These growths are related to mushrooms, only they are very much smaller. However, fungi are relatively large organisms compared to bacteria and viruses. There are two forms of fungi:
- unicellular forms – yeasts
- multicellular forms – molds – The green or white mold which forms on stale bread is a tiny fungus.
Fungi are common resident microbes. These organisms frequently inhabit the skin surface or mucous membranes and are kept at bay by intact integument, inflammatory, and immune cells. Resident bacteria also compete with the regulate growth of resident fungi. The reduction of resident bacteria, often via antibiotics, disturbs this balance and allows fungal overgrowth.
Fungal infections can also be opportunistic. Opportunistic pathogens are those that cause disease only in a host with a compromised immune system. Patients with fungal invasion of tissues are frequently immunocompromised, such as persons with AIDS.
- One of the most common opportunistic yeast infections involves Candida. Yeast grows well in warm, moist, dark environments; common sites for superficial candidal epithelial cell infection include those with skin-skin contact, such as beneath the breasts in women, the diaper area in infants, and the perineum, between toes, nail beds, and oral mucosa in susceptible individuals.
- Clinical manifestations of superficial Candida cutaneous invasion include skin redness, itching, and burning at the site. In oral candidiasis, lesions are white and resemble cottage cheese attached to an erythematous oral cavity; these lesions bleed easily and can be painful if scraped. Vulvovaginal candidiasis also produces redness, itching, and burning at the site along with a thick, white, vaginal discharge.