Fungal infections


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Fungal infections

Several thousand species of fungi have been described, but fewer than 100 are routinely associated with invasive diseases of humans. In general, healthy humans have a very high level of natural immunity to fungi, and most fungal infections are mild and self-limiting. Intact skin and mucosal surfaces and a functional immune system serve as the primary barriers to colonization by these ubiquitous organisms, but these barriers are sometimes breached.

Unlike viruses, protozoan parasites, and some bacterial species, fungi do not require human or animal tissues to perpetuate or preserve the species. Virtually all fungi that have been implicated in human disease are free-living in nature. However, there are exceptions, including various Candida spp., which are frequently found on mucosal surfaces of the body such as the mouth and vagina, and Malassezia furfur, which is usually found on skin surfaces that are rich in sebaceous glands. These organisms are often cultured from healthy tissues, but under certain conditions they cause disease. Only a handful of fungi cause significant disease in healthy individuals. Once established, these diseases can be classified according to the tissues that are initially colonized.

Superficial mycoses

Four infections are classified in the superficial mycoses. Black piedra, caused by Piedraia hortai, and white piedra, caused by Trichosporn beigleii, are infections of the hair. The skin infections include tinea nigra, caused by Exophiala werneckii, and tinea versicolor, caused by M. furfur. Where the skin is involved, the infections are limited to the outermost layers of the stratum corneum; in the case of hairs, the infection is limited to the cuticle. In general, these infections cause no physical discomfort to the patient, and the disease is brought to the attention of the physician for cosmetic reasons.

Cutaneous mycoses

The cutaneous mycoses are caused by a homogeneous group of keratinophilic fungi termed the dermatophytes. Species within this group are capable of colonizing the integument and its appendages (the hair and the nails). In general, the infections are limited to the nonliving keratinized layers of skin, hair, and nails, but a variety of pathologic changes can occur depending on the etiologic agent, site of infection, and immune status of the host. The diseases are collectively called the dermatophytoses, ringworms, or tineas. They account for most of the fungal infections of humans.

Subcutaneous mycoses

The subcutaneous mycoses include a wide spectrum of infections caused by a heterogeneous group of fungi. The infections are characterized by the development of lesions at sites of inoculation, commonly as a result of traumatic implantation of the etiologic agent. The infections initially involve the deeper layers of the dermis and subcutaneous tissues, but they eventually extend into the epidermis. The lesions usually remain localized or spread slowly by direct extension via the lymphatics, for example, subcutaneous sporotrichosis.

Systemic mycoses

The initial focus of the systemic mycoses is the lung. The vast majority of cases in healthy, immunologically competent individuals are asymptomatic or of short duration and resolve rapidly, accompanied in the host by a high degree of specific resistance. However, in immunosuppressed patients the infection can lead to life-threatening disease. See Fungi, Medical mycology

References in periodicals archive ?
Further analysis revealed that the system the flies use for detecting and defending against fungal infection was deactivated.
Because fungal infections are frequently underrecognized and difficult to detect, one of the largest gaps in our understanding of their epidemiology is determining the incidence of disease.
Among active duty service members receiving an injection with MPA, three (5%) deployed within a period in which they were at risk for a fungal infection; one deployed service member developed a fungal infection after the injection and was medically evacuated.
Amphotericin B exerts broad-spectrum coverage and remains the drug of choice for life-threatening invasive fungal infections.
Reports in the literature state a lower incidence of invasive fungal infections in newborns, perhaps because these studies are compiled from large pediatric databases, Dr.
In situ hybridization has a potential role in distinguishing between organisms of similar morphology in cutaneous fungal infections," the investigators concluded.
Inexpensive, rapid diagnostic tests are available for important fungal infections but are not being widely used.
This leads to fungal infections and other hair problems that can lead to hair fall.
Food and Drug Administration (FDA) has granted orphan drug designation to APX001 and has also designated APX001 as a Qualified Infectious Disease Product (QIDP) for the treatment of multiple fungal infections.
Mucormycosis is a life threatening fungal infection and remains an important cause of morbidity and mortality in immunocompromised patients after hematopoietic stem cell transplant.
Wheat and her associates recommend a single-agent topical antifungal to treat superficial fungal infection.
The variability in presentation makes diagnosing fungal infections especially challenging, he noted.