This blog was written by Maryam Almatruk a master's student in the Department of Biological Sciences at Western Illinois University
The most common species of Malassezia are:
Malassezia furfur : can cause opportunistic infections in humans and animals and some species cause hypopigmentation in humans (11).
Malassezia dermatis: can cause opportunistic infections in animals (12).
Malassezia pachydermatis : In special conditions, it can cause opportunistic infections and cause skin and ear infections (11).
Geographic distribution of the fungus:
Look Alikes:
Macroscopic Features:
Diagnostic description: There are unique characteristics of some Malassezia species such as Malassezia furfur. It is a unicellular yeast that can also produce conidia with phialides (An open-ended, flask-like conidiophore) and collarettes (a hyphal that connect two cells in the mycelium) (10). Phialides and collarettes give conidia bowling pin appearance. Moreover, on Wood's lamp examination, the clinical lesions have a yellow fluorescence (8).
Malassezia in medical mycology:
Clinical cases (human pathogen):
Figure 4: Pityriasis versicolor shows the flat and minimally scaly in the back.
Figure 10: The crusty, grainy, or scaly appearance at the base of the eyelashes
Treatment
History:
The history of the Malassezia yeasts and their role in human infections was a debate topic in the medical field because of the conflicts on yeast nomenclature. Malassezia was previously classified as Microsporum furfur and Pityrosporum malassez (1). The most common species of Malassezia are:
Malassezia furfur : can cause opportunistic infections in humans and animals and some species cause hypopigmentation in humans (11).
Malassezia dermatis: can cause opportunistic infections in animals (12).
Malassezia pachydermatis : In special conditions, it can cause opportunistic infections and cause skin and ear infections (11).
Malassezia sympodialis : can cause opportunistic infections in animals such as atopic eczema (13).
Identification and Habitat:
Malassezia yeasts are within the Basidiomycota phylum. It is a monophyletic, dimorphic, and lipophilic fungus. Malassezia occurs as a member of the microbial flora of the skin in humans (more common in adults) (4). Furthermore, individual species of the fungus have specific host preferences. The yeast is more common in the face, scalp, chest, back because of sebaceous glands density in these parts. It can also colonize the external ear and the hair follicles. It can be found on the skin of birds and domestic animals and can caused dermatitis in dogs and cats. It can also cause otitis externa in pigs (8).
Geographic distribution of the fungus:
It can be found in tropical and subtropical forest (4). For instance, M. furfur and M. sympodialis are commonly found in Japan. M.globosa has been reported in Spain and M. globosa is commonly seen in UK (6).
Look Alikes:
In immunocompromised transplant patients, Malassezia furfur can be confused with Candida folliculitis because it can cause a distinctive folliculitis (7). However, Malassezia furfur can be distinguished from Candida and other Malassezia species. Malassezia furfur requires oil and fatty acids for growth. Also, it has the appearance of spaghetti and meatballs hypha on the tissue (8).
Macroscopic Features:
Malassezia sp. can take a week to grow at 25 °C, but it can grow rapidly at 30-37°C. Malassezia colonies are raised and smooth with creamy yellow to brown color or orange-beige, and get dry and wrinkled as they age (9).
http://www.mycology.adelaide.edu.au/Mycoses/Superficial/Malassezia_infections/
Figure 1: Culture of M. furfur on Dixon's agar.
Microscopic Features:
The shape of Malassezia cells is globose to ellipsoidal with round and blunt end. Malassezia produce conidia, and there is no sexual spores. Malassezia is a dimorphic fungus. This means that can present a hyphal form and as yeast. In vitro, Malassezia found as a spherical yeast form (5 micrometers). However, it can have different shapes depend on the site of infections. For example, the spherical form on the trunk and the oval form on the scalp (9). The hyphal form is short, septate hyphae (2 – 3 micrometers wide), but it is rarely produced in culture (8).
Figure 2: 10% KOH with Parker ink mount showing characteristic spherical yeast cells and short pseudohyphal elements typical of the fungus.
Chemicals features
Malassezia could not be grown in vitro for a long time until it was discovered that Malassezia require lipids to grow (5). Malassezia is able to grow in Sabouraud's dextrose agar (SDA), malt agar, whole-fat cow's milk, or Modified Dixon agar. However, chloramphenicol, cycloheximide, and a sterile olive oil need to be added to have the ideal media for the lipophilic fungus to grow (5).
Diagnostic description:
Malassezia in medical mycology:
Malassezia is considered in medical mycology because it can cause superficial infections. However, in certain conditions Malassezia can cause opportunistic systemic infections in humans (5).
Clinical cases (human pathogen):
The most common clinical cases caused by Malassezia sp. are: pityriasis versicolor, pityriases folliculitis, seborrheic dermatitis, catheter-celated fungemia in neonates, atopic dermatitis, acne vulgaris dacrocystitis, seborrheic blepharitis psoriasis, and onchyomycosis confluent and reticulated papillomatosis (11).
1. Pityriasis Versicolor (Tinea Versicolor):
Definition:
It is a chronic (stay very long time on skin), superficial skin infection caused by M. globosa and M. sympodialis. It can exist in healthy and immunocompromised people. However, the infections are more common in young adults when sebaceous gland activity is in its maximum (6).
It is a chronic (stay very long time on skin), superficial skin infection caused by M. globosa and M. sympodialis. It can exist in healthy and immunocompromised people. However, the infections are more common in young adults when sebaceous gland activity is in its maximum (6).
Site of infection:
Symptoms:
The skin is rash usually discolored to reddish brown by exposure to sun (12).
Treatment:
Pyrithione zinc shampoo
Antifungal cream or lotion, such as ketoconazole, econazole, oxiconazole, or ciclopirox.
Antifungal pills, such as ketoconazole, fluconazole, or itraconazole (12).
http://www.skinsight.com/child/tineaVersicolor.htm
Figure 3: Pityriasis versicolor showing white spots in the neck and neck.
Figure 4: Pityriasis versicolor shows the flat and minimally scaly in the back.
2. Pityriases Folliculitis
Definition:
The infection is more common in tropical climates when it hot and with humid weather. It is usually appear after sun exposure (12).
Site of infection:
The most commonly affected parts are hair follicles (12). However, the infections can be in the back, chest and upper arms, and sometimes the neck (14).
Symptoms:
Hair follicles become inflamed with red bumps after sun exposure when UV rays are strong because it irritates follicles (12). It also characterized by having follicular papules and pustules localized on the skin (14).
http://www.buzzle.com/articles/folliculitis-treatment.html
Figure 5: The small red bumps around the follicles are characteristic of the infection
Treatment:
Imidazole is used in mild cases, and casesketoconazole or itraconazole in more serious cases (14).
3. Seborrheic Dermatitis ) dandruff)
Definition:
The infection can be a chronic condition. It is common in infants and patients with neurological disease (12).
Symptoms and Site of infection:
Site of infection: The infections appear as white-yellowish scales on or near oily areas of skin, such as the scalp, and inner ear (12).
http://www.dermnet.com/images/seborrheic-dermatitis
Figure 6: white-yellowish scales on the scalp common characteristic of the infection
http://www.dermnet.com/images/seborrheic-dermatitis
Figure 7: white-yellowish scales on the inner ear
4. Atopic Dermatitis
Definition: it is an allergic skin disorder.
Symptoms and Site of infection:
Itchy and dry skin. Also, rashes and skin lesions in the face, behind the knees, on the hands and feet and inside the folds of the elbows. The lesions are red, and swollen.
The infection is inflamed skin with blisters over crusts that stay for a long time. In some cases the infections can be ear discharge or bleeding (6).
http://hardinmd.lib.uiowa.edu/dermnet/dermatitisatopic4.html
Figure 8: rashes and skin lesions in the feet
5. Acne Vulgaris Dacrocystitis ) acne(
Site of infections:
The infection appears as clogging of follicles in the skin, inflammation of the lacrimal sac, and in the inner ear.
Symptoms:
The most common symptoms are redness, discharge, whiteheads, blackheads, pimples, and pustules (6).
http://lookfordiagnosis.com/mesh_info.php?term=dacryocystitis&lang=1
Figure 9: red whiteheads around the eye
6. Seborrheic Blepharitis Psoriasis
Definition:
It is a chronic inflammation and irritation of the skin (eye eyelid). The source of infection can be genetic or caused by the fungus. It most common in people (15-35 age) with a weak immune system.
Symptoms:
The infections appear as a red skin with yellow flaky scales, burning, sensitivity, irritation, and blurred vision (6).
Epidemiology and pathogenesis:
The infections are more common in adults and teenagers than children due to activity of sebaceous glands. There are some conditions that caused having massive growth of the fungus, such as warmer season, excessive sweating, bad diet, pregnant state, oral contraceptives antibiotics or immunosuppressive conditions (e.g. AIDS) (12).
Examples of case studies:
Case 1:
A 2-year-old boy had erythematous patches on the left cheek with coarse scaling and a circumscribed border. He had been treated with corticosteroids but the condition was worst (15).
Figure 11: Erythematous patches on the left cheek
Diagnosis:
Microscopic examination showed fungal hyphae together with round yeast cells. The scales were inoculated into a special medium (include adding olive oil) and incubated at 30 C for 4 days. The growth was creamy and wrinkled, direct microscopic examination showed globular yeast cells which is the characteristics of Malassezia (15).
Figure 12: short, wide, fungal hyphae with round yeast cells
Treatment:
The patient was cured by local application of ketoconazole (15)
Case 2:
A 40-year-old man had light erythematous scaly patch on the shoulder and back, with slight lichenification and a sharp border. The lesion had the appearance of neurodermatitis (15).
A 40-year-old man had light erythematous scaly patch on the shoulder and back, with slight lichenification and a sharp border. The lesion had the appearance of neurodermatitis (15).
Figure 13: Light erythematous scaly patch on the shoulder
A direct microscopic examination showed short, wide hyphae. The scales were inoculated as describe in case 1. The growth was creamy and wrinkled, direct microscopic examination showed globular yeast cells which is the characteristics of Malassezia (15).
Figure 14: A large amount of short, wide hyphae was found in scales.
The patient was cured after 2 weeks by using ketoconazole cream (15).
Literature cited
1. Gaitanis G, et all. 2012. The Malassezia Genus in Skin and Systemic Diseases. doi: http://cmr.asm.org/content/25/1/106.full
2. Gaitanis G, et all. 2012. The Malassezia Genus in Skin and Systemic Diseases. doi: http://cmr.asm.org/content/25/1/106.full
4. Saunders C, Scheynius A, Heitman J. 2012. Malassezia Fungi Are Specialized to Live on Skin and Associated with Dandruff, Eczema, and Other Skin Diseases.doi: http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1002701
5. Inamadar A, Palit A. 2003. The genus Malassezia and human disease. doi: Inamadar A, Palit A. 2003. The genus Malassezia and human disease. doi: http://www.ijdvl.com/article.asp?issn=0378 6323;year=2003;volume=69;issue=4;spage=265;epage=270;aulast=Inamadar
6. Lileas M & Gupta N. 2011. Malassezia Infections. doi: http://people.ysu.edu/~crcooper01/Malassezia-x11.pdf
7. Sandin RL , et all. 1993. Malassezia furfur folliculitis in cancer patients. The need for interaction of microbiologist, surgical pathologist, and clinician in facilitating identification by the clinical microbiology laboratory. doi: http://www.ncbi.nlm.nih.gov/pubmed/8239485
8. Volk T, Heiking S.n.d. Malassezia furfur & madash: Pityriasis (tinea) versicolor infection agent. doi: http://eol.org/pages/248533/details
9. Buxton R. 2011. Microscopic Examinations of Skin Infections–Yeast. doi: http://www.microbelibrary.org/library/fungi/2874-microscopic-examinations-of-skin-infections-yeast
10. REFERENCES & GLOSSARY. n.d.doi: http://wildpro.twycrosszoo.org/S/00Ref/KeywordsContents/C/Collarette.htm
11. Inamadar A, Palit A. 2003. The genus Malassezia and human disease. doi: Inamadar A, Palit A. 2003. The genus Malassezia and human disease. doi: http://www.ijdvl.com/article.asp?issn=0378 6323;year=2003;volume=69;issue=4;spage=265;epage=270;aulast=Inamadar
12. Sugita T, et all. 2012. New Yeast Species, Malassezia dermatis, Isolated from Patients with Atopic Dermatitis. doi: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC140359/
13. Harsha B, et all. 2011. Granulomatous Dermatitis due to Malassezia sympodialis. doi: http://www.archivesofpathology.org/doi/full/10.5858/2010-0588-CRR.1
14. Bolognia, Jean L., 2003. Tinea Versicolor A parent's guide to condition and treatment information doi: http://www.skinsight.com/child/tineaVersicolor.htm
15. Zhao Y. at all, 2010. Cutaneous malasseziasis: four case reports of atypical dermatitis and onychomycosis caused by Malassezia.doi: http://onlinelibrary.wiley.com/doi/10.1111/j.1365- 4632.2009.04178.x/pdf
