Fungi can be broadly classified into two groups;  yeasts and molds. Yeasts are single celled  organisms that reproduce by budding but molds grow as filaments like structure. Many medically important fungi shows unique behaviour based on temperature of growth and habitat, which is known as dimorphism (di: both, morphism: morphological form). These dimorphic fungi exists as molds in the environment at ambient temperature (25°C– 30°C ) and as yeasts (or other structure e.g., spherules in case of Coccidioides immitis) in human tissues at body temperature (35°C -37°C).
Dimorphic fungi and their properties 
Most of the dimorphic fungi causes systemic mycoses and Sporothrix (one of the dimorphic fungus) causes subcutaneous mycoses.
Dimorphic fungi causing systemic mycoses
Inhalation of spores of these dimorphic fungi causes systemic mycoses.
  1. Histoplasma capsulatum: H. capsulatum is a dimorphic fungus that exists as a mold in soil and as a yeast in tissue. It causes histoplasmosis. (Note: It does not possess capsule)
  2. Blastomyces dermatitidis: B. dermatitidis is a dimorphic fungus that exists as a mold in a soil and spherule in tissue. The yeast has a characteristic double refractive wall and a single broad based bud.
  3. Paracoccidioides brasiliensis: P. brasiliensis is a dimorphic fungus that exists as a mold in soil and yeasts in tissue. The yeast is thick walled and have multiple buds. It causes South American Blastomycosis.
  4. Coccidioides immitis: It is a dimorphic fungus that exists as a mold in soil and as a yeast in a tissue. It causes coccidioidomycosis.
    coccidioides
    Coccidioides immitis – arthroconidia Dr Arthur DiSalvo
Among the subcutaneous mycoses causing fungi, Sporothrix schenckii is a notable dimorphic fungus. It causes sporotrichosis.
Penicillium marneffei is a mould fungus with a yeast form in tissues. It is a opportunistic pathogen causing systemic penicilliosis in AIDS patients in Thailand, China, Hongkong, Vietnam and other parts of Southeast Asia.
Mneomonics to remember Dimorphic Fungi: 
  1. Mold in the Cold, Yeast in the Heat (Beast)
  2. Body Heat  Probably Changes ShaPe of the dimorphic fungi
    • Blastomyces
    • Histoplasma
    • Paracoccidioides  immitis
    • Coccidioides
    • Sporothrix
    • Penicillium marneffei
 Bacteriology Notes Are here

Related Posts:

  • Catalase Test Catalase is an enzyme, which is produced by microorganisms that live in oxygenated environments to neutralize toxic forms of oxygen metabolites; H2O2.  The catalase enzyme neutralizes the bactericidal effects of hydr… Read More
  • Gram Negative Cocci Neisseria species : The genus Neisseria contains 12 species, two of which, N.meningitidis and N. gonorrhoeae, are commonly pathogenic in humans. Both may cause infections in the CNS, … Read More
  • Gram Negative Coccobacilli A coccobacillus is a type of bacterium with a shape intermediate between cocci and bacilli i.e., they are very short rods which may be mistaken for cocci. These small, pleomorphic gram-negative bacteria range in shape … Read More
  • Löwenstein–Jensen (LJ) Medium Preparation of Media Ingredients A.  Mineral salt solution Potassium dihydrogen phosphate anhydrous (KH2PO4): 2.4 g Magnesium sulphate anhydrous: (MgSo4.7H20): 0.24 g Magnesium citrate: 0.6 g Asparagine: 3.6 g Gly… Read More
  • Nutrient agar short note Nutrient agar is used as a general purpose medium for the growth of a wide variety of non-fastidious microorganisms. It consists of peptone, beef extract and agar. This relatively simple formulation provides … Read More

0 Comments:

Powered by Blogger.

Visitors

199174
Print Friendly Version of this pagePrint Get a PDF version of this webpagePDF


 download University Notes apps for android

Popular Posts

Flag Counter