Lipophilic yeastlike organisms associated with tinea versicolor

Cutaneous Malassezia: Commensal, Pathogen, or Protector?

The skin microbial community is a multifunctional ecosystem aiding prevention of infections from transient pathogens, maintenance of host immune homeostasis, and skin health. A better understanding of the complex milieu of microbe-microbe and host-microbe interactions will be required to define the ecosystem's optimal function and enable rational design of microbiome targeted interventions. Malassezia, a fungal genus currently comprising 18 species and numerous functionally distinct strains, are lipid-dependent basidiomycetous yeasts and integral components of the skin microbiome. The high proportion of Malassezia in the skin microbiome makes understanding their role in healthy and diseased skin crucial to development of functional skin health knowledge and understanding of normal, healthy skin homeostasis. Over the last decade, new tools for Malassezia culture, detection, and genetic manipulation have revealed not only the ubiquity of Malassezia on skin but new pathogenic roles in seborrheic dermatitis, psoriasis, Crohn's disease, and pancreatic ductal carcinoma. Application of these tools continues to peel back the layers of Malassezia/skin interactions, including clear examples of pathogenicity, commensalism, and potential protective or beneficial activities creating mutualism. Our increased understanding of host- and microbe-specific interactions should lead to identification of key factors that maintain skin in a state of healthy mutualism or, in turn, initiate pathogenic changes. These approaches are leading toward development of new therapeutic targets and treatment options. This review discusses recent developments that have expanded our understanding of Malassezia's role in the skin microbiome, with a focus on its multiple roles in health and disease as commensal, pathogen, and protector.

Pyocyanin as anti-tyrosinase and anti tinea corporis: A novel treatment study

OBJECTIVE

The aim of this study was to evaluate the efficiency of pyocyanin pigment as a novel compound active against tyrosinase with its depigmentation efficiency for combating Trichophyton rubrum which could be a major causative agent of tinea corporis.

METHODS

Fifty swabs of fungal tinea corporis infections were collected and identified. Five MDRPA isolates were tested for their levels of pyocyanin production. The purified extracted pyocyanin was characterized by UV spectrum and FT-IR analysis. Pyocyanin activity against tyrosinase was determined by dopachrome micro-plate. In addition, the antidermatophytic activity of pyocyanin against T. rubrum was detected by radial growth technique. In vivo novel trial was conducted to evaluate the efficiency and safety of pyocyanin as an alternative natural therapeutic compound against T. rubrum causing tinea corporis.

RESULTS

Purified pyocyanin showed highly significant inhibitory activity against tyrosinase and T. rubrum. In vivo topical treatments with pyocyanin ointment revealed the efficiency of pyocyanin (MIC 2000 μg/ml) to cure tinea corporis compared to fluconazole, which showed a partial curing at a higher concentration (MIC 3500 μg/ml) after two weeks of treatment. In addition, the results revealed complete healing and disappear of hyperpigmentation by testing the safety of pyocyanin ointment and its histopathological efficiency in the skin treatment without any significant toxic effect.

CONCLUSION

Pyocyanin pigment could be a promising anti-tyrosinase and a new active compound against T. rubrum, which could be a major causative agent of tinea corporis. In fact, if pyocyanin secondary metabolite is going to be used in practical medication, it will support the continuous demand of novel antimycotic natural agents against troublesome fungal infections.

Malassezia-Can it be Ignored?

Genus Malassezia comprises of 14 species of “yeast like fungi,” 13 of which are lipophilic and 1 is nonlipophilic. They are known commensals and in predisposed individuals they commonly cause a spectrum of chronic recurrent infections. They rarely also cause serious illnesses like catheter-related blood stream infections, CAPD associated peritonitis etc., Though these fungi have been known to man for over 150 years, their fastidious nature and cumbersome culture and speciation techniques have restricted research. Since the last taxonomic revision, seven new species have been added to this genus. Their ability to evade the host immune system and virulence has increased the spectrum of the diseases caused by them. These agents have been implicated as causal agents in common diseases like atopic dermatitis recently. Though culture-based research is difficult, the new molecular analysis techniques and facilities have increased research in this field such that we can devote more attention to this genus to study in detail, their characteristics and their growing implications implications in the clinical scenario.

Skin diseases associated with Malassezia yeasts: facts and controversies

The implication of the yeast genus Malassezia in skin diseases has been characterized by controversy, since the first description of the fungal nature of pityriasis versicolor in 1846 by Eichstedt. This is underscored by the existence of Malassezia yeasts as commensal but also by their implication in diseases with distinct absence of inflammation despite the heavy fungal load (pityriasis versicolor) or with characteristic inflammation (eg, seborrheic dermatitis, atopic dermatitis, folliculitis, or psoriasis). The description of 14 Malassezia species and subsequent worldwide epidemiologic studies did not reveal pathogenic species but rather disease-associated subtypes within species. Emerging evidence demonstrates that the interaction of Malassezia yeasts with the skin is multifaceted and entails constituents of the fungal wall (melanin, lipid cover), enzymes (lipases, phospholipases), and metabolic products (indoles), as well as the cellular components of the epidermis (keratinocytes, dendritic cells, and melanocytes). Understanding the complexity of their interactions will highlight the controversies on the clinical presentation of Malassezia-associated diseases and unravel the complexity of skin homeostatic mechanisms.

Malassezia yeasts and pityriasis versicolor

PURPOSE OF REVIEW

To analyze the relationships among different Malassezia species and pityriasis versicolor, the only human disease in which the etiologic role of these fungi is fully accepted (although the species implicated remains a matter of discussion).

RECENT FINDINGS

Since 1996, after the taxonomic revision of the genus, a limited number of papers analyzing the role of the different Malassezia species in pityriasis versicolor have been published or were the subject of presentations in congresses; there were only four in the past year. This paper discusses the results of these works, comparing them with results of the authors' most recent study in this field, conducted over the past 16 months.

SUMMARY

Most of the studies published thus far now show that Malassezia globosa is the predominant species found in the lesions of pityriasis versicolor, at least in temperate climates. The authors' recent findings confirm these results. The etiologic role of M. globosa in pityriasis versicolor is based, even more than on its isolation in a high percentage of cultures, on its identification by direct microscopy as typical globose yeast cells producing pseudohyphae in almost 100% of cases. The confirmation of the pathogenic role of this species in pityriasis versicolor could help in understanding these conditions, which are still unclear, which promote its transformation from the saprophytic stage present in healthy skin to the parasitic one, and could also help in selecting the best therapeutic measures.

Recent developments in the immunology and biology ofMalasseziaspecies

Malassezia spp. are members of the normal cutaneous flora, but are also associated with several cutaneous diseases. Recent studies of the interaction of Malassezia spp. with melanocytes, fibroblasts, keratinocytes and dendritic cells have highlighted their potential to modulate the immune response directed against them. In normal skin they may downregulate the inflammatory response, allowing them to live as commensals. In contrast, in atopic/eczema dermatitis syndrome and psoriasis, they may elicit an inflammatory response that contributes to the maintenance of lesions. Future research may define ways to influence this inflammatory cycle and hence to control or prevent exacerbations of these diseases.

Pityriasis versicolor: a review of pharmacological treatment options

Pityriasis versicolor is a common disorder of the skin, which is characterised by scaly hypo- or hyperpigmented lesions on the body. The lipophilic yeast, Malassezia, is considered to be the aetiological agent of this disease. A number of treatment options, both topical and systemic, have been shown to be effective. A critical evaluation of treatment options is presented.

Distribution of Malassezia species in pityriasis versicolor and seborrhoeic dermatitis in Greece. Typing of the major pityriasis versicolor isolate M. globosa

BACKGROUND

The expansion of the genus Malassezia has generated interest in the epidemiological investigation of the distribution of new species in a range of dermatoses, on which variable results have been reported from different geographical regions. No data are thus far available from South-east Europe (Greece).

OBJECTIVES

To study the distribution of Malassezia species in pityriasis versicolor (PV) and seborrhoeic dermatitis (SD) and to investigate whether polymorphisms in the internal transcribed spacer (ITS) 1 region facilitate detection of M. globosa and M. sympodialis subtypes.

METHODS

In total, 109 patients with PV and SD and positive Malassezia cultures were included in the study. Age, gender, primary/recurrent episode, disease extent and clinical form of PV were recorded. ITS 1 polymorphisms of M. globosa and M. sympodialis type and clinical strains were investigated by polymerase chain reaction (PCR)-single-strand conformational polymorphism (SSCP) analysis.

RESULTS

Malassezia globosa was the prevalent species isolated from PV and SD either alone (77% and 39%, respectively) or in combination (13% and 18%, respectively) with other Malassezia species. The pigmented form of PV was strongly correlated with the female gender. PCR-SSCP differentiated five subgroups of M. globosa with one being associated with extensive clinical disease. All M. sympodialis isolates displayed a homogeneous ITS 1 PCR-SSCP profile.

CONCLUSIONS

Malassezia species isolation rates were in agreement with those reported from South-west Europe. PCR-SSCP of the ITS 1 is useful for highlighting prospective clinical implications of M. globosa subtypes.

Allergenic evaluation of Malassezia furfur crude extracts

Crude extracts of the lipophilic yeast Malassezia furfur were obtained from 2, 6, 10 and 28 day old cultures. The in vitro cultivation periods corresponded, respectively, to the lag phase, middle of the log phase, end of log phase and the decline phase of the growth curve, which was based on viable cell counts obtained with a fluorescent viability test. Biochemical analyses showed that the protein and carbohydrate contents were greater in day 10 extracts. Seventy patients with different allergic manifestations and 30 healthy volunteers were skin prick tested using the extracts. Of these, thirteen (18.57%) patients gave positive responses. SDS PAGE gradient electrophoretic profiles of the preparations indicated that the 28 day extracts contained the greatest number of protein bands with molecular weights ranging mostly between 30 and 94 kDa. Immunoblots incubated with individual patient sera showed that four IgE binding M. furfur allergens of approximately 88, 61, 52 and 39 kDa were present in the 28 day extracts. The components identified could be used for detecting IgE mediated responses to M. furfur among individuals affected with different allergic conditions.

The importance of microscopic examination in the management of desquamative diseases of the scalp

After determining the usual malassezic biota of the scalp in adult, normal persons, 259 patients with different desquamative diseases were studied by a simple adhesive tape technique. The main purpose of this study was to investigate the utility of this technique to improve the diagnosis and treatment of patients. Most patients with seborrhoeic dermatitis and sebopsoriasis demonstrated large numbers of Malassezia spp. cells corresponding to the so called "pityrosporosis". Only 43.6% of patients with pityriasis capitis (dandruff) presented with such a diagnosis. Symptomatic pityrosporosis of the scalp should be treated with imidazolic derivatives or other antifungal substances. Patients with psoriasis of the scalp showed a typical microscopic picture represented by parakeratosic (nucleated) keratinocytes with absence of lipophilic yeasts which should be attributed to the usual dryness of the scales Microbial epidermitis (eczema) of the scalp revealed another characteristic picture constituted by abundant leukocytes and bacteria without the presence of yeasts. The different microscopic pictures seen with this simple technique for diseases of the scalp, offer an adjunct to make a proper diagnosis and to establish a convenient treatment in cases which are not clinically well defined.

Atopic dermatitis and fungi

Atopic dermatitis (AD) is a chronic, itching, inflammatory skin disease which is associated with asthma and/or hay fever and a familial occurrence of these conditions. Genetic factors are important in the development of AD, but the exact hereditary pathway is still unknown. Dry skin and the weakened barrier function in patients with AD is very important for the patient's reactions to irritants and other external trigger factors including microorganisms. The standard treatments are topical corticosteroids, topical immunomodulating agents, and emollients. If AD cannot be controlled by this type of treatment, systemic immunomodulating agents may be used. UVB, UVA, or psoralen-UVA may also be used for widespread severe lesions. However, some patients do not respond to these standard treatment, and then it is important to consider the role of microorganisms, house dust mites or food. The role of the Malassezia yeasts in AD, especially AD located to the head and neck region, is now documented in several papers. There are also several papers indicating the role of Candida as an aggravating factor in AD. Patients with AD also develop chronic dermatophyte infections more easily, and patients with AD and chronic dermatophyte infections may show improvement in their AD when treated with antifungal drugs.

Pitiríase Versicolor

A expressão pitiríase versicolor define uma infecção fúngica superficial caracterizada por alterações na pigmentação cutânea. O distúrbio de pigmentação é devido à colonização do estrato córneo por um fungo dimórfico, lipofílico, encontrado na flora normal da pele, conhecido como Malassezia furfur. Trata-se de doença prevalente nos trópicos, mas também comum em climas temperados. Há vários tratamentos disponíveis com taxas elevadas de cura, porém as recorrências são freqüentes.

Malassezia species in skin diseases

Since the taxonomic revision carried out in 1996, enlarging the genus Malassezia to comprise seven different species, a number of studies have investigated from different points of view -- mycological, molecular and immunological -- the relationships of these species with the pathologies associated with lipophilic yeasts, as well as its presence in healthy skin. From these studies, it now appears clear that Malassezia globosa is the main species associated with pityriasis versicolor, which is the only cutaneous disease in which the involvement of Malassezia is undisputed. Nevertheless, this species can also be found in normal skin, in which the predominant species is Malassezia sympodialis. In the remaining dermatological disorders related to Malassezia, the role of these yeasts is controversial. In seborrhoeic dermatitis, atopic dermatitis and folliculitis, several studies have focused on the immunological aspects that could explain the pathogenic mechanism. In other diseases, such as confluent and reticulate papillomatosis, neonatal pustulosis, otitis and onychomycosis, the presence or significance of Malassezia is still a matter of dispute.

Pityriasis versicolor

Pityriasis versicolor is a common superficial fungal infection of the skin. It is caused by Malassezia spp., which are normal human saprophytes. Under certain conditions, both exogenous and endogenous, the fungus can convert from a yeast to a pathogenic mycelial form. This alteration results in mild inflammation of the skin, and in characteristic clinical and histological changes. The taxonomy of Malassezia spp. has recently been modified to include six obligatorily lipophilic species, all of which can be found on human skin, plus one non-obligatorily lipophilic species, which only rarely colonizes human hosts.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should be aware of the role of Malassezia in the development of pityriasis versicolor, the clinical and histological changes arising from this dermatosis, and the diagnosis and treatment of this disorder.

Immunology of diseases associated with Malassezia species

Malassezia species are members of the human cutaneous commensal flora, in addition to causing a wide range of cutaneous and systemic diseases in suitably predisposed individuals. Studies examining cellular and humoral immune responses specific to Malassezia species in patients with Malassezia-associated diseases and healthy controls have generally been unable to define significant differences in their immune response. The use of varied antigenic preparations and strains from different Malassezia classifications may partly be responsible for this, although these problems can now be overcome by using techniques based on recent work defining some important antigens and also a new taxonomy for the genus. The finding that the genus Malassezia is immunomodulatory is important in understanding its ability to cause disease. Stimulation of the reticuloendothelial system and activation of the complement cascade contrasts with its ability to suppress cytokine release and downregulate phagocytic uptake and killing. The lipid-rich layer around the yeast appears to be pivotal in this alteration of phenotype. Defining the nonspecific immune response to Malassezia species and the way in which the organisms modulate it may well be the key to understanding how Malassezia species can exist as both commensals and pathogens.

Humoral immune response to Malassezia furfur in patients with pityriasis versicolor and seborrheic dermatitis

Humoral immune responses against exoantigen components of oval, elliptic and round yeast forms of Malassezia furfur were analysed by ELISA and Western blotting assays, using sera from patients with pityriasis versicolor (PV), seborrheic dermatitis (SD) and healthy adults (HA), as control. Sera from patients with SD showed IgG anti-oval M. furfur titers ranging from 1/400 to 1/6400 showing geometric mean (GM) of 1/1472, higher than those obtained with sera from patients with PV (1/200 to 1/6400, GM = 1/1239). Both patient groups showed mean titres statistically superior (P < 0.05) than those obtained form HA (GM = 1/229). Similar data were also obtained with the elliptic and round antigens. However, the anti-oval IgG mean titers from patients' sera were much higher than those obtained with elliptic or round antigenic components (p < 0.05) Anti-M furfur IgM titers obtained from patient's sera with PV against all three exoantigens were statistically superior (p < 0.05) than HA group. Patients with SD showed IgM titers statistically superior (p < 0.05) only to oval yeasts of M. furfur. The IgA mean titers from patients' groups against the different morphological antigens were shown be slightly higher than those HA group. By Western blot, using rabbit anti-sera, the different antigenic components of M.furfur showed a close relationship mainly between oval and elliptic yeast cells antigens. The 70 kDa component of the M. furfur exoantigen of oval morphology was recognized by 84% of the PV patients' sera. On the other hand, SD patients' sera recognized 3 principal components of 70 kDa (100%), 65 kDa (67%) and 84 kDa (53%). These components may be considered immunological markers for PV and SD. Twenty-five percent of HA sera recognized the components of 65, 70 and 94 kDa. This investigation shows that M. furfur antigens can sensitize the host, mainly the oval yeast form of M. furfur with a very important specific IgG response in patients with SD and PV.

Lipoperoxidase activity of Pityrosporum: characterisation of by-products and possible rôle in pityriasis versicolor

Modification of pigmentation and damage of melanocytes are characteristic features of skin colonisation of Pityrosporum orbiculare hyphae in pityriasis versicolor (PV). The yeast is lipophylic and lipid-dependent, capable of oxidising unsaturated lipid components of skin surface, i.e., unsaturated fatty acids, cholesterol and squalene (SQ). The oxidation of unsaturated fatty acids gives rise to dicarboxylic acids (DA) which behave, in vitro, as competitive inhibitors of tyrosinase. In this work, we further investigate the oxidase activity of Pityrosporum in vitro, by evaluating (a) the generation of lipoperoxides in cultures supplemented with fatty acids at various degrees of unsaturation; (b) the mechanism of SQ oxidation; (c) the chemical characteristics of some by-products of lipoperoxidation; (d) the formation of peroxisomes in fungal cells. In cultures supplemented with the saturated palmitic acid (C16:0) and monounsaturated oleic acid (C18:1 n-9), low amounts of lipoperoxides were detected by a spectrophotometric test, whereas in cultures supplemented with di-unsaturated linoleic acid (C18:2 n-6), significant concentrations were found. Gas chromatography-mass spectrometry analyses showed the generation of linoleic acid hydroperoxides both in Pityrosporum cultures and following incubation of acetone powder of the fungus with the unsaturated fatty acid, indicating the presence of a lipoxygenase activity in the fungus. In cultures supplemented with linoleic acid plus SQ, and increase of lipoperoxide generation was observed and trans-trans farnesal and squalene epoxides have been identified. Electron microscopic examinations have evidenced peroxisomes in cells grown in the presence of linoleic acid, whereas they were not detected in cultures supplemented with oleic acid and palmitic acid. The metabolic activities of peroxisomes, through the formation of hydrogen peroxide and the subsequent generation of hydroxyl radicals, may account for the peroxidation of SQ, which is not a substrate of lipoxygenase. Following these results, we propose a mechanism for DA generation by Pityrosporum metabolism and hypothesize that the lipoperoxidation process induced by lipoxygenase activity of the fungus may be the key to understanding the clinical appearance of skin manifestation of PV.

Skin colonization by Malassezia furfur in healthy children up to 15 years old

The prevalence of M. furfur, a lipodependent fungus, in the skin of 0 to 15-year-old healthy children was studied. Sterilized carpet was used to collect skin samples which were cultured in Oxgall medium (Difco) with 1% olive oil and incubated for 10 days at 37 degrees C M. furfur was recovered in 17.8% of infants, with similar findings in both sexes. The highest prevalence of M. furfur colonization was found among children of 0 to 18 months and 11 to 15-year-olds, with 23.3% and 26.7% respectively.

Adherence of Malassezia isolates to human keratinocytes in vitro--a study of HIV-positive patients with seborrhoeic dermatitis

Adherence of Malassezia yeast cells to human keratinocytes was assessed by a novel technique using double-sided Sellotape. Although adherence using double-sided Sellotape is still merely a model for in vivo adherence, it approximates to the conditions found on the skin surface. There were no differences in adhesive properties to human keratinocytes between Malassezia strains originating from HIV-positive and HIV-negative patients with seborrhoeic dermatitis, nor was there a relationship between the severity of seborrhoeic dermatitis and in vitro adherence to human keratinocytes.

Ketoconazole in atopic dermatitis: therapeutic response is correlated with decrease in serum IgE

The prevalence of specific IgE antibodies to the yeasts Pityrosporum orbiculare and Candida albicans was investigated in adult patients with atopic dermatitis (AD) or with seborrhoeic dermatitis and in healthy controls by means of the radioallergosorbent test (RAST). Of 63 AD patients, 28 (44%) had IgE antibodies to P. orbiculare and 21 (33%) to C. albicans. This is highly significant, since no antibodies were found in sera from other patients or controls. With the intention to treat, 20 patients with AD and a positive RAST to P. orbiculare were given ketoconazole 200 mg daily for 2 months and 200 mg twice weekly for further 3 months. The clinical scores improved during treatment with a reduction in the levels of specific IgE to P. orbiculare and total serum IgE. However, there were no correlations between clinical score and serum levels of P. orbiculare-specific IgE. C. albicans-specific IgE, on the other hand, correlated both with clinical score and with total serum IgE.

Identification of allergen components of the opportunistic yeast Pityrosporum orbiculare by monoclonal antibodies

The yeast Pityrosporum orbiculare (P. orbiculare) is a member of the normal human cutaneous flora, but it is also associated with several clinical manifestations of the skin. We have previously observed IgE-binding components in P. orbiculare extracts, using sera from patients with atopic dermatitis. In the present study, we raised several monoclonal antibodies (MoAbs) against P. orbiculare to characterize some of its antigens, and used Candida albicans (C. albicans) as a control. We obtained several IgG1 MoAbs which specifically recognized P. orbiculare in ELISA. Two of these were selected for immunoblotting studies on P. orbiculare, and two patterns of reactivity emerged. Firstly, one MoAb showed a distinct band at a molecular mass of 67 kDa. In the second pattern, a sharp band at about 37 kDa appeared. In contrast, the IgM antibodies raised reacted with a 14-kDa component; but they reacted with C. albicans in addition to P. orbiculare. The IgG1 antibodies seemed to react with proteins, as their ability to react in ELISA with extract pretreated with protease was greatly reduced. In contrast, IgM MoAbs were much less affected, suggesting that they recognized nonprotein components. To determine whether these MoAbs-binding components were also recognized by human IgE, we adopted a radioimmunoassay (RIA) using the MoAbs as catcher antibodies. Both the 67-kDa and the 37-kDa components were IgE-binding proteins. P. orbiculare RAST positive sera were scored as positive in the RIA, whereas the control serum was not.

Lipase of Malassezia furfur: some properties and their relationship to cell growth

Lipase activity of Malassezia furfur, detected with alpha-naphthyl palmitate as a substrate, appeared to be associated with the insoluble fraction of the organism. Profiles of M. furfur lipase were similar to those of Candida cylindracea lipase. The pH optimum of the lipase was acidic, pH 5.0, which is very similar to skin surface pH. The enzyme activity was strongly activated by a lipase activator, sodium taurocholate (STC). Addition of STC to the culture medium activated cell growth in a dose-dependent manner and induced hyphae production. These results suggest that M. furfur lipase plays an important role in cell growth.

Human infections due to Malassezia spp

The genus Malassezia contains three member species: Malassezia furfur and Malassezia sympodialis, both obligatory lipophilic, skin flora yeasts of humans, and Malassezia pachydermatis, a nonobligatory lipophilic, skin flora yeast of other warm-blooded animals. Several characteristics suggest the basidiomycetous nature of these yeasts, although a perfect stage has not been identified. Classically, these organisms are associated with superficial infections of the skin and associated structures, including pityriasis versicolor and folliculitis. Recently, however, they have been reported as agents of more invasive human diseases including deep-line catheter-associated sepsis. The latter infection occurs in patients, primarily infants, receiving parenteral nutrition (including lipid emulsions) through the catheter. The lipids presumably provide growth factors required for replication of the organisms. It is unclear how deep-line catheters become colonized with Malassezia spp. Skin colonization with M. furfur is common in infants hospitalized in neonatal intensive care units, whereas colonization of newborns hospitalized in well-baby nurseries and of older infants is rarely observed. Catheter colonization, which may occur without overt clinical symptoms, probably occurs secondary to skin colonization, with the organism gaining access either via the catheter insertion site on the skin or through the external catheter hub (connecting port). There is little information on the colonization of hospitalized patients by M. sympodialis or M. pachydermatis. Diagnosis of superficial infections is best made by microscopic examination of skin scrapings following KOH, calcofluor white, or histologic staining. Treatment of these infections involves the use of topical or oral antifungal agents, and it may be prolonged. Diagnosis of Malassezia catheter-associated sepsis requires detection of the organism in whole blood smears or in buffy coat smears of blood drawn through the infected catheter or isolation of the organism from catheter or peripheral blood or the catheter tip. Culture of M. furfur from blood is best achieved with Isolator tubes and plating onto a solid medium supplemented with a lipid source. Appropriate treatment of patients requires removal of the infected catheter with or without temporary stoppage of lipid emulsions; administration of antifungal therapeutic agents does not appear to be necessary. Because many patients who develop Malassezia catheter-associated sepsis have severe underlying illnesses, caution must be exercised in attributing all clinical deterioration to Malassezia infection. Our better understanding of how these organisms cause disease awaits the development of a useful typing scheme for epidemiologic studies and further studies on microbial virulence factors and the role of the immune response in pathogenesis.

Tinea versicolor: histologic and ultrastructural investigation of pigmentary changes

A comparative histopathologic study is made between the hypopigmented and hyperpigmented skin lesions of pityriasis versicolor and normal skin areas utilizing histochemical stains and electron microscopy. There were no differences found between the population of Dopa-positive melanocytes within the hypopigmented and hyperpigmented lesions and the normal skin areas. The total epidermal pigmentation was diminished in hypopigmented lesions. The keratin layer was found to be significantly thicker in hyperpigmented lesions and contained more organisms. In hypopigmented lesions, melanocytes contained fewer and smaller melanosomes and exhibited signs of degenerative cellular changes.

Malassezia furfur colonization of neonates in an intensive care unit

We studied Malassezia furfur colonization of neonates in the neonatal intensive care unit (NICU) and found that the rate was astonishingly high as compared to the previous studies. In very low birth weight (less than 1,000 g) infants we recorded a colonization rate of 80%, and 4% infants with a birth weight greater than 2,000 g. Under 10 day's hospitalization the rate was 11%, and it was 70% after 20 days spent in the unit. Among the infants with the birth weight less than 1,700 g, antibiotic therapy was recorded as a significant risk factor for colonization. In the infants with a greater birth weight, the colonization rate was independent from the risk factors studied. M. furfur colonization could not be linked with occurrence of any symptoms of signs recorded and colonization by M. furfur was so common in NICU that the predictive value of surveillance cultures is poor.

Malassezia pachydermatis isolation from a scarlet macaw

A repeated isolation of Malassezia pachydermatis Weidman from a scarlet macaw is reported. This is the first report of birds infected with this yeast.

A study of pityriasis versicolor in Bangkok (Thailand)

A total of 410 cases of pityriasis versicolor were studied in the Division of Dermatology, Department of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand, during January to December 1987. These comprised 1% of all skin disorders, while infection caused by fungus comprised 17%. Most persons infected with pityriasis versicolor were 12-21 years old (mean age 20 years) and 47% were male and 53% were female. The common sites of infection were back, arms, face and trunk. The colors of lesions found were white (83%), brown (7%), pink (6%) and ashy (4%). Both forms of M. furfur were isolated, the ovale form in 97% and the orbiculare form in 3% of cases. The colors of the lesions did not depend on the form of the organism. Mycological and immunological studies confirmed that the two forms were different stages in the complex developmental cycle of a single species.

Vaccines for the management of dermatophyte and superficial yeast infections

Efforts have been made to induce protective immunity to the infections caused by dermatophytes, Candida, and Malassezia. The following conclusions can be drawn from the studies reviewed. 1. The research directed toward the management of dermatophyte infections by vaccination have yielded a promising vaccine for prevention of T. verrucosum infections in cattle. 2. A number of investigators have attempted, by various methods and with different immunogenic preparations, to prevent superficial mucocutaneous candidiasis. The results of those investigations do not indicate that a vaccine for prophylaxis of this disease is forthcoming. 3. No vaccination attempts for prevention of pityriasis versicolor have been described.

Activity of triazole derivatives against Pityrosporum orbiculare in vitro and in vivo

The in vitro antimycotic activity and the in vivo antimycotic activity (in a rabbit model) of itraconazole against P. orbiculare were compared to the corresponding activities of ketoconazole. Fluconazole's in vitro antimycotic activity and in vivo antimycotic activity against P. orbiculare were tested in the same models. The MIC values of itraconazole against P. orbiculare were 0.1-0.2 micrograms/ml compared to 0.02-0.05 micrograms/ml for ketoconazole. For fluconazole, the MIC values were 12.5-50.0 micrograms/ml against P. orbiculare. In a rabbit model, orally administered itraconazole (5 mg/kg) afforded protection against experimental pityriasis (tinea) versicolor in four out of five rabbits. Ketoconazole (1 mg/kg) was effective in all four animals. The in vivo results with fluconazole were in contrast to its low in vitro activity. Fluconazole (5 mg/kg) afforded protection against experimental pityriasis (tinea) versicolor in five out of six animals.

[Pityriasis versicolor due to Malassezia ovalis]

In a randomly collected series of 175 cases of pityriasis versicolor in residents of the central-northern part of Venezuela, 13% of the patients were infected with ovoid unicellular units of the causal fungus (Malassezia ovalis) and 87% with globous unicellular units in the scales (M. furfur). Only globous unicellular units (Pityrosporum orbiculare) were seen outside the active lesions and in these, after the successful treatment with ketoconazole. The median age of 40 'ovalis' patients was 37.5 years; the same in 40 'furfur' patients was 24.5 years. The median age at the moment of discovering the first lesions among 'ovalis' patients was 31; among 'furfur' patients this was 20 years. There were 16 male patients among the 'ovalis' and 24 among the 'furfur' groups of 40. The topographic distribution of the lesions varied according to the type of the invader. M. ovalis prevailed on the trunk below the waist-line and on the limbs, mainly on buttocks and upper legs. M. furfur prevailed on the chest, neck, face and upper limbs. The hypothesis is offered that the ovoid agent of pityriasis versicolor preferentially occupies the less sweating and sebum-producing parts of the body in older (and drier) persons than the globous type does.

The Pityrosporon yeasts. Their role as pathogens

P. orbiculare (P. ovale), a member of the normal human cutaneous flora, is also an opportunistic pathogen, and the association with tinea versicolor is well-documented. Recently, the Pityrosporon yeasts have been associated with several other diseases. That Pityrosporon folliculitis is a separate disease is now documented. The association with CRP and with some cases of psoriasis and seborrheic dermatitis seem probable but are not yet fully proven. Reports show that P. orbiculare (P. ovale) are involved not only in dermatologic diseases, again indicating that the organisms are not "harmless" saprophytes. Because of our awareness of this association, more cases of systemic infections with Pityrosporon yeasts may be reported.

Quantitative culture of Pityrosporon orbiculare

The author describes for the first time a method to culture Pityrosporon orbiculare quantitatively. Different nonionic detergents were studied for their in vitro effect to minimize aggregation of P. orbiculare. Triton X-100 0.1% had only a slight inhibitory effect when the organism was held less than 2 hours. A critical point in quantitative culturing of P. orbiculare seems to be the medium. With this medium, solitary colonies and optimal growth are achieved. No statistically significant differences were found in quantitative cultures from lesions and normal skin in patients with tinea versicolor, but this was observed when quantitative cultures from lesions and normal skin in patients with tinea versicolor were compared with healthy controls.

Adherence of Pityrosporum orbiculare to human stratum corneum cells

This investigation demonstrates the capacity of Pityrosporum orbiculare to adhere to human stratum corneum cells in vitro; this may be an important initial step in its colonization of stratum corneum. Adherence was significantly higher when incubation for 120 min (mean 9.4 adherent yeasts) was compared to 60 min (mean 3.5 adherent yeasts, P less than 0.001), but not to 90 min (mean 8.6 adherent yeasts, P greater than 0.05). Adherence was higher at an incubation temperature of 37 degrees C (mean 10.0 adherent yeasts) as compared with 25 degrees C (mean 4.0, P less than 0.001), but not at 32 degrees C (mean 8.0, P greater than 0.1). There was no significant difference in adherence related to the anatomic area (forearm, back, and chest) from which the stratum corneum cells have been collected. No difference was seen in adherence between different Pityrosporum strains, but it increased significantly with inoculum size of P. orbiculare, being optimal at 10(7) cells ml-1. The adherence of P. orbiculare and Staphylococcus epidermidis to stratum corneum cells was not influenced by incubation of the organisms together or alone. This model opens possibilities to study the influence of: stratum corneum cells from diseased skin compared with controls; antibodies; and types of surface receptors and antimycotics on P. orbiculare adherence to stratum corneum cells.

Antigenic similarities and differences in genus Pityrosporum

Using the indirect immunofluorescence technique no differences were observed in intensity of staining when antisera against Pityrosporum orbiculare and P. ovale or IgG fractions of these were incubated with P. orbiculare and P. ovale cells. However, a weaker reaction was observed with these antisera and P. pachydermatis cells. With IgG fractions the nonspecific fluorescence was minimized. Fungal cells in biopsies from tinea versicolor lesions showed a brilliant staining with the IgG fractions of antisera against P. orbiculare. This investigation indicates a close antigenic relationship between all of the 3 Pityrosporum species. A common antigenicity was found between P. orbiculare and P. ovale cells as well as between P. orbiculare cells from culture and the fungal cells in biopsies from tinea versicolor lesions. This strongly suggests that these 2 species are identical with each other and with the organism found in tissue.

Experimental infections in rabbits and humans with Pityrosporum orbiculare and P. ovale

The purpose of this investigation was to produce experimental tinea versicolor in rabbits and humans with Pityrosporum orbiculare and P. ovale. P. orbiculare and P. ovale were inoculated, with and without occlusion, on the inside of the ear in 10 male rabbits and on the upper arm in 10 patients with a history of tinea versicolor, and in 3 healthy volunteers. After 1 week tinea versicolor-like lesions were produced with both P. orbiculare and P. ovale in 8 of 10 rabbits. Likewise experimental infections, similar to those found clinically in tinea versicolor, were seen, after 1 week, in 5 patients with a history of tinea versicolor and in the 3 healthy volunteers. Two of 5 patients inoculated for only 4 days showed identical but less pronounced lesions. Experimental infections could only be produced with occlusion. Microscopically short hyphae and transformation between round and oval forms were seen in both P. orbiculare and P. ovale. This investigation adds to the identity of P. orbiculare and P. ovale and also to the identity of these 2 fungi and the fungus seen in tinea versicolor. Spontaneous healing and the fact that experimental infections were produced only under occlusion illustrates the importance of predisposing factors in tinea versicolor.