Fungal infections are caused by microscopic fungus that proliferates due to ideal conditions. Fungal skin infections in humans occur on nails, skin and hair, as it sustains itself on protein keratin which is abundantly found in these areas. Some of the more common fungal infections are: Candida, Aspergillus, Cryptococcus, Histoplasma, Pneumocystis, Stachybotrys
Caused by yeast (type of fungus) infecting the skin or mucous membrane, living in the body in dormant state. It is only when they get optimum conditions, do they multiply and get converted into Candidiasis. It is found as normal flora on the mucous membranes and in the gastrointestinal tract but is usually held in check by: a) normal flora bacteria; and b) normal body defenses. Candida can cause a variety of opportunistic infections in people who are debilitated, immunosuppressed, or have received prolonged antibacterial therapy.
Women who are diabetic, pregnant, taking oral contraceptives or having menopause are also more prone to vaginitis (Novikova et al, 2003). These conditions alter the sugar concentration and pH of the vagina making it more favorable for the growth of Candida. People who are immunosuppressed frequently develop thrush, vaginitis, and sometimes disseminated infections. Any Candida infection is called candidiasis. Candida most commonly causes vaginitis, thrush (an infection of the mouth), balantitis (an infection of the penis), onychomycosis (an infection of the nails), and dermatitis (diaper rash and other infections of moist skin).
Less commonly, Candida can infect the lungs, blood, heart, and meninges, especially in the compromised or immunosuppressed host. Candida now causes about 10% of all cases of septicemia. Candidiasis of the esophagus, trachea, bronchi, or lungs, in conjunction with a positive HIV antibody test, is one of the indicator diseases for AIDS (Kaiser 2012). Candida is said to be dimorphic, that is it has two different growth forms. It can grow as an oval, budding yeast, but under certain culture conditions, the budding yeast may elongate and remain attached producing filament-like structures called pseudohyphae. C. albicans may also produce true hyphae similar to molds. In this case long, branching filaments lacking complete septa form.
The pseudohyphae and hyphae help the yeast to invade deeper tissues after it colonizes the epithelium. Asexual spores called blastoconidia (blastospores) develop in clusters along the hyphae, often at the points of branching.
Under certain growth conditions, thick-walled survival spores called chlamydoconidia (chlamydospores) may also form at the tips or as a part of the hyphae. The most common Candida species causing human infections is C. albicans, causing 50-60% of all Candida infections. Candida glabrata is second, causing 15-20% of Candida infections; Candidaparapsilosis is third, responsible for 10-20%. Symptoms: Includes fungal skin rash, pus filled patches, pimples and aggravated itch on the infected area (Rapini et al, 2007).
2) TineaVersicolor Also known as Pityriasisversicolor, Dermatomycosisfurfuracea and Tineaflava, is more common in adults and adolescents. A rather chronic fungal skin infection causes skin discoloring and occurrence of reddish and brown patches on the epidermis. Symptoms: Non itchy rashes on body with reddish tan colored patches (James et al 2006).
3) Tinea Infections or Ringworm Infection - Misinterpreted for a worm, but is a fungal infection of the skin causing a reddish ring to form. Causes for this fungal skin infection are malnourishment, poor hygiene and warm moist climate, and can be transmitted from an infected person. Symptoms: Itchy ring like scaly patches which later forms pus filled blisters. If it occurs on nail they get crumpled, discolored and thickened. If it is in scalp you can lose scalp hair and get bald patches (James et al 2006).
4) Ringworm - Fungal Skin Infection is further categorized as: * Body ringworm (TineaCorporis) - Can occur anywhere on skin accompanied by ring like formation on affected area. Athlete's foot (TineaPedis or Foot Ringworm) is a fungal skin infection affecting feet. Athlete’s foot causes the skin to get whitened between the toes with itchy rashes. Nail ringworm (TineaUnguium) - Occurs on nails and finger with itchy sensation. Scalp ringworm (TineaCapitis) - A contagious fungal infections of the skin occurring in the hair, scalp and affects children aged between 2 -10. Jock itch (TineaCruris or Groin Ringworm) - Occurs in the groin region followed with intense itch and rash (Rapini 2007).
5) Cryptococcus neoformans
A lesser known but often more serious pathogenic yeast is Cryptococcus neoformans. It has a worldwide distribution, affecting men twice as often as women. The causative agent has been isolated in pigeon excretions. Like many fungi, this yeast can also reproduce sexually and the name given to the sexual form of the yeast is Filobasidiellaneoformans(Kaiser 2012).
It appears as an oval yeast 5-6 µm in diameter, forms buds with a thin neck, and is surrounded by a thick capsule. It does not produce pseudohyphae and chlamydospores. The capsule enables the yeast to resist phagocytic engulfment. The yeast is dimorphic. In its sexual form, as well as in its asexual form under certain conditions, it can produce a hyphal form.
Cryptococcus infections are usually mild or subclinical but, when symptomatic, usually begin in the lungs after inhalation of the yeast in dried bird feces. It is typically associated with pigeon and chicken droppings and soil contaminated with these droppings. Cryptococcus, found in soil, actively grows in the bird feces but does not grow in the bird itself. Usually the infection does not proceed beyond this pulmonary stage. In the immunosuppressed host, however, it may spread through the blood to the meninges and other body areas, often causing cryptococcalmeningoencephalitis (Kaiser 2012).
Although exposure to the organism is probably common, large outbreaks are rare, indicating that an immunosuppressed host is usually required for the development of severe disease. Extrapulmonarycryptococcosis, in conjunction with a positive HIV antibody test, is another indicator disease for AIDS (Cotran et al 2005).
Malasseziaglobosa is a dimorphic yeast that is the most frequent cause of a superficial skin infection called tineaversicolor that commonly appears as a hypopigmentation of the infected skin. M. globosa is also the most common cause of dandruff and seborrheic dermatitis. The yeast is naturally found on the skin (Kaiser 2012).
Sporotrichosis is an infection of farmers, horticulturists, and others who come into contact with plants or mud. The disease affects the skin and lymphatic system and, in rare cases, becomes disseminated (Ryan and Ray 2004).
Blastomycosis is caused by a yeast-like fungus that reproduces by budding. The North American variety, caused by Blastomycosisdermatitidis, occurs more often in men and seems to be limited to the central and E United States and Canada. Wart-like lesions appear most often on the skin, sometimes spreading to the bones and other organs. The South American variety of blastomycosis is caused by B. brasiliensis(James et al 2006).
Among the fungi that infect the deeper tissues is Coccidioidesimmitis, which causes coccidioidomycosis, sometimes called valley fever, a lung infection that is prevalent in the SW United States.
Histoplasmosis, which is caused by spores of the fungal genus Histoplasma is a severe infection that shows varied symptoms. In acute cases ulcers of the pharynx and enlargement of the liver and spleen are present. In other forms tubercular-like lesions of the lung occur.
In its benign form no symptoms may be present. Fungal infections sometimes follow the use of antibiotics, which kill nonpathogenic as well as pathogenic bacteria, thereby providing a free field in the body for fungal invasion. Opportunistic fungal infection occurs when a fungus enters a compromised host, as in the case of such diseases as AIDS (Barron and Madinger, 2008).