Microbiology Lecture 5

Introduction to Fungi

Importance of fungi

• Production of antibiotics (e.g. penicillins), cyclosporins (immunosuppressants in transplant surgery), modification of steroids (for contraceptives)
• ‘Cellular factories’ for producing heterologous (foreign) gene products e.g. yeast production of hepatitis B vaccine
• Decomposition of complex plant and animal remains in natural environments such as soil
• Rotting of food, textiles etc. etc. including timber

Fungal pathogens of plants

Fungi are the most important causes of crop diseases, responsible for billions of pounds worth of damage each year and for periodic devastating disease epidemics.

Fungal pathogens of humans

In contrast to the many fungal parasites of plants, there are only about 200 fungi that infect humans.

Humans have a high degree of innate immunity to fungi, with the exception of the dermatophytic fungi, which commonly cause infections of the skin, nails and hair.

With the advance of AIDS and the increasing role of transplant surgery, however, fungi are becoming one of the most significant causes of death of immuno-compromised and immunosuppressed patients.

There are relatively few antifungal drugs available to treat the major fungal infections of man. 

Fungal diseases

Fungal infections (mycoses) of humans fall into three categories.

Superficial mycoses- These infections are confined to the outer layers of epithelia i.e. skin, hair or nails. 

Subcutaneous mycoses- These involve deeper layers of the skin and a different group of organisms. 

Systemic mycoses- Are the most serious category of fungal infections. The infecting fungi in this category penetrate the epithelia into the bloodstream and spread throughout the body. 

Candidiasis

The Candida species…