Monograph on Dimorphic Fungi A guide for classification, isolation and identification of dimorphic fungi, diseases caused by them, diagnosis and treatment By Mohamed Refai and Heidy Abo El-Yazid Department of Microbiology, Faculty of Veterinary Medicine, Cairo University 2014 1 Preface When I see the analytics made by academia.edu for the visitors to my publication has reached 244 in 46 countries in one month only, this encouraged me to continue writing documents for the benefit of scientists and students in the 5 continents. In the last year I uploaded 3 monographs, namely 1. Monograph on yeasts, Refai, M, Abou-Elyazeed, H. and El-Hariri, M. 2. Monograph on dermatophytes, Refai, M, Abou-Elyazeed, H. and El-Hariri, M. 3. Monograph on mycotoxigenic fungi and mycotoxins, Refai, M. and Hassan, A. Today I am uploading the the 4th documents in the series of monographs Monograph on dimorphic fungi, Refai, M. and Abou-Elyazeed, H. Prof. Dr. Mohamed Refai, 2.3.2014 Country 30 day views Egypt 51 2 Country 30 day views Ethiopia 22 the United States 21 Saudi Arabia 19 Iraq 19 Sudan 14 Uganda 12 India 11 Nigeria 9 Kuwait 8 the Islamic Republic of Iran 7 Brazil 7 Germany 6 Uruguay 4 the United Republic of Tanzania 4 ? 4 Libya 4 Jordan 4 Pakistan 3 the United Kingdom 3 Algeria 3 the United Arab Emirates 3 South Africa 2 Turkey 2 3 Country 30 day views the Philippines 2 the Netherlands 2 Sri Lanka 2 Lebanon 2 Trinidad and Tobago 1 Thailand 1 Sweden 1 Poland 1 Peru 1 Malaysia 1 Myanmar 1 Morocco 1 Lithuania 1 Jamaica 1 Italy 1 Hong Kong 1 Finland 1 China 1 Canada 1 Botswana 1 Belgium 1 Australia 1 Argentina 4 1. Introduction 1.1. Definition of dimorphic fungi Dimorphic fungi are those fungi that exist either in yeast form or as mould (mycelial form) depending on environmental conditions, physiological conditions of the fungus or the genetic characteristics. As yeasts. dimorphic fungi exist as single cells and multiply by old cells producing daughter cells. As moulds, dimorphic fungi consist of highly polarized fibrillar cells, which elongate by apical growth, placing cross walls called septa at regular intervals, or remain non-septated, exhibit incomplete cell separation, have the capacity to generate new foci by branching and are generally multinucleate. The ability to alternate between the yeast and filamentous growth forms is a tightly regulated process known as dimorphic switching. Interestingly, for most pathogenic dimorphic fungi only one growth form predominates during infection. Penicillium marnefei Blastomyces dermatitidis 5 1. 2. Classification of dimorphic fungi 1. 2.1. Scientific classification of dimorphic fungi: Dimorphism is common with some members of the major divisions of the fungal kingdom, i.e., Zygomycota, Ascomycota, Basidiomycota, and mitosporic fungi. The following are the known dimorphic fungi: i. Ascomycetes 1. Blastomyces dermatitidis 2. Coccidioides immitis 3. Coccidioides posadasii 4. Histoplasma capsulatum 5. Histoplasma capsulatum var.duboisii 6. Histoplasma capsulatum var.farcimonsum 7. Paracoccidioides brasiliensis 8. Lacazia loboi 9. Penicillium marneffei 10. Sporothrix schenckii 11. Candida albicans 12. Yarrowia lipolytica 13. Aureobasidium pullulans 14. Hortaea werneckii 15. Wangiella dermatitidis 16. Emmonsia parva 17. Emmonsia crescens 18. Beauvera bassiena 19. Metarhizium species ii. Zygomycetes 20. Mucor bacilliformis 21. Mucor circinelloides 22. Mucor genevensis 23. Mucor racemosus 24. Mucor rouxii iii. Basidiomycetes 25. Malassezia furfur 26. Ustilago mayadis 6 1. 2. 2. Classification of dimorphic fungi according to the saprophytic phase morphology i. Dimorphic moulds 1. Blastomyces dermatitidis 2. Coccidioides immitis 3. Coccidioides posadasii 4. Histoplasma capsulatum 5. Histoplasma capsulatum var.duboisii 6. Histoplasma capsulatum var.farcimonsum 7. Paracoccidioides brasiliensis 8. Lacazia loboi 9. Penicillium marneffei 10. Sporothrix schenckii 11. Emmonsia parva 12. Emmonsia crescens 13. Beauvera bassiena 14. Metarhizium species 15. Mucor bacilliformis 16. Mucor circinelloides 17. Mucor genevensis 18. Mucor racemosus 19. Mucor rouxii ii. Dimorphic yeasts 1. Candida albicans 2. Yarrowia lipolytica 3. Malassezia furfur 4. Aureobasidium pullulans 5. Hortaea werneckii 6. Wangiella dermatitidis 1. 2. 3. Classification of dimorphic fungi according to the route of infection 1. 2. 3. 1. Pulmonary infection 1. Blastomyces dermatitidis 2. Coccidioides immitis 3. Coccidioides posadasii 7 4. Histoplasma capsulatum 5. Histoplasma capsulatum var.duboisii 6. Histoplasma capsulatum var.farcimonsum 7. Paracoccidioides brasiliensis 8. Penicillium marneffei 9. Emmonsia parva 10. Emmonsia crescens 11. Lacazia loboi 12. Mucor bacilliformis 13. Mucor circinelloides 14. Mucor genevensis 15. Mucor racemosus 16. Mucor rouxii 1. 2. 3. 2. Skin infection 1. Sporothrix schenckii 2. Lacazia loboi 3. Aureobasidium pullulans 4. Hortaea werneckii 5. Wangiella dermatitidis 6. Malassezia furfur 1.2.3.3. Multiple routes of infection 1. Candida albicans 1. 2. 4. Classificaation of dimorphic fungi according to pathogenicity 1. 2. 4. 1. Pathogenic dimorphic fungi 1. Blastomyces dermatitidis 2. Coccidioides immitis 3. Coccidioides posadasii 4. Histoplasma capsulatum 5. Histoplasma capsulatum var.duboisii 6. Histoplasma capsulatum var.farcimonsum 7. Paracoccidioides brasiliensis 8. Penicillium marneffei 1. 2. 4. 2. Opportunistic pathogenic dimorphic fungi 1. Sporothrix schenckii 2. Candida albicans 8 3. Malassezia furfur 4. Aureobasidium pullulans 5. Hortaea werneckii 6. Wangiella dermatitidis 7. Lacazia loboi 8. Emmonsia parva 9. Emmonsia crescens 1. 2. 4. 3. Insect pathogenic dimorphic fungi 1. Beauvera bassiena 2. Metarhizium 1. 2. 4. 4. Plant pathogenic dimorphic fungi 1. Ustilago mayadis 1. 2. 4. 5. Non-pathogenic dimorphic fungi 1. Yarrowia lipolytica 1. 3. Factors inducing dimorphism 1. 3. 1. Thermally dimorphic fungi: Some dimorphic fungi switch to yeast or mould form depending on the prevailing temperature. These are: 3. Blastomyces dermatitidis 4. Coccidioides immitis 5. Coccidioides posadasii 6. Histoplasma capsulatum 7. Histoplasma capsulatum var.duboisii 8. Histoplasma capsulatum var.farcimonsum 9. Paracoccidioides brasiliensis 10. Penicillium marneffei 11. Sporothrix schenckii 12. Emmonsia parva 13. Emmonsia crescens 9 The physiological changes that occur during the mycelial- to yeast-phase transitions induced by a temperature shift from 25 to 37°C can be divided into three stages: I. The triggering event is a heat-related insult induced by the temperature shift which results in partial uncoupling of oxidative phosphorylation and declines in cellular ATP levels, respiration rates, a. and concentrations of electron transport components. II. The cells then enter a stage in which spontaneous respiration ceases. Cysteine is required for the operation of shunt pathways which permit electron transport to bypass blocked portions of the cytochrome system. III. Finally, there is a shift into a recovery phase during Which transformation to yeast morphology occurs. 1.3.2. Common critical factors that induce yeast growth of Mucor species include: Oxygen concentration (anaerobic conditions), CO2 concentration (high CO2 environments) Carbon source Inhibition of mitochondrial function by potassium cyanide and antimycin A Inhibition of the synthesis of cytochrome b by chloramphenicol Inhibition of lipid metabolism by cerulenin Adding cyclic AMP (cAMP) to the culture medium induces yeast growth of Mucor spp. The following are the dimorphic Mucor species: 1. Mucor bacilliformis 2. Mucor circinelloides 3. Mucor genevensis 4. Mucor racemosus 5. Mucor rouxii 1. 3. 3. Dimorphism and virulence In some pathogenic fungi, dimorphism has been correlated with virulence because along the infection process, dimorphic transitions are often 11 required. Two well-known organisms for which dimorphism have been studied are the pathogenic fungi 1. Candida albicans and 2. Ustilago maydis C. albicans is able to grow in two different ways; reproduction by budding, forming an ellipsoid bud, and in hyphal form, which can periodically fragment and give rise to new mycelia, or yeast-like forms. Transitions between the two phenotypes can be induced in vitro in response to several environmental cues such as pH or temperature, or different compounds such as Nacetylglucosamine or proline. However, perhaps the most critical criterion for pathogenicity is the induction of the mycelial form by serum or macrophages. In addition to the intrinsic biological interest of this dimorphism, its ability to switch between the yeast and the hyphal mode of growth has been implicated in its pathogenicity In Ustilago maydis, the causal agent of corn smut, the morphological transition from yeast to filamentous growth is inextricably linked to pathogenicity; budding haploid cells are saprobic and, upon mating of compatible strains, the fungus converts to dikaryotic filamentous growth and obligate parasitism. The filamentous dikaryon proliferates in the host plant, inducing tumor formation and undergoing additional morphological changes that eventually result in the production of melanized diploid teliospores. 1.3.4. Dimorphism in Lacazia loboi Although the invasive cells of L. loboi in the tissues of infected humans and other animals are abundant and readily detectable histologically, they have been intractable to isolation and culture. The phylogenetic analysis of the 18S DNA the close relation to P. brasiliensis and also close to the other systemic dimorphic fungal pathogens