Phylogenetic relationship of the genus Malassezia based on mitochondrial cytochrome B gene]

Mitochondrial cytochrome b genes of pathogenic yeasts and fungi were analyzed for identification and phylogenetic relationship. The species of genus Malassezia also were analyzed and each sequence was specific in the same domain of cytochrome b gene. Some species represented intraspecies variation. The structure and function of cytochrome b protein was retained and its substitution rates may be in proportion to the evolutionary period. The deduced amino acid sequence was encoded by each nucleotide sequence of cytochrome b gene, and the phylogenetic tree of eukaryote and basidiomycetous yeast was obtained using this sequence. The species of genus Malassezia formed one cluster in this tree, meaning that the concepts of this genus reflect its evolution. The mitochondrial cytochrome b gene analysis was valuable for the identification and phylogenetic analysis of the genus.     

Update on the genus Malassezia.

Malassezia yeasts are commensals of normal human skin, but also cause pityriasis versicolor, seborrhoeic dermatitis and evidence is accumulating that they play a significant role in atopic eczema/dermatitis syndrome (AEDS; formerly atopic dermatitis). The taxonomy of the genus has changed considerably and is likely to change more in the future. Our understanding of the interaction between Malassezia and the host demonstrates that it has the paradoxical ability to both stimulate and suppress the immune response directed against it and there is a fine balance in its existence at the interface between commensalism and pathogenicity.     

The Malassezia genus in skin and systemic diseases

In the last 15 years, the genus Malassezia has been a topic of intense basic research on taxonomy, physiology, biochemistry, ecology, immunology, and metabolomics. Currently, the genus encompasses 14 species. The 1996 revision of the genus resulted in seven accepted taxa: M. furfur, M. pachydermatis, M. sympodialis, M. globosa, M. obtusa, M. restricta, and M. slooffiae. In the last decade, seven new taxa isolated from healthy and lesional human and animal skin have been accepted: M. dermatis, M. japonica, M. yamatoensis, M. nana, M. caprae, M. equina, and M. cuniculi. However, forthcoming multidisciplinary research is expected to show the etiopathological relationships between these new species and skin diseases. Hitherto, basic and clinical research has established etiological links between Malassezia yeasts, pityriasis versicolor, and sepsis of neonates and immunocompromised individuals. Their role in aggravating seborrheic dermatitis, dandruff, folliculitis, and onychomycosis, though often supported by histopathological evidence and favorable antifungal therapeutic outcomes, remains under investigation. A close association between skin and Malassezia IgE binding allergens in atopic eczema has been shown, while laboratory data support a role in psoriasis exacerbations. Finally, metabolomic research resulted in the proposal of a hypothesis on the contribution of Malassezia-synthesized aryl hydrocarbon receptor (AhR) ligands to basal cell carcinoma through UV radiation-induced carcinogenesis.     

Malassezia and atopic dermatitis]

Although many exacerbating factors for atopic dermatitis (AD) have been discussed, we are focusing on fungus antigen as a pathogenesis for this condition. About half of the patients were sensitized by Candida albicans and/or Malassezia furfur (MF) using IgE. Patients with severe eruption tended to have a higher concentration of specific IgE. IgE to purified antigens such as manganese superoxide dismutase (MnSOD), cyclophilin, and Malf2 from MF was also detected, while the pattern of positive IgE was varied among the patients so that the major allergen could not be determined. Skin testing gave a positive reaction to MF after 24 hours as well as an immediate type reaction; this delayed type reaction was AD specific since a small number of patients with bronchial asthma showed a positive response to MF. Peripheral mononuclear cells co-cultured with crude MF antigen in vitro produced IL-5 in some AD patients. This response was correlated with the severity of facial eruption, indicating that Th2 type response to MF might make these eruptions worse. MF was easily detected from various skin regions,but we were not able to explain why fewer colonies were obtained from a region with dermatitis than from a non-dermatitis region. From these results, we speculate there are patients who have IgE and Th2 cells which respond to MF. The exact mechanism, however, is still obscure as to how normal flora such as MF can react and exacerbate AD. Further investigations should be done to learn more about the relationship between AD and MF.     

Malassezia related diseases]

The genus Malassezia is now divided into eleven species. Different species initiate or aggravate different skin diseases. In seborroheic dermatitis, M. restricta play an important role, while in atopic dermatitis, M. globosa and/or M. restricta are major cutaneous microflora. M. globosa is a causative species of tinea versicolor, and this species is also a causative species of malassezia folliculitis. We should therefore obtain better knowledge of the ecological and pathogenic roles of malassezia.     

Pityriasis versicolor and Malassezia folliculitis]

Pityriasis versicolor and malassezia folliculitis were studied clinically and mycologically. The main results were as follows: 1) The average age of pityriasis versicolor patients has gradually become higher. 2) Negative rates of Malassezia furfur after treatment were very high by direct examination but relatively low by culture. 3) Patients who were negative by culture on completion of treatment seldom recurred within 2 months. 4) We can evaluate the effectiveness of antifungal application by using Malassezia furfur as normal skin flora on the volunteer's back. 5) Malassezia furfur (orbiculare or ovale type) is detected in follicular contents of steroid acne and acne vulgaris, which makes it necessary to establish criteria for diagnosis of malassezia folliculitis.     

TB vaccines: progress and problems

Tuberculosis (TB) is the biggest killer worldwide of any infectious disease, a situation worsened by the advent of the HIV epidemic and the emergence of multi-drug resistant strains of Mycobacterium tuberculosis. The existing vaccine, Mycobacterium bovis bacille Calmette-Guérin (BCG), has proven inefficient in several recent field trials. There is currently intense research using cutting-edge vaccine technology to combat this ancient disease. However, it is necessary to understand why BCG has failed before we can rationally develop the next generation of vaccines. Several hypotheses that might explain the failure of BCG and the strategies designed to address these shortcomings are discussed.     

Taxonomy, epidemiology, and clinical relevance of the genus Arcobacter

The genus Arcobacter, defined almost 20 years ago from members of the genus Campylobacter, has become increasingly important because its members are being considered emergent enteropathogens and/or potential zoonotic agents. Over recent years information that is relevant for microbiologists, especially those working in the medical and veterinary fields and in the food safety sector, has accumulated. Recently, the genus has been enlarged with several new species. The complete genomes of Arcobacter butzleri and Arcobacter nitrofigilis are available, with the former revealing diverse pathways characteristic of free-living microbes and virulence genes homologous to those of Campylobacter. The first multilocus sequence typing analysis showed a great diversity of sequence types, with no association with specific hosts or geographical regions. Advances in detection and identification techniques, mostly based on molecular methods, have been made. These microbes have been associated with water outbreaks and with indicators of fecal pollution, with food products and water as the suspected routes of transmission. This review updates this knowledge and provides the most recent data on the taxonomy, species diversity, methods of detection, and identification of these microbes as well as on their virulence potential and implication in human and animal diseases.     

Cutaneous immune and inflammatory reactions to Malassezia furfur]

Initiation and aggravation of several inflammatory skin diseases are associated with Malassezia furfur. These are divided into at least two groups. In one group including tinea versicolor and Malassezia folliculitis, the growth of Malassezia furfur directly triggers the development of the cutaneous lesions. In another group including atopic dermatitis, seborrheic dermatitis, and psoriasis, cutaneous lesions already developed by other mechanisms are aggravated by the growth of Malassezia furfur. Recent progress of molecular biology techniques revealed that Malassezia furfur is divided into at least seven species. Since their clinical and histological findings are quite diverse, their differences cannot be explained solely by the difference in antigenicity of each Malassezia. Instead, the cutaneous defense mechanisms against Malassezia furfur must be considered. In this article, we reviewed the mechanisms at three levels: 1) barrier functions of the uppermost layer of the skin, the stratum corneum, 2) cytokine production by epidermal keratinocytes, and 3) immune and inflammatory responses by infiltrating neutrophils and T cells.     

Relationship between Malassezia Yeast and Infantile Seborrhoeic Dermatitis]

We examined 52 patients with infantile seborrhoeic dermatitis (ISD) and 47 healthy 1-month-old infants. Yeast cells on the right side of the face were counted by direct microscopic examination, and isolates from the left side of the face were identified by Tween test. Yeast cells were more numerous patients with ISD than in the healthy infants. M. furfur and M. globosa were isolated from ISD patients at significantly higher rates than from healthy infants.     

Familial Alzheimer's disease: progress and problems

This paper reexamines recent epidemiologic and molecular genetic studies on the genetic basis of Alzheimer's Disease (AD). Careful analysis of the available epidemiologic data strongly suggests that at least a proportion of AD results from the inheritance of an autosomal dominant gene defect. However, studies of isolated families, of concordance rates in twins, and of risk for AD in relatives of AD probands yield conflicting data. While it is likely that much of the conflict can be ascribed to methodologic differences, it remains premature to conclude that all AD is transmitted as an autosomal dominant trait. Molecular genetic techniques hold the promise of isolation and characterization of the genetic defect(s) in familial AD (FAD). Recently, chromosome 21 has been implicated as the potential site of an autosomal dominant defect in some but not necessarily all FAD pedigrees. However, the results of recent genetic epidemiologic studies suggest that progress in the molecular genetic approach to AD will be difficult.     

Mucosal viral vaccines: progress and problems

Data obtained in the recent years on developing the viral inactivated mucosal vaccines by applying the mucosal-adhesive adjuvants are presented in the survey. Progress achieved in designing the mucosal influenza vaccines and mucosal vaccines against a variety of other viral infections is pointed out. Cross-protection against variations of a virus within its subtype limits as well as overcoming of a negative influence of parent antibodies produced on the immunogenicity of live-vaccines', which were used at young age, were observed in the intranasal administration of viral mucosal vaccines. A number of shortcomings of bacterial toxins used as mucosal-adhesive adjuvants as well as problems, which may arise when the viral mucosal vaccines are used on a large-scale basis due to a need in their two- and-threefold intranasal administration, are in the focus of attention.     

Hepatitis C: progress and problems.

The hepatitis C virus (HCV), a single-stranded RNA virus, is the major cause of posttransfusion hepatitis. HCV isolates differ in nucleotide and amino acid sequences. Nucleotide changes are concentrated in hypervariable regions and may be related to immune selection. In most immunocompetent persons, HCV infection is diagnosed serologically, using antigens from conserved regions. Amplification of RNA may be necessary to detect infection in immunosuppressed patients. Transmission by known parenteral routes is frequent; other means of spread are less common and may represent inapparent, percutaneous dissemination. Infection can lead to classical acute hepatitis, but most infected persons have no history of acute disease. Once infected, most individuals apparently remain carriers of the virus, with varying degrees of hepatocyte damage and fibrosis ensuing. Chronic hepatitis may lead to cirrhosis and hepatocellular carcinoma. However, disease progression varies widely, from less than 2 years to cirrhosis in some patients to more than 30 years with only chronic hepatitis in others. Determinants important in deciding outcome are unknown. Alpha interferon, which results in sustained remission in selected patients, is the only available therapy. Long-term benefits from such therapy have not been demonstrated. Prevention of HCV infection by vaccination is likely to be challenging if ongoing viral mutation results in escape from neutralization and clearance.     

The genus Campylobacter: a decade of progress.

In 1977, microbiologists and clinicians were awakened to the importance of the genus Campylobacter when it was learned that one species, Campylobacter jejuni, was a major cause of human enteritis. In the following decade substantial advances were made in diagnosis, isolation technology, identification, classification, serotyping, and epidemiology. The genus has undergone rapid expansion as advantage was taken of the deoxyribonucleic acid-deoxyribonucleic acid hybridization technique in defining new species. The 14 species now included in the genus, however, constitute a widely diverse group, and one species, C. pylori, which is associated with human gastroduodenitis, is under consideration for reassignment to another genus. The nomenclature of the subspecies of C. fetus has been resolved and the role of C. fetus subsp. fetus as an agent of human infections has been more clearly defined. The thermophilic campylobacteria that are etiological agents of human enteritis now include three species, C. jejuni, C. coli, and C. laridis. Recently defined species that have also been implicated as enteritis-causing agents include C. hyointestinalis, "C. upsaliensis," "C. cinaedi," and "C. fennelliae." The aerotolerant campylobacteria are now included in the species C. cryaerophila, and the campylobacteria isolated from salt marshes are included in C. nitrofigilis. The taxonomy and nomenclature of C. sputorum have been revised. C. sputorum now consists of three biovars (biotypes). Two of these, biovar sputorum and biovar bubulus, were previously considered to be separate subspecies and the third, biovar fecalis, was previously regarded as a separate species and known as "C. fecalis." The former subspecies C. sputorum subsp. mucosalis has been elevated to the rank of species. C. mucosalis is metabolically closely related to C. consisus. Human pathogens have not been identified among C. sputorum, C. mucosalis, or C. concisus. The goal of this article is to review developments during the last 10 years with emphasis on changes in taxonomy that are important from the perspective of the clinical microbiologist.     

Atopic dermatitis and Malassezia species: a study of antigenic components of Malassezia species for immunoglobulin E of patients with atopic dermatitis]

Antigenic components extracted by treatment with beta-mercaptoethanol from M. furfur, M. globosa, M. restricta, M. slooffiae, and M. sympodialis were studied for immunoglobulin E antibodies in sera of patients with atopic dermatitis. CBB staining and lectin blots of the extracts showed that each Malassezia species contained species-dependent components at the protein level. In a Western blot with the 2-ME extracts,IgE antibodies against the Malassezia species were found in sera of 83% (for M. globosa), 74% (for M. sympodialis), 65% (for M. furfur), 56% (for M. restricta) and 50% (for M. slooffiae) of the AD patients. In the Western blot inhibition test, the 2-ME extract of M. globosa partially inhibited the reaction of the antigenic components of other Malassezia species with the patients IgE antibodies. These results indicated that Malassezia species contained both species-specific and common antigenic components at the IgE antibody level. A major component of M. globosa was isolated from the 2-ME extract of this fungus by ion-exchange column chromatography and was referred to as Malg46b. Dot blot with the Malg46b containing fraction immunologically reacted with 69% of the sera of the patients, and with 83% of the sera of those who were positive for IgE antibodies to the 2-ME extract of M. globosa in Western blot. The intensities generated for each dot correlated well with the total intensities generated for the 2-ME extract of M. globosa in Western blot (r=0.763) The polyclonal antibody to Malg46b reacted strongly only with the 2-ME extract of M. globosa and reacted slightly with M. restricta. These results indicate that a glycoprotein, Malg46b of M. globosa, is dominantly expressed in this fungus and is a possible major antigen for IgE antibodies in patients with AD.