The Fungi
Julius P. Kreier in Infection, Resistance, and Immunity, 2022
Fungi exist in nature mainly as saprophytes. Only about fifty of over 200 thousand known species of fungi have been identified as pathogens of humans and animals. Fungal diseases have been classified according to the tissues and organs affected and the range of clinical manifestations. The superficial mycoses are those conditions which Involve the superficial layers of the dermis. The most common agents involved in these diseases are the dermatophytes. The skin is well protected against colonization by dermatophytes by its function as a physical barrier, its low moisture content, and the presence of normal bacterial flora which compete for iron and may also secrete antifungal chemicals. The agent Sporothrix schenkii is a common soil saprophyte. It is found in higher concentrations in environments enriched with spaghnum moss or other organic matter. Sporothrix is a dimorphic fungus, which grows as mycelia in the environment but grows as a yeast in the host.
Aetiology and Laboratory Diagnosis
Raimo E Suhonen, Rodney P R Dawber, David H Ellis in Fungal Infections of the Skin, Hair and Nails, 2020
Dermatophytosis of the scalp, glabrous skin and nails is caused by a closely related group of fungi known as dermatophytes which have the ability to utilise keratin as a nutrient source, i.e. they have a unique enzymatic capacity. It is important to stress that fewer than 50% of dystrophic nails are of fungal aetiology and that it is therefore essential to establish a correct laboratory diagnosis by microscopy and/or culture before treating a patient with a systemic antifungal agent. For a laboratory diagnosis, clinicians should be aware of the need to generate an adequate amount of suitable clinical material. In patients with suspected dermatophytosis of the nails, the nail plate should be pared and scraped using a blunt scalpel until the crumbling white degenerating portion is reached. Therefore, it is essential to perform both direct microscopy and culture on all specimens, and repeat collections should always be considered in cases of suspected dermatophytosis with negative laboratory reports.
Skin infections
Ronald Marks, Richard Motley in Common Skin Diseases, 2019
The stratum corneum is an excellent barrier to pathogenic microorganisms, but is itself sometimes the target of attack. The skin surface and its adnexal structures harbour a stable microflora, which lives in symbiosis with skin and may indeed be beneficial. Gram-positive cocci, Gram-positive lipophilic microaerophilic rods and a Gram-positive yeast-like organism live in the follicular lumina without normally causing much in the way of harm. Dermatophyte infections are restricted to the stratum corneum, the hair and the nails. Pityriasis versicolor disorder is caused by the yeast-like microorganism Pityrosporum ovale . This microaerophilic, lipophilic denizen of the normal follicle only occasionally becomes pathogenic when its growth is encouraged by heightened rates of sebum secretion or there is depressed immunity. Trichophyton, Microsporum and Epidermophyton species are responsible for this group of dermatophyte infections. Microsporum canis caught from dogs, cats or other children causes tinea capitis in children and, uncommonly, other types of ringworm infection.
Development of a new synthetic xerogel nanoparticles of silver and zinc oxide against causative agents of dermatophytoses
Published in Journal of Dermatological Treatment, 2019
Ali Abdul Hussein S. Al-Janabi, Abass M. Bashi
Background: Dermatophytes, which are the common causative agents of superficial infection on the human skin called dermatophytosis that can be treated by various antifungal drugs. Nanoparticles composed of such drugs have many benefits. A new form called xerogel of silver nanoparticles (Ag-NPs) and zinc oxide nanoparticles (ZnO-NPs) was prepared and tested against dermatophytes. Methods: Xerogel consists of Ag-NPs and ZnO-NPs was prepared. Characteristics of chemical composition, surface morphology, and nanoparticle size were determined. Antidermatophytic action of prepared xerogel was investigated against Trichophyton mentagrophytes and Trichophyton verrucosum. Results: The new preparation exhibited satisfactory character of xerogel nanoparticles. Trichophyton mentagrophytes showed more susceptibility to xerogel with lower minimum inhibitory concentration than T. verrucosum. Conclusions: Xerogel nanoparticles composed of Ag and ZnO were successfully prepared. They had antidermatophytic action in specific concentrations.
Emerging therapies for the treatment of ungual onychomycosis
Published in Drug Development and Industrial Pharmacy, 2015
Avadhesh Kushwaha, Reena N. Murthy, S. Narasimha Murthy, Rania Elkeeb, X. Hui, Howard I. Maibach
Introduction: Onychomycosis, a common fungal infection in the finger and toe nails, affects approximately 2–8% of the worldwide population. Fungal infection is more complicated in those who suffer from conditions, such as diabetes, peripheral vascular diseases and compromised immune diseases. Area covered: Onychomycosis treatment has been classified on the basis of location of infection in the toes and fingers and infectious agents (dermatophytes fungi, yeast and non-dermatophyte molds). In this review, the available therapies (traditional and device based) and their limitations for the treatment of onychomycosis have been discussed. Expert opinion: The success rate with topical nail products has been minimal. The main reason for this poor success rate could be attributed to the lack of complete understanding of the pathophysiology of the disease and clinical pharmacokinetic data of drugs in the infected nail apparatus.
Emerging drugs for the treatment of onychomycosis
Published in Expert Opinion on Emerging Drugs, 2019
Introduction: Onychomycosis is a widespread nail disease, often occurring on the feet. It is a chronic and often recurring disease, which makes it difficult to eradicate. The infection may be caused by dermatophytes, non-dermatophyte molds, and yeasts. Traditionally, systemic antifungal medications have been used to treat this infection, but in recent years topical formulations have been the focus of research. Areas covered: This review outlines the current antifungal market and novel treatments currently in development or in experimental phases. It highlights a shift from systemic treatments to topical options as well as penetration enhancers. There are also several novel systemic options in development. Expert opinion: Although there have been significant developments in treatment options for onychomycosis, it remains a challenging chronic condition with less than desirable cure rates. This may be attributed to the formation of fungal biofilms and limited understanding of the fungal lifecycle. However, when patients adhere to treatment protocols and employ preventative measures, outcomes are generally favorable.
Related Knowledge Centers
- Epidermis
- Keratin
- Virulence
- Ringworm
- Onychomycosis
- Ascomycota
- Onygenales