Microbiology
Summary
Malassezia furfur is a type of fungus that causes the skin condition known as pityriasis versicolor. This fungus, which is typically part of the normal skin flora, can lead to skin issues under hot, humid conditions. Notably, the fungus is demonstrated to have a "spaghetti and meatball" appearance on a KOH prep of skin scrapings, which is the method for its diagnosis.
Pityriasis versicolor is characterized by hypopigmented or hyperpigmented patches on the skin, especially on the back and chest. The mechanism through which these patches form is the lipid degradation caused by the fungus, leading to the production of acid that damages melanocytes. The fungus generally remains confined to the stratum corneum, the most superficial layer of skin. It's associated with malassezia fungemia in neonates receiving total parenteral nutrition (TPN) as the fungus thrives on lipids and gains access to the body via catheters. Treatment of pityriasis versicolor usually involves the use of topical selenium sulfide, popularly known as Selsun Blue, which promotes the shedding of the stratum corneum where the fungus resides.
Lesson Outline
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FAQs
Malassezia furfur is a yeast-like fungus that is part of the normal skin flora. It can proliferate under hot and humid conditions, leading to several skin conditions including pityriasis versicolor, and other types of cutaneous mycoses.
A suspected infection with Malassezia furfur is typically diagnosed using a KOH prep. This technique involves scraping the skin lightly and examining the sample under a microscope after applying potassium hydroxide (KOH). The KOH dissolves human cells, but leaves the yeast cells intact, making it easier to identify the infection.
Malassezia furfur employs lipid degradation as a part of its metabolic process. This yeast species thrives on the high lipid content found on human skin, particularly in the sebaceous glands. Some subtypes of Malassezia furfur can also produce lipases, enzymes that break down lipids, promoting inflammation and the development of skin conditions.
Several topical agents are effective against Malassezia furfur, including selenium sulfide that is found in Selsun Blue shampoo. Other antifungal therapies such as ketoconazole, clotrimazole, and zinc pyrithione are also widely used. For severe infections, systemic treatment with oral fluconazole or itraconazole may be considered.
Malassezia furfur can contaminate lipid emulsion bags used in total parenteral nutrition (TPN). This contamination can potentially cause systemic infections, particularly in immunocompromised patients receiving TPN. Care must therefore be taken to avoid contamination and monitor patients for signs of systemic infection.
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