What Are Fungal Fimbriae

BiofilmsAdhesions: Example – Adhesions are bands of scar-like tissue. Normally, internal tissues and organs have slippery surfaces so they can shift easily as the body moves. Adhesions cause tissues and organs to stick together. Example: They might connect the loops of the intestines to each other, to nearby organs, or to the wall of the abdomen.

Fungal fimbriae are surface appendages that were first described on the haploid cells of the smut fungus, Microbotryum violaceum. They are long (1-20 gm), narrow (7 nm) flexuous structures that have been implicated in cellular functions such as mating and pathogenesis. Since the initial description, numerous fungi from all five phyla have been shown to produce fimbriae on their extracellular surfaces.

Cell-to-cell interactions are fundamental to the processes of fungal growth and development. In particular, cell-to-cell adhesions occur during mating and pathogenesis.

Many fungi produce flexible, long (1-20 ,um), narrow (7 nm), unbranched appendages which appear similar to pili or fimbriae found on the surface of prokaryotic cells. These structures, termed fungal fimbriae, were first observed on the surface of haploid yeast-like cells of the anther smut Microbotryum violaceum (= Ustilago violacea) by Poon and Day (1974). Since their original description, fungal fimbriae have been shown to be widespread among the Mycota (Gardiner et al., 1981, 1982; Benhamou and Ouellette, 1987; Castle et al., 1992; Rghei et al., 1992; Celerin et al., 1995).

In M.violaceum, fungal fimbriae appear to be involved in cell-to-cell communication during mating before pathogenesis. Both mechanical and enzymatic removal of fimbriae from the haploid cells delays mating until fimbrial regeneration occurs (Poon and Day, 1975). In addition, mating is almost completely blocked by coating fimbriae with anti-fimbrial protein antiserum (Castle et al., 1996).

Fungal fimbriae have also been implicated as factors involved in pathogenic adhesion. Rghei et al. (1992) suggested that fimbriae are used in the initial interactions between a parasitic fungus and its host.

PDF: Fungal fimbriae are composed of collagen

Read about Filamentous Biofilm.

Fungi and Human Pathogenesis

~ Content Source – Neal Chamberlain

Humans have a high level of innate immunity to fungi and most of the infections they cause are mild and self-limiting.

This resistance is due to:

  • 1. the fatty acid content of the skin.
  • 2. the pH of the skin, mucosal surfaces and body fluids.
  • 3. Epithelial cell turnover.
  • 4. Normal flora.
  • 5. Transferrin.
  • 6. Cilia of the respiratory tract.

When fungi do pass the resistance barriers of the human body and establish infections, the infections are classified according to the tissue levels initially colonized.

A. Superficial mycoses– infections limited to the outermost layers of the skin and hair.

B. Cutaneous mycoses– infections that extend deeper into the epidermis, as well as invasive hair and nail diseases.

These diseases are restricted to the keritinized layers of the skin, hair, and nails. Unlike the superficial mycoses, host immune responses may be evoked, resulting in pathologic changes expressed in the deeper layers of the skin. The organisms that cause these diseases are called dermatophytes. These diseases are often called ringworm or tinea. All the following diseases are causes by MicrosporumTrichophytonand Epidermophytonwhich comprise 41 species.

C. Subcutaneous mycoses- infections involve the dermis, subcutaneous tissues, muscle, and fascia. These infections are chronic and are initiated by trauma to the skin. These infections are difficult to treat and may require surgical intervention.

D. Systemic mycoses- infections that originate primarily in the lungs and may spread to many organ systems. These organisms are inherently virulent. All but Cryptococcus are dimorphic fungi.

Histoplasma capsulatum– Ohio and Mississippi river valleys, Yeast cells in tissue, Tuberculate macroconidia in mycelial phase.

Blastomyces dermatitidis– Ohio and Mississippi river valleys, Broad Base Budding yeast in tissue, Mycelia= microconidia

Coccidioides immitis– Southwestern US. Spherule in tissue, barrel-shaped Arthroconidia in mycelia phase.

Cryptococcus neoformans– Only yeast phase but unusual in that the cells are encapsulated as demonstrated by an India Ink stain.

E. Opportunistic mycoses– infections of patients with immune deficiencies who would otherwise not be infected. Ex. AIDS, altered normal flora, diabetes mellitus, immunosuppressive therapy, malignancy.

Candidiasis– Candida albicans– Creamy growth on various body surfaces. ex. mouth, skin, vagina. Budding yeast. Form pseudohyphae in tissue. Germ tube when grown in serum.

Aspergillosis– Aspergillus niger.

For more content download PDF Doc – Fungal Infections