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New page: <big><center>'''BACK TO IMMUNOLOGY'''</center></big> <big><center>'''BACK TO HOST INVASION BY MICROORGANISMS'''</...
<big><center>[[Immunology - WikiBlood|'''BACK TO IMMUNOLOGY''']]</center></big>
<big><center>[[Host invasion by microorganisms - WikiBlood|'''BACK TO HOST INVASION BY MICROORGANISMS''']]</center></big>
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=Introduction=
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).
=Major pathogenic fungi=
'''Superficial''': These infections affect only the skin, hair, nails etc.
*Generally not dangerous
*Examples- ''Hortaea werneckii'', causing tinea nigra, and ''Piedraia hortae'', causing black piedra
'''Cutaneous''': Also known as '''dermatophytoses'''
*Only affect superficial keratinized tissue- skin, hair and nails
*Again generally not dangerous
*Examples- ''Candida albicans'', causing candidiasis of the skin and nails, ''Microsporum'' species
'''Subcutaneous''': Usually cause chronic localised infections of the skin and underlying dermis
*Normally reside in soil and vegetation; they enter skin through cuts and grazes
*Can occasionally affect the deep tissues, e.g. bones and muscles
*Examples- ''Sporothrix schenkii'', causing sporotrichosis, ''Madurella mycetomatis'' causing mycetoma
'''Systemic''': Also known as '''deep''', '''endemic''' or '''primary'''
*Usually serious; sometimes fatal
*Examples- ''Histoplasma capsulatum'' causing histoplasmosis, ''Blastomyces dermatitidis'' causing blastomycosis
'''Opportunistic''': Ubiquitous fungi that affect only susceptible hosts; immunocompetent individuals are normally resistant
*Examples- ''Aspergillus fumigatus'', causing aspergilliosis, ''Cryptococcus neoformans'', causing cryptococcosis
=Immunity to fungi=
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.
*T cell immunity- it is thought that helper T cells release cytokines to activate macrophages to fight the infection
*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
<big><center>[[Host invasion by microorganisms - WikiBlood|'''BACK TO HOST INVASION BY MICROORGANISMS''']]</center></big>
----
=Introduction=
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).
=Major pathogenic fungi=
'''Superficial''': These infections affect only the skin, hair, nails etc.
*Generally not dangerous
*Examples- ''Hortaea werneckii'', causing tinea nigra, and ''Piedraia hortae'', causing black piedra
'''Cutaneous''': Also known as '''dermatophytoses'''
*Only affect superficial keratinized tissue- skin, hair and nails
*Again generally not dangerous
*Examples- ''Candida albicans'', causing candidiasis of the skin and nails, ''Microsporum'' species
'''Subcutaneous''': Usually cause chronic localised infections of the skin and underlying dermis
*Normally reside in soil and vegetation; they enter skin through cuts and grazes
*Can occasionally affect the deep tissues, e.g. bones and muscles
*Examples- ''Sporothrix schenkii'', causing sporotrichosis, ''Madurella mycetomatis'' causing mycetoma
'''Systemic''': Also known as '''deep''', '''endemic''' or '''primary'''
*Usually serious; sometimes fatal
*Examples- ''Histoplasma capsulatum'' causing histoplasmosis, ''Blastomyces dermatitidis'' causing blastomycosis
'''Opportunistic''': Ubiquitous fungi that affect only susceptible hosts; immunocompetent individuals are normally resistant
*Examples- ''Aspergillus fumigatus'', causing aspergilliosis, ''Cryptococcus neoformans'', causing cryptococcosis
=Immunity to fungi=
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.
*T cell immunity- it is thought that helper T cells release cytokines to activate macrophages to fight the infection
*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