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| − | <big><center>[[Immunology - WikiBlood|'''BACK TO IMMUNOLOGY''']]</center></big>
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| − | <big><center>[[Host invasion by microorganisms - WikiBlood|'''BACK TO HOST INVASION BY MICROORGANISMS''']]</center></big>
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| − | ----
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| − | =Introduction=
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| − | Although there are over 50,000 identified species of fungi, only a few hundred are known to be pathogenic, causing infections known as mycoses (mycology being the study of fungi). Fungi are nonphotosynthetic organisms with a eukaryotic cell structure and are able to grow as branching or filamentous forms (mycelia) or as single cells (yeasts).
| + | #REDIRECT[[:Category:Fungi]] |
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| − | =Major pathogenic fungi=
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| − | '''Superficial''': These infections affect only the skin, hair, nails etc.
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| − | *Generally not dangerous
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| − | *Examples- ''Hortaea werneckii'', causing tinea nigra, and ''Piedraia hortae'', causing black piedra
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| − | '''Cutaneous''': Also known as '''dermatophytoses'''
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| − | *Only affect superficial keratinized tissue- skin, hair and nails
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| − | *Again generally not dangerous
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| − | *Examples- ''Candida albicans'', causing candidiasis of the skin and nails, ''Microsporum'' species
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| − | '''Subcutaneous''': Usually cause chronic localised infections of the skin and underlying dermis
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| − | *Normally reside in soil and vegetation; they enter skin through cuts and grazes
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| − | *Can occasionally affect the deep tissues, e.g. bones and muscles
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| − | *Examples- ''Sporothrix schenkii'', causing sporotrichosis, ''Madurella mycetomatis'' causing mycetoma
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| − | '''Systemic''': Also known as '''deep''', '''endemic''' or '''primary'''
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| − | *Usually serious; sometimes fatal
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| − | *Examples- ''Histoplasma capsulatum'' causing histoplasmosis, ''Blastomyces dermatitidis'' causing blastomycosis
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| − | '''Opportunistic''': Ubiquitous fungi that affect only susceptible hosts; immunocompetent individuals are normally resistant
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| − | *Examples- ''Aspergillus fumigatus'', causing aspergilliosis, ''Cryptococcus neoformans'', causing cryptococcosis
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| − | =Immunity to fungi=
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| − | Cutaneous and superficial fungal infections are normally self-limiting, with recovery associated with a resistance to re-infection. As hosts often develop delayed-type hypersensitivity, this resistance appears to be cell-mediated.
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| − | *T cell immunity- it is thought that helper T cells release cytokines to activate macrophages to fight the infection
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| − | *Neutrophils- there is now growing evidence for the role of neutrophils in some infections of the respiratory system, with defensin and the nitric oxide pathways implicated
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