SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Fungal diseases

170

ABSTRACT Dermatophytes are a uniquely pathogenic group of fungi that cause most common fungal infections globally. The major cause of athlete’s foot is Trichophyton rubrum, a pathogen of human skin. A recent paper in this journal reported the sequencing and analysis of five additional genome sequences, including that of Trichophyton rubrum. These five join the existing two additional genome sequences to bring the total to seven dermatophyte genome sequences, a notable milestone in the study of these fungi. These additional genomes set the stage for future genome-supported studies on the biology, pathogenicity, and host specificity of this important group of pathogens. To predict how this future might play out, we review the history of Aspergillus genomics since the initial publication of the first three Aspergillus genome sequences in 2005, an event that stimulated important studies of the pathogenic Aspergillus species. From these 7 years of Aspergillus history, we offer some speculation on the future of dermatophyte studies supported by the genome sequences given the similarities, differences, and relative levels of support for studies in these two groups of fungi and the diseases they cause.

Concepts: Gene, Bacteria, Future, Pathogen, Trichophyton rubrum, Onychomycosis, Dermatophyte, Fungal diseases

56

Antimicrobial resistance, a major public health concern, largely arises from excess use of antibiotic and antifungal drugs. Lack of routine diagnostic testing for fungal diseases exacerbates the problem of antimicrobial drug empiricism, both antibiotic and antifungal. In support of this contention, we cite 4 common clinical situations that illustrate this problem: 1) inaccurate diagnosis of fungal sepsis in hospitals and intensive care units, resulting in inappropriate use of broad-spectrum antibacterial drugs in patients with invasive candidiasis; 2) failure to diagnose chronic pulmonary aspergillosis in patients with smear-negative pulmonary tuberculosis; 3) misdiagnosis of fungal asthma, resulting in unnecessary treatment with antibacterial drugs instead of antifungal drugs and missed diagnoses of life-threatening invasive aspergillosis in patients with chronic obstructive pulmonary disease; and 4) overtreatment and undertreatment of Pneumocystis pneumonia in HIV-positive patients. All communities should have access to nonculture fungal diagnostics, which can substantially benefit clinical outcome, antimicrobial stewardship, and control of antimicrobial resistance.

Concepts: AIDS, Medicine, Bacteria, Pneumonia, Diagnosis, Antibiotic resistance, Tuberculosis, Fungal diseases

38

The Pacific Northwest outbreak of cryptococcosis, caused by a near-clonal lineage of the fungal pathogen Cryptococcus gattii, represents the most significant cluster of life-threatening fungal infections in otherwise healthy human hosts currently known. The outbreak lineage has a remarkable ability to grow rapidly within human white blood cells, using a unique ‘division of labour’ mechanism within the pathogen population, where some cells adopt a dormant behaviour to support the growth of neighbouring cells. Here we demonstrate that pathogenic ‘division of labour’ can be triggered over large cellular distances and is mediated through the release of extracellular vesicles by the fungus. Isolated vesicles released by virulent strains are taken up by infected host macrophages and trafficked to the phagosome, where they trigger the rapid intracellular growth of non-outbreak fungal cells that would otherwise be eliminated by the host. Thus, long distance pathogen-to-pathogen communication via extracellular vesicles represents a novel mechanism to control complex virulence phenotypes in Cryptococcus gattii and, potentially, other infectious species.

Concepts: Immune system, White blood cell, Infectious disease, Bacteria, Microbiology, Fungus, Basidiomycota, Fungal diseases

28

In the framework of a survey on dermatophytoses, 14,619 clinical specimens taken from outpatients with symptoms suggestive of tinea and referred to a Medical Mycology laboratory in Tehran, Iran, were analyzed by direct microscopy and culture. In total, 777 dermatophyte strains recovered in culture were randomly identified by a formerly established RFLP analysis method based on the rDNA ITS regions. For confirmation of species identification, 160 isolates representing the likely entire species spectrum were subjected to ITS-sequencing. Infection was confirmed in 5,175 collected samples (35.4%) by direct microscopy and/or culture. Tinea pedis was the most prevalent type of infection (43.4%), followed by tinea unguium (21.3%), tinea cruris (20.7%), tinea corporis (9.4%), tinea manuum (4.2%), tinea capitis (0.8%) and tinea faciei (0.2%). Trichophyton interdigitale was the most common isolate (40.5%) followed by T. rubrum (34.75%), Epidermophyton floccosum (15.6%), Microsporum canis (3.9%), T. tonsurans (3.5 %) and M. gypseum (0.5%). Other species included M. ferrugineum, T. erinacei, T. violaceum, T. schoenleinii, and a very rare species T. eriotrephon (each one 0.25%). The two strains of T. eriotrephon isolated from tinea manuum and tinea faciei are the second and third reported cases worldwide. Application of DNA-based methods is an important aid in monitoring trends in dermatophytosis in the community.

Concepts: Biology, Trichophyton rubrum, Onychomycosis, Dermatophyte, Fungal diseases, Terbinafine, Mycosis-related cutaneous conditions, Dermatophytosis

28

Trichophyton rubrum var. raubitschekii is a rare anthropophilic dermatophyte isolated around the world from tinea corporis, tinea cruris, tinea pedis and tinea unguium. In this study, the isolation rate of T. rubrum var. raubitschekii was studied in 200 cases of tinea pedis and tinea unguium in Japan. The 200 clinical isolates were shown to be of downy type as their colonies on Sabouraud’s dextrose agar were white to cream, suede-like to downy, with a yellow-brown to wine-red reverse, and they produced few macroconidia. The type strain of T. rubrum var. raubitschekii (CBS 100084) and one clinical isolate (KMU 8337; isolated at Kanazawa) of downy type tested positive for urease, but the reference strain of T. rubrum (CBS 392.58) and the remaining 199 clinical isolates tested negative. Further epidemiological investigations are required to study human cases of infection with the granular type of T. rubrum and T. rubrum var. raubitschekii in Japan.

Concepts: Biology, Trichophyton rubrum, Onychomycosis, Athlete's foot, Dermatophyte, Fungal diseases, Terbinafine, Mycosis-related cutaneous conditions

27

Candidemia is one of the most frequent opportunistic mycoses worldwide. Limited epidemiological studies in Latin America indicate that incidence rates are higher in this region than in the Northern Hemisphere. Diagnosis is often made late in the infection, affecting the initiation of antifungal therapy. A more scientific approach, based on specific parameters, for diagnosis and management of candidemia in Latin America is warranted. ‘Recommendations for the diagnosis and management of candidemia’ are a series of manuscripts that have been developed by members of the Latin America Invasive Mycosis Network. They aim to provide a set of best-evidence recommendations, for the diagnosis and management of candidemia. This publication, ‘Recommendations for the management of candidemia in adults in Latin America’, was written to provide guidance to healthcare professionals on the management of adults who have, or who are at risk of, candidemia. Computerized searches of existing literature were performed by PubMed. The data were extensively reviewed and analyzed by members of the group. The group also met on two occasions to pose questions, discuss conflicting views, and deliberate on a series of management recommendations. ‘Recommendations for the management of candidemia in neonates in Latin America’ includes prophylaxis, empirical therapy, therapy for proven candidemia, patient work-up following diagnosis of candidemia, central venous catheter management, and management of complications. This manuscript is the fourth of this series that deals with diagnosis and treatment of invasive candidiasis. Other publications in this series include: ‘Recommendations for the diagnosis of candidemia in Latin America’, ‘Recommendations for the management of candidemia in adults in Latin America’, and ‘Recommendations for the management of candidemia in children in Latin America’.

Concepts: Epidemiology, United States, Catheter, South America, Candidiasis, Fungemia, Fungal diseases, Manuscript

27

Superficial fungal infections due to dermatophytes are common over the world and their frequency is constantly increasing. The aim of our study was to discuss fungal infections with frequency of occurrence, clinical stages and aetiology in patients admitted to dermatological ward and microbiological laboratory of the specialist hospital in Krakow. Investigations performed between 1995 and 2010 included the group of 5333 individuals. Dermatophyte infections, confirmed by culture, were revealed in 1007 subjects (18.9%), i.e. in 553 males and 454 females. The most frequent clinical forms of infections were tinea unguium and tinea pedis, caused mainly by Trichophyton rubrum and by Trichophyton mentagrophytes. Tinea corporis, tinea manuum, tinea capitis and tinea cruris constituted a small percentage of infections and the main aetiological factors of these dermatomycoses were also T. rubrum and T. mentagrophytes. Between 1995 and 2000 there were stated small differences in the number of isolated strains of dermatophytes in comparison with the number of examined patients. Since 2006 there has been observed a decrease in number of patients in our hospital with suspected fungal infections, but per cent of positive cultures has remained unchanged in comparison with earlier period.

Concepts: Trichophyton rubrum, Onychomycosis, Athlete's foot, Dermatophyte, Fungal diseases, Terbinafine, Mycosis-related cutaneous conditions, Dermatophytosis

27

Microsporum canis, for which the natural hosts are cats and dogs, is the most prevalent zoophilic agent causing tinea capitis and tinea corporis in humans. We present here a diagnostic PCR test for M. canis, since its detection and species identification is relevant to the choice of treatment and to the understanding of a probable source of infection. An M. canis-specific PCR was evaluated using 130 clinical isolates of dermatophytes (including M. canis [n = 15] and 13 other species), 10 yeast or mold isolates, 12 hair and skin samples from animals with or without experimental M. canis infection, and 35 patient specimens, including seven specimens positive for M. canis and 15 dermatophyte negative samples. All pure cultures, animal specimens and clinical samples with M. canis were detected by the PCR test, whereas none of the other fungal isolates or samples without M. canis was negative. This study indicates that the PCR test for M. canis identification applied directly to patient specimens or animal hair, as well as to clinical isolates had 100% specificity and sensitivity.

Concepts: Biology, Type I and type II errors, Sensitivity and specificity, Dermatophyte, Fungal diseases

25

Dermatophytosis in individuals with human immunodeficiency virus infection seems to manifest with atypical, multiple, or extensive lesions more frequently. In addition, there are reports of presentations with little inflammation, called anergics. Less common etiologic agents have been isolated in these individuals, such as Microsporum species. To describe clinical aspects and etiologic agents of dermatophytosis in individuals with human immunodeficiency virus (HIV) infection. Patients with clinical diagnosis of dermatophytosis underwent scarification for mycological diagnosis through direct microscopic examination and fungal isolation in culture on Sabouraud dextrose agar. Sixty individuals had a clinical hypothesis of dermatophytosis. In 20 (33.3%) of the 60 patients, dermatophytosis was confirmed through a mycological study. Tinea corporis, diagnosed in 14 patients, was the most frequent clinical form, followed by tinea unguium in 7, tinea cruris in 5, and tinea pedis in 1 patient. Most of the lesions of tinea corporis were anergic. Five patients with tinea unguium had involvement of multiple nails, with onychodystrophy as the predominant subtype. Multiple cutaneous lesions occurred in 3 patients and extensive cutaneous lesions in 4. Regarding the agent, Trichophyton rubrum was the most commonly isolated. The high occurrence of anergic skin lesions and involvement of multiple nails, especially as onychodystrophy, corroborates the hypothesis that atypical, disseminated, and more severe presentations are common in individuals with HIV infection. However, no Microsporum species was isolated even in atypical, extensive, or disseminated cases, in disagreement with previous reports. Therefore, the approach of squamous lesions in HIV-positive patients must include a mycological study, in view of the possibility of anergic dermatophytosis, to promote the introduction of a suitable therapeutic agent.

Concepts: HIV, AIDS, Immune system, Infectious disease, Cytomegalovirus, Onychomycosis, Fungal diseases, Mycosis-related cutaneous conditions

25

Tinea infections are caused by dermatophytes and are classified by the involved site. The most common infections in prepubertal children are tinea corporis and tinea capitis, whereas adolescents and adults are more likely to develop tinea cruris, tinea pedis, and tinea unguium (onychomycosis). The clinical diagnosis can be unreliable because tinea infections have many mimics, which can manifest identical lesions. For example, tinea corporis can be confused with eczema, tinea capitis can be confused with alopecia areata, and onychomycosis can be confused with dystrophic toenails from repeated low-level trauma. Physicians should confirm suspected onychomycosis and tinea capitis with a potassium hydroxide preparation or culture. Tinea corporis, tinea cruris, and tinea pedis generally respond to inexpensive topical agents such as terbinafine cream or butenafine cream, but oral antifungal agents may be indicated for extensive disease, failed topical treatment, immunocompromised patients, or severe moccasin-type tinea pedis. Oral terbinafine is first-line therapy for tinea capitis and onychomycosis because of its tolerability, high cure rate, and low cost. However, kerion should be treated with griseofulvin unless Trichophyton has been documented as the pathogen. Failure to treat kerion promptly can lead to scarring and permanent hair loss.

Concepts: Antifungal drug, Onychomycosis, Athlete's foot, Fungal diseases, Griseofulvin, Terbinafine, Mycosis-related cutaneous conditions, Dermatophytosis