Comparison of diagnostic methods in the diagnosis of dermatomycoses and onychomycoses

Loop-mediated isothermal amplification-microfluidic chip for the detection of Trichophyton infection

Trichophyton is the most pathogenic type of fungal skin infection. It often invades and grows in a keratin-rich matrix, and lesions include human skin, hair, and fingernails (toenails). We designed LAMP primers for Trichophyton and developed a LAMP-Microfluidic chip detection system for Trichophyton. This system detects six common species of Trichophyton in the genus Trichophyton, including Trichophyton rubrum, Trichophyton mentagrophyte, Trichophyton violaceum, Trichophyton tonsurans, Trichophyton verrucosum, and Trichophyton schoenleinii. The specificity reached 100%, and the sensitivity could reach about 1 × 10² copies/μl. The entire detection process can be completed within 60 min and does not cross-react with other dermatophytes. The established LAMP-Microfluidic chip detection system has the advantages of simple operation, high specificity, and high sensitivity, and has the potential for clinical application.

Mixed Cutaneous Infection Caused by Leishmania and Dermatophytes: A Rare Coincidence or Immunological Fact

Leishmaniasis was first described in 1824, in the Jessore district of Bengal (now Bangladesh) and more prevalent in Bihar, Uttar Pradesh, Jharkhand, and West Bengal. The disease is associated with depressed cellular immunity. Tinea is a fungal infection of the skin, which can become more extensively pathogenic particularly in patients with depressed cell-mediated immunity. Regulatory T cells and Th17 cells have been shown to be responsible for post-kala-azar dermal leishmaniasis (PKDL). We present a rare case of a 52-year-old house wife with a history of recurrent itching, depigmentation of the skin of extremities, and loss of appetite for 2-3 months followed by progressive spread of such lesion all over the body in an apparently healthy female. On examination, there were many hypopigmented scaly lesions mainly over the extensor aspect of the body. Skin lesions were characteristics of tinea infection with or without PKDL. A diagnosis of PKDL with tinea was made based on the history of kala-azar and on the skin slit smear for amastigote forms, rK39 test, and KOH mount. Routine blood investigations showed negative serology for HIV and lower normal CD4+T counts. The patient was advised for treatment on systemic antifungal therapy with antihistaminics and later with miltefosine. We have highlighted that PKDL, although uncommon, is a distinct manifestation of VL. In our case study, we also tried to find the reason of coinfection; this was probably due to the depressed cellular immunity, skin abruptions, and acquired dermatophytic infection which is prevalent and associated with lower CD4+ T cell count.

Trichoscopic signs of tinea capitis: a guide for selection of appropriate antifungal

BACKGROUND

Tinea capitis is the most common pediatric dermatophyte infection. Optimal treatment regimen differs according to the type of the dermatophyte involved.

OBJECTIVES

The aim of this work was to study the trichoscopic signs in relation to isolated organism in a sample of Egyptian patients with tinea capitis and the possibility of using them as a guide for selection of appropriate antifungal.

METHODS

This study was carried out on 60 subjects with tinea capitis. Patients were mycologically examined, both direct microscopy with KOH preparation and culture of the scraped hair materials on Sabouraud dextrose agar. Culture mounts were used for identification of the organism. Trichoscopic examination of all patients was performed using the Dermlite DLIII dermoscope.

RESULTS

There was significant higher prevalence of both comma and corkscrew hair in endothrix infection and T. violaceum-infected cases. On the other hand, there was significant higher prevalence of zigzag, barcode hairs, and white sheaths in ectothrix infection and M. canis-infected cases.

CONCLUSION

While some trichoscopic findings are nonspecific, others were found to be more specific. Finding zigzag hairs and barcode hairs points to ectothrix infection (M. canis), and it is recommended to start treatment with griseofulvin. On the other hand, finding comma hairs and corkscrew hairs without zigzag hairs and barcode hairs points to endothrix infection (T. violaceum), and it is recommended to start treatment with terbinafine in the usual dose.

Epidemiological Characteristics and Risk Factors of Tinea Pedis Disease Among Adults Attending Tikrit Teaching Hospital/ Iraq

BACKGROUND

Tinea pedis is one of the most common skin infections of interdigital toe webspace as well as feet skin and may affect the nail or the hand. It is caused by dermophytes fungi especially Trichophyton species. Direct contact with a contaminated environment or animal is the main mode of transmission. Tinea pedis is more frequent among adults than children and more among those with the previous infection with the disease, diabetes mellites, abnormally increased sweating, and the disease is common among individuals who wear unventilated (occlusive) footwear. Tinea pedis is 2-4 times more common in men than females.

AIM OF THE STUDY

To study the epidemiological characteristics and risk factors of tinea pedis disease.

METHODS

Descriptive study was conducted on patients attending the dermatology outpatient clinic in Tikrit Teaching Hospital, Tikrit, Iraq. The study was done during the period from 1st November 2018-10th June 2019. The sample included 680 persons. The cases were diagnosed clinically and by a direct microscope. The demographic information of patients was obtained according to certain questionnaire design. The study was done to reveal the epidemiology of tenia pedis disease among affected patients.

RESULTS

The frequency of tinea pedis cases among the study sample was 7% (48/ 680). It has been observed that there was no significant association as a result of the difference in gender, body weight, positive family history, history, presence of fungal skin disease, and presence of nail trauma. On the contrary, a significant association was observed as a result of the presence of the young age group, diabetes mellitus, and history of wearing occlusive shoes.

CONCLUSION

The frequency of tinea pedis disease among the study sample was 7%. There was a significant association between age group and the presence of diabetes mellitus disease and wearing occlusive shoes.

[Relevance of biopsies for the diagnostics of infectious skin diseases]

Pathogen-related skin infections are a common problem in the dermatological practice. Apart from culturing and serological detection methods, a skin biopsy is a possible diagnostic procedure, especially when the clinical picture is unspecific and other non-infectious skin diseases are considered as possible differential diagnoses. Some organisms can already be detected by routine staining methods (hematoxylin & eosin, e. g., yeasts, Leishmania), for others numerous histochemical and immunohistochemical stains are available, e. g. periodic acid-Schiff reaction (PAS) and Grocott for hyphae and spores, Ziehl-Neelson and Fite-Faraco for Mycobacteria or specific antibodies for Treponema pallidum or herpesviruses. In other instances, an infectious disease may not be diagnosed with certainty in a histological section but the pattern of inflammatory infiltrates is highly suggestive of an infectious cause. Based on such reaction patterns, the dermatopathologist can advise the clinician to perform cultures or serological investigations or additional molecular biological techniques can be applied to the biopsy specimen in order to identify the pathogens. This article presents skin infections with their histopathological features and highlights diseases that can be diagnosed with certainty in a biopsy and those in which a biopsy is helpful to exclude differential diagnoses or to perform molecular diagnostics on the specimen.

Mycological profile of tinea capitis in schoolchildren in rural southern Ethiopia

Tinea capitis is a known common infection among schoolchildren in developing countries that is still underreported in Ethiopia. The aim of this study was to examine the epidemiologic and etiologic profile of tinea capitis among school-aged children in a rural area in southern Ethiopia. We collected demographic and clinicodermatological data from school children aged 3-12 years with tinea infections. Pathologic specimens were taken for potassium hydroxide (KOH) mount and mycological culture. Dermatophyte species were identified by macroscopic examination of the colony and microscopic examination of fungal cultures. A total of 634 schoolchildren were screened in the study; 128 cases were suspected for tinea capitis based on clinical examination of which 99 patients (mean age 6.7 years within a range of 4-12 years), who were subsequently positive, either based on KOH examination or showed growth of dermatophytes on culture, were included in our study. The ratio of males to females was 3:1. A total of 88 patients (89.9%) had a culture positive for dermatophytes. The zoophilic species Trichophyton verrucosum was the most prevalent isolate (n = 29 cases), followed by the anthropophilic species T. tonsurans (n = 27). The other Trichophyton species implicated were T. mentagrophytes (n = 14), as well as T. schoenleinii, T. soudanense, and T. violaceum. Only 11 of the isolates belonged to the genus Microsporum: M. audouinii (n = 8), M. ferrugineum (n = 2), and M. gallinae (n = 1). T. verrucosum, followed by T. tonsurans were the most frequent causative agents in this study.

Bedside diagnostics in dermatology: Viral, bacterial, and fungal infections

Viral, bacterial, and fungal infections are frequently encountered in clinical practice, resulting in numerous cutaneous manifestations. Although diagnosis of these infections has changed over time because of technological advancements, such as polymerase chain reaction, bedside diagnostic techniques still play an important role in diagnosis and management, enabling rapid and low-cost diagnosis and implementation of appropriate therapies. This 2-part article will review both common and infrequent uses of bedside diagnostic techniques that dermatologists can incorporate into daily practice. This article examines the utility of bedside tests for the diagnosis of viral, bacterial, and fungal infections. The second article in this series reviews the use of bedside diagnostics for parasitic and noninfectious disorders.

Reappraisal of Conventional Diagnosis for Dermatophytes

Dermatophytoses include a wide variety of diseases involving glabrous skin, nails and hair. These superficial infections are a common cause of consultation in dermatology. In many cases, their diagnosis is not clinically obvious, and mycological analysis therefore is required. Direct microscopic examination of the samples using clearing agents provides a quick response to the clinician and is usually combined with cultures on specific media, which must be used to overcome the growth of contaminating moulds that may hamper the recovery of dermatophytes. Accurate identification of the causative agent (i.e. at the species level), currently based on morphological criteria, is necessary not only to initiate an appropriate treatment but also for setting prophylactic measures. However, conventional methods often lack sensitivity and species identification may require up to 4 weeks if subcultures are needed. Histological analysis, which is considered the "gold standard" for the diagnosis of onychomycoses, is seldom performed, and as direct examination, it does not allow precise identification of the pathogen. Nevertheless, a particular attention to the quality of clinical specimens is warranted. Moreover, the sensitivity of direct examination may be greatly enhanced by the use of fluorochromes such as calcofluor white. Likewise, sensitivity of the cultures could be enhanced by the use of culture media containing antifungal deactivators. With the generalization of molecular identification by gene sequencing or MALDI-TOF mass spectrometry, the contribution of historical biochemical or physiological tests to species identification of atypical isolates is now limited. Nevertheless, despite the recent availability of several PCR-based kits and an extensive literature on molecular methods allowing the detection of fungal DNA or both detection and direct identification of the main dermatophyte species, the biological diagnosis of dermatophytosis in 2016 still relies on both direct examination and cultures of appropriate clinical specimens.

Rapid diagnosis of tinea incognito using handheld reflectance confocal microscopy: a paradigm shift in dermatology?

Dermatophytoses are common skin infections. Traditional diagnostic tests such as skin scrapings for light microscopy examination, fungal cultures and biopsies remain imperfect due to false-negative test results, cost, time required to perform the procedure, time delays in test results and/or a requirement for an invasive procedure. Herein, we present a case of an 80-year-old female whose tinea incognito was non-invasively diagnosed within seconds using handheld reflectance confocal microscopy (RCM). As non-invasive skin imaging continues to improve, we expect light-based office microscopy to be replaced with technologies such as RCM, which has multiple and continually expanding diagnostic applications.

Comparison of modified Chicago sky blue stain and potassium hydroxide mount for the diagnosis of dermatomycoses and onychomycoses

The diagnostic value of modified Chicago sky blue (CSB) stain and potassium hydroxide (KOH) mount for superficial mycoses was compared using fungal culture as gold standard. The sensitivity and screening time of the CSB stain were superior to the KOH mount. The CBS stain is simple, quick and reliable for diagnosing superficial mycoses.

[Biological diagnosis of onychomycoses. Direct examination after simplified technique of PAS staining]

Confirmation of fungal origin of onychopathy by mycological examination is essential. For that purpose, in parallel to the cultivation of biological samples, achieving a sensitive and informative direct examination of nail fragments and subungual material is primordial. Among the direct examination techniques, and inspired from a technique of reference in histo-pathology (the "periodic acid-Schiff reagent" reaction), the simplified technique of PAS staining according to Hotchkiss and MacManus is the technique of choice. Easy to implement and very sensitive, it can immediately and formally confirm the diagnosis of onychomycosis, mention the type of fungus (yeast, dermatophyte, Hyphomycete opportunistic) and suspect a possible multiple involvement.

Comparison of diagnostic methods in the evaluation of onychomycosis

Onychomycosis is a common nail problem, accounting for up to half of all nail diseases. Several nail disorders may mimic the onychomycosis clinically. Therefore, a sensitive, quick, and inexpensive test is essential for screening nail specimens for the administration of the proper drug. The aim of this study was to compare 4 different diagnostic methods in the evaluation of onychomycosis and to determine their sensitivity, specificity, positive predictive value, and negative predictive value. In a cross-sectional study, nail specimens were collected from 101 patients suspected to have onychomycosis during a 14-month period. The nail specimens were examined using potassium hydroxide (KOH) 20 %, KOH-treated nail clipping stained with periodic acid-Schiff (KONCPA), and calcofluor white (CFW) stain, and grew a fungal culture. The culture was chosen as the gold standard for statistical analysis using the McNemar and chi-square tests. Out of 101 patients, 100 (99 %) patients had at least 1 of the 4 diagnostic methods positive for the presence of organisms. The positive rates for the fungal culture, KOH preparation, CFW, and KONCPA were 74.2, 85.1, 91.09, and 99.01 %, respectively. The sensitivity and negative predictive value of KONCPA was 100 %. KONCPA was the most sensitive among the tests and was also superior to other methods in its negative predictive value. KONCPA was easy to perform, rapid, and gave significantly higher rates of detection of onychomycosis compared to the standard methods of KOH preparation and fungal culture. Therefore, KONCPA should be the single method of choice for the evaluation of onychomycosis.

Concordance between direct microscopy and fungical culture for the diagnostic of feet's onychomycosis

Prospective study compared the agreement between the direct microscopy and fungical culture from subungueal samples of the patients with clinical suspicion of feet's onychomycosis. The agreement occurred in 56.1% of the exams with dermatophytes, in 52.4% by others fungi and in 90.4% of the negative cases, 0,54 according to the Kappa`s test. In 39.3% of the onychomycosis caused by dermatophytes and 31.8% by nondermatophytes, these were identificated only for direct microscopy. The direct microscopic showed more sensibility compared with the culture, being superior in 19.5% of the total sample and maintaining agreement with the culture in 71.5% of the sample.

Diagnostic procedures in dermatology

Although most skin diseases can be diagnosed with simple visual inspection, laboratory investigations are necessary in several clinical circumstances. This contribution highlights the usefulness of routine diagnostic procedures that are often overlooked and the innovative methods of molecular biology, which are expensive and require an experienced staff. Among the classic diagnostic investigations are (1) the use of Wood's light in many dermatologic disorders (eg, vitiligo, pityriasis versicolor, erythrasma, porphyrias), (2) cytodiagnosis of Tzanck in dermatologic practice (eg, herpetic infections, molluscum contagiosum, leishmaniasis, pemphigus vulgaris, basal cell carcinoma, erythroplasia of Queyrat, Hailey-Hailey disease), and (3) microscopic examination for fungal and bacterial skin infections as well as for mite infestation using potassium hydroxide, simple saline, and Gram stain. Modern molecular biotechnologies encompassing gene-specific polymerase chain reaction and its variants have a substantial affect in selected cases of viral (especially herpes simplex virus), bacterial, fungal, and protozoan (Leishmania) skin infections.

Management of tinea capitis in childhood

Tinea capitis (TC) is a common dermatophyte infection affecting primarily prepubertal children. The causative pathogens belong to only two genera: Trichophyton and Microsporum. Although there is a great local variation in the epidemiology of TC worldwide, T. tonsurans is currently the most common cause of TC with M. canis second. Even though there is an emerging number of anthropophilic scalp infections, M. canis remains the predominant causative organism in many countries of the Mediterranean basin, the most important dermatophyte carriers being stray cats and dogs as well as pet puppies, kittens and rabbits. TC always requires systemic treatment because topical antifungal agents do not penetrate down to the deepest part of the hair follicle. Since the late 1950s, griseofulvin has been the gold standard for systemic therapy of TC. It is active against dermatophytes and has a long-term safety profile. The main disadvantage of griseofulvin is the long duration of treatment required which may lead to reduced compliance. The newer oral antifungal agents including terbinafine, itraconazole, ketokonazole, and fluconazole appear to have efficacy rates and potential adverse effects similar to those of griseofulvin in children with TC caused by Trichophyton species, while requiring a much shorter duration of treatment. They may, however, be more expensive.

Conventional methods for the diagnosis of dermatophytosis

Dermatophytes are keratinolytic fungi responsible for a large variety of diseases that can affect glabrous skin, nails and hair. In many cases, the diagnosis is not clinically obvious, and mycological analysis is required. This includes both direct microscopic examination and cultures. First of all, clinical specimens have to be sampled according to localization and characteristics of the lesions. Direct microscopic examination is usually performed using clearing reagents (KOH or Amman's chloral-lactophenol), but its sensitivity may be greatly enhanced by the use of stains or fluorochromes such as Congo red or Calcofluor white. Histological analysis is an efficient method, but it is constraining for the patients and, as direct examination, it does not allow precise identification of the pathogen. Cultures are therefore needed, and specific culture media may be used to overcome the growth of rapidly growing contaminating moulds which may hamper the recovery of dermatophytes. Identification at the species level which may be useful to initiate an appropriate treatment or for setting prophylactic measures, relies on macroscopic and microscopic morphology. Subcultures on culture media which stimulate conidiation and, for some species, the production of pigments, are often necessary. Additionally, in case of atypical isolates, some biochemical or physiological tests may be performed such as the search for urease activity or the in vitro hair perforation test. However, their contribution to species identification is rather limited, and progress is still needed for the development of biochemical or immunological tests allowing an accurate identification at the species level, pending for the availability of molecular biology-based kits.