Fungal Infections

FUNGAL INFECTIONS

Fungal infections are divided into superficial or deepseated infections. Superficial infections affect the skin, nails or mucosal surfaces of the mouth or genital tract. In contrast, deep-seated fungal diseases may target the lung or disseminate via the bloodstream to organs such as the brain, spleen, liver or skeletal system.

The fungal infections of the skin and nails include tinea pedis (athlete’s foot), tinea capitis and tinea corporis (ringworm), Candida intertrigo (usually groin and sub-mammary regions) and pityriasis (Malassezia). A variety of topical and systemic antifungal agents are available. The imidazole class of drugs includes clotrimazole and miconazole, which are highly effective topically. Systemic antifungals used to treat superficial fungal infections include griseofulvin and terbinafine, which is an allylamine. Both agents are ineffective in the treatment of deep-seated fungal infections that may be caused by yeasts (Cryptococcus neoformans), yeast-like fungi (Candida spp.) or the filamentous fungi (Aspergillus spp). These produce a variety of syndromes for which different antifungal agents are indicated (Table 14.5). The polyenes include amphotericin B, which after many years remains the agent of choice for the treatment of a wide variety of life-threatening fungal diseases which often complicate cancer chemotherapy, organ transplantation and immunodeficiency diseases, such as AIDS. Nephrotoxicity is common but can be avoided by careful dosaging or the use of liposomal formulations. The second major class of systemic antifungals is the triazoles, which include fluconazole and newer, broader-spectrum agents such as itraconazole, voriconazole and posaconazole. These are extremely well tolerated but may interact with a number of drugs and drug classes such as the sulphonylureas, antihistamines and lipid-lowering agents among others. The echinocandins (caspofungin, anidulafungin) are the newest class of antifungal agents, and are increasingly used to treat invasive fungal infections; they have a fungicidal action against Candida spp., and are fungistatic against many other organisms, including Aspergillus spp.