fungal infection

fungal infection

fungal infection, infection caused by a fungus (see Fungi), some affecting animals, others plants.

Fungal Infections of Human and Animals

Many fungal infections, or mycoses, of humans and animals affect only the outer layers of skin, and although they are sometimes difficult to cure, they are not considered dangerous. Athlete's foot and ringworm are among the common superficial fungal infections. Fungal infections of the mucous membranes are caused primarily by Candida albicans (see candidiasis). It usually affects the mouth (see thrush) and the vaginal and anal regions.

The fungi that affect the deeper layers of skin and internal organs are capable of causing serious, often fatal illness. 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. Blastomycosis is caused by a yeastlike fungus that reproduces by budding. The North American variety, caused by Blastomycosis dermatitidis, occurs more often in men and seems to be limited to the central and E United States and Canada. Wartlike 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. Chytridiomycosis, caused by Batrachochytrium dendrobatidis, is a deadly fungal skin infection in amphibians, which it kills by damaging to the animals' normally permeable skin, thus disrupting the transport of air and moisture.

Among the fungi that infect the deeper tissues is Coccidioides immitis, which causes coccidioidomycosis, sometimes called valley fever, a lung infection that is prevalent in the SW United States. Cryptococcosis is another fungus disease that may be localized in the lung or disseminated, especially to the central nervous system. It has a worldwide distribution, affecting men twice as often as women. The causative agent (Cryptococcus neoformans) has been isolated in pigeon excretions. 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 tubercularlike 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. Treatment for fungal infections includes systemic antifungal agents, such as amphotericin B, fluconazole, and itraconazole, and agents usually used topically, such as clotrimazole (Lotrimin) and miconazole (Monistat).

Fungal Infections of Plants

Serious damage is done to crops each year by fungal infections of plants such as smuts, rusts, ergots, and mildews. Dutch elm disease, a disease that has seriously depleted the number of elm trees in the United States, is caused by the fungus Ceratostomella ulmi. Such diseases are usually fought with fungicides or by developing resistant plants. See also diseases of plants.

A fungal keratitis is an 'inflammation of the eye's cornea' (called keratitis) that results from infection by a fungal organism. Keratomycosis is the Latin terminology equivalent of fungal keratitis - it is the fungal infection of the cornea, the anterior part of the eye which covers the pupil. Those experiencing these symptoms are typically advised to immediately visit the appropriate eyecare professional.

Classification

Infectious keratitis can be bacterial, fungal or viral. Remarkable differences in presentation of the patient allows presumptive diagnosis by the eye care professional, helping in institution of appropriate anti-infective therapy.

Signs and symptoms

The symptoms of fungal keratitis are blurred vision, a red and painful eye that does not improve when contact lenses are removed, increased sensitivity to light, and excessive tearing or discharge. The slit lamp examination shows a corneal ulcer with satellite lesions in the surrounding cornea. There can be associated hypopyon and may even extend to the posterior segment to cause endophthalmitis in later stages, leading to the destruction of the eye.

Causes

Filamentous fungi

Yeasts

Pathophysiology

The precipitating event for fungal keratitis is trauma with a vegetable / organic matter. A thorn injury, or in agriculture workers, trauma with a wheat plant while cutting the harvest is typical. This implants the fungus directly in the cornea. The fungus grows slowly in the cornea and proliferates to involve the anterior and posterior stromal layers. The fungus can break through the descemet's membrane and pass into the anterior chamber. The patient presents a few days or weeks later with fungal keratitis.

Diagnosis

The diagnosis is made by an ophthalmologist correlating typical history, symptoms and signs. A definitive diagnosis is established only after a positive culture report, typically taking a week, from the corneal scraping. Recent advances have been made in PCR / immunologic tests which can give a much quicker result.

Treatment and management

A presumptive diagnosis of fungal keratitis requires immediate empirical therapy. Natamycin ophthalmic suspension is the drug of choice for filamentous fungal infection. Fluconazole ophthalmic solution is recommended for Candida infection of the cornea. Amphotericin B eye drops may be required for non-responding cases, but can be quite toxic and requires expert pharmacist for preparation. Other medications have also been tried with moderate success. consult your eye care professional in any case as they will have the best treatment.

Prognosis

The infection typically takes a long time to heal, since the fungus itself is slow growing. Corneal perforation can occur in patients with untreated or partially treated infectious keratitis and requires surgical intervention in the form of corneal transplantation.

Prevention/Screening

Prevention of trauma with vegetable / organic matter, particularly in agricultural workers while harvesting can reduce the incidence of fungal keratitis. Wearing of broad protective glasses with side shields is recommended for people at risk for such injuries.

Epidemiology

This disease is quite common in the tropics and with large agrarian population. India has a high number of cases with fungal keratitis, but poor reporting system prevents accurate data collection. Florida in US regularly reports cases of fungal keratitis, with Aspergillus and Fusarium spp. as the most common causes.

Social impact

The loss of vision with fungal keratitis can be quite disabling in terms of economic impact and social consequences. Many people come with fungal keratitis in the only eye and thus become blind due to the disease. The lack of education and proper eye protection in such cases is evidently responsible for their plight.

Notable cases

Recently, one particular product, ReNu with MoistureLoc brand of soft contact lens solutions made headlines regarding a report from the United States Centers for Disease Control and Prevention suggesting an increased incidence of a specific type of fungal keratitis (Fusarium keratitis) in people using Bausch & Lomb products. Bausch & Lomb subsequently suspended, then recalled, shipments of one particular product, ReNu with MoistureLoc.

References

See also

External links

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