and T. rubrum (13.7 %). These fungi were responsible for different clinical aspects, isolated and other associated. Among the isolated clinical aspects, those affecting hair (tinea capitis) were by far the largest with 44.8 %, followed by tinea unguium (34.5 %). Associations were especially type of tinea capitis and tinea manuum (2.4 %) and toenails onychomycosis associated with interdigital tinea pedis (2.7 %). Tinea capitis agents were exclusively dermatophytes and the predominant agent was T. soudanense with 47,8 %. Tinea unguium agents were yeast (79 %), dermatophytes (18 %) or NDFF (3 %) and the most found species was C. albicans (63.9 %). Dermatophytes, yeasts and molds were respectively found more in children and young adults, older adults and young adults and older adults and the elderly.

CONCLUSION

In definitive, these epidemiological data should enable better diagnostic and therapeutic management of superficial mycoses.

[Nondermatophytic and noncandidal fungi isolated in Le Dantec University hospital of Dakar in 2014: Epidemiological, clinical and mycological study]

In recent years, the incidence of superficial fungal infections involving nondermatophytic and noncandidal fungi increased considerably. The objective of this work was to analyze the epidemiological, clinical and mycological fungal infections due to nondermatophytic and noncandidal fungi diagnosed in the laboratory of parasitology-mycology of Le Dantec hospital in Dakar. With a retrospective study of the various cases of nondermatophytic and noncandidal fungi isolated in the laboratory of parasitology-mycology during the period of November 2013 to December 2014, we collected 22 cases of infections in 11 men and 11 women; age ranging from 17 to 75 years with a mean of 45.3 years (sex ratio=1): eight cases of intertrigo, seven cases of onychomycosis, four cases of palmoplantar keratoderma (KPP), a case of onychomycosis associated with interdigital intertrigo, a case of infectious myositis and one case of African histoplasmosis. We have isolated and identified a total of 22 nondermatophytic and noncandidal fungi: ten Fusarium, five Trichosporon, two Chrysosporium, two Geotrichum, one Rhodotorula, one Neoscytalidium dimidiatum and one Histoplasma capsulatum var. duboisii. So we are seeing the emergence of nondermatophytic and noncandidal increasingly isolated from superficial and local lesions. These fungi, generally contaminants or commensal, cause a problem regarding their direct involvement in pathological processes in which they are isolated. So we should respect the recommendations proposed for their involvement in pathological processes and, by a collaboration between clinician and biologist, demonstrate their real involvement through effective, targeted treatment.