Microbial agents of disease : Fungi & Protozoa

FUNGAL DISEASE

Fungal diseases are called mycoses and those affecting humans can be divided into four groups based on the level of penetration into the body tissues:

Superficial mycoses are caused by fungi that grow only on the surface of the skin or hair.
Cutaneous mycoses or dermatomycoses include such infections as athlete's foot and ringworm, in which growth occurs only in the superficial layers of skin, nails, or hair.
Subcutaneous mycoses penetrate below the skin to involve the subcutaneous, connective, and bone tissue.
Systemic or deep mycoses are able to infect internal organs and become widely disseminated throughout the body. This type is often fatal.
The most common type of subcutaneous mycosis seen worldwide is sporotrichosis, which occurs most often in gardeners and farmers who come in direct contact with soil. This is a chronic infection caused by the fungus Sporothrix schenckii, occurring in three forms. The 'cutaneous lymphatic form' is characterized by a single pustule or nodule that forms at the site of invasion. This is followed by lymphatic spread and the development of numerous subcutaneous lesions. This 'disseminated form' is marked by multiple, painless cutaneous or subcutaneous nodules, which can form into ulcers or abscesses involving the muscles, joints, bones, eyes, gastrointestinal system, mucous membranes, and nervous system. The 'pulmonary form' results from the inhalation of spores, but produces much the same forms of the disease.

Other forms of subcutaneous mycoses occur mostly in the tropics and subtropics and are caused by several fungal species. These conditions are called chromomycosis (producing wartlike nodules that can ulcerate) and maduromycosis (or mycetoma -- a chronic slowly progressive destructive infection involving several layers of skin, producing abscessing granulomas). Treatment is difficult and often requires surgical removal of the offending tissues.