Difference between revisions of "Fungi"

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{{toplink
 
|backcolour = FFE4E1
 
|linkpage =Immunology - WikiBlood
 
|linktext =IMMUNOLOGY
 
|sublink1 =Host invasion by microorganisms - WikiBlood
 
|subtext1 =HOST INVASION BY MICROORGANISMS
 
|sublink2 =Fungi
 
|subtext2 =INFECTIOUS AGENTS AND PARASITES
 
|pagetype =Blood
 
}}
 
=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).
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#REDIRECT[[:Category:Fungi]]
 
 
=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
 

Latest revision as of 12:45, 28 May 2010

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