Monitoring spread of Malassezia infections in a neonatal intensive care unit by PCR-mediated genetic typing

Molecular differentiation of seven Malassezia species

A system based on PCR and restriction endonuclease analysis was developed to distinguish the seven currently recognized Malassezia species. Seventy-eight strains, including authentic culture collection strains and routine clinical isolates, were investigated for variation in the ribosomal DNA repeat units. Two genomic regions, namely, the large subunit of the ribosomal gene and the internal transcribed spacer (ITS) region, were amplified by PCR, and products were digested with restriction endonucleases. The patterns generated were useful in identification of five out of seven Malassezia species. M. sympodialis was readily distinguishable in that its ITS region yielded a 700-bp amplified fragment, whereas the other six species yielded an 800-bp fragment. M. globosa and M. restricta were very similar in the regions studied and could be distinguished only by performing a hot start-touchdown PCR on primers for the beta-tubulin gene. Primers based on the conserved areas of the Candida cylindracea lipase gene, which were used in an attempt to amplify Malassezia lipases, yielded an amplification product after annealing at 55 degrees C only with M. pachydermatis. This specific amplification may facilitate the rapid identification of this organism.

Otitis externa associated with Malassezia sympodialis in two cats

The lipid-dependent species Malassezia sympodialis was isolated from two cats with otitis externa. To our knowledge, this is the first report of the isolation of lipid-dependent species of the genus Malassezia associated with skin disease in domestic animals.

Characterization of Malassezia species by means of phenotypic characteristics and detection of electrophoretic karyotypes by pulsed-field gel electrophoresis (PFGE)

A total of 220 isolates of the genus Malassezia obtained from affected skin of animals and humans were included in this study. The isolates were examined for their belonging to the known species Malassezia pachydermatis, Malassezia sympodialis, Malassezia furfur, Malassezia obtusa, Malassezia restricta, Malassezia globosa and Malassezia slooffiae by means of phenotypic and biochemical characteristics as well as their ability to assimilate polyethylen(20)-sorbitan-esters (Tween 20, 40, 60, 80). The electrophoretic karyotypes of all isolates were studied by pulsed-field gel electrophoresis. Of the 220 Malassezia isolates examined, 217 were identified as M. pachydermatis and three were classified as M. sympodialis. Moreover, the proof of limited lipid-dependence of M. pachydermatis indicated that the commonly used criterion 'lipid-independence' is not sufficient to differentiate this species from the other known Malassezia species.

Malassezia pachydermatis: a review

Malassezia pachydermatis is of importance in both veterinary and human medicine. Its taxonomic status and physiological characteristics are now better understood. Skin disease associated with this lipophilic yeast is now commonly recognized, especially in dogs. However, further studies are required to elucidate the mechanisms which allow this yeast to proliferate and induce disease. Skin colonization is common in pet carnivores which consequently constitute a source of M. pachydermatis for susceptible humans. In the future, the development of efficient typing systems should allow better understanding of the transmission mechanisms.

Isolation of Malassezia furfur from a cat

During a survey of the occurrence of Malassezia species in the external ear canals of cats without otitis externa, Malassezia furfur was isolated. This is the first report of the isolation of M. furfur from cats.

Molecular typing of Malassezia species with PFGE and RAPD

The currently recognized seven species of Malassezia all have different karyotypes which do not vary intraspecifically, except in M. furfur which displayed two different karyotypes. In contrast, random amplified polymorphic DNA (RAPD) typing showed the presence of genetic variation in all species. It is concluded that karyotype analysis is useful for species identification, and RAPD typing can be used in epidemiological investigations.

Epidemiological analysis of Malassezia pachydermatis isolates by partial sequencing of the large subunit ribosomal RNA

The opportunistic yeast Malassezia pachydermatis is commonly recovered from both normal and diseased skin of warm-blooded animals. The diversity of M pachydermatis isolates obtained from a wide range of hosts was investigated by the partial sequencing of the large subunit (LSU) ribosomal RNA. Among 100 isolates examined, seven types (Ia-Ig) were discriminated on the basis of nucleotide sequence diversity. The seven types differed by one to five mutations, all of them corresponding to transitions. The predominant sequence, type Ia, appeared to be ubiquitous since it was observed in isolates recovered from domestic and wild carnivora, from a monkey and from man. In contrast the sequence types Ic, Id and Ig seemed to be more host-specific; they included isolates recovered exclusively from rhinoceros, dogs and ferrets, respectively. None of the seven sequence types correlated with isolation from healthy skin or a particular lesion (otitis externa or other dermatitis). The study indicated that the skin of an animal may be colonised by more than one type of M pachydermatis.

Epidemiology of nosocomial fungal infections

This paper briefly reviews the current knowledge of the epidemiology and modes of transmission of nosocomial fungal infections and some of the therapeutic options for treating these diseases. In the mid-1980s, many institutions reported that fungi were common pathogens in nosocomial infections. Most, if not all, hospitals care for patients at risk for nosocomial fungal infections. The proportion in all nosocomial infections reportedly caused by Candida spp. increased from 2% in 1980 to 5% in 1986 to 1989. Numerous studies have identified common risk factors for acquiring these infections, most of which are very common among hospitalized patients; some factors act primarily by inducing immunosuppression (e.g., corticosteroids, chemotherapy, malnutrition, malignancy, and neutropenia), while others primarily provide a route of infection (e.g., extensive burns, indwelling catheter), and some act in combination. Non-albicans Candida spp., including fluconazole-resistant C. krusei and Torulopsis (C.) glabrata, have become more common pathogens. Newer molecular typing techniques can assist in the determination of a common source of infection caused by several fungal pathogens. Continued epidemiologic and laboratory research is needed to better characterize these pathogens and allow for improved diagnostic and therapeutic strategies.