Intro to Mycology

Fungi

-- are eukaryotic so they have a true nucleus and mitochondria. Like plants _______ have a cell wall but it is made of chitin instead of cellulose. They do not possess chlorophyll so they must absorb energy from the environment. They do best with a neutral pH and need moisture to grow.

Fungi Benefits

---Yeast is used in the preparation of foods like yogurt, bread and cheese. ---Molds are used in the production of cheeses and other foods and also serve an antimicrobial purpose. ----Molds can also have a negative impact on our food industry.

Basidiomycota

-Only major pathogen is Filobasidiella neoformans, the perfect (sexual) form of Cryptococcus neoformans var. neoformans.

four groups of fungi in molds

-Zygomycota -Asmycota -Basidiomycota -Fungi Imperfecti

Dimorphic fungi

-exists in both forms of molds and yeasts

Dimorphic Species

Blastomyces dermatitidis, Coccidiodes immitis, Histoplasma capsulatum var. capsulatum, Paracoccidioides brasiliensis, Sporothrix schenckii, and Penicillium marneffei.

Ascomycota

Characterized by the production of sexual spores known as ascospores but usually identified by asexual structures. ----Common examples include: Microsporum spp., Trichophyton spp., and Pseudallescheria boydii.

Fungi Imperfecti

Contains the largest number of organisms that are etiologic agents of infections. Organisms are placed in this group when no mode of sexual reproduction has been identified.

MOisture

Needs___ to grow

Zygomycota

Zygomycetes are rapidly growing organisms normally found in the soil that become opportunistic pathogens. May asexually reproduce creating spores in the sporangium (sproangiospores) or sexually creating zygospores. --Common examples include: Mucor, Rizopus, and Absidia.

Cutaneous mycoses

are infections affecting the keratinized layer of skin, hair or nails. Signs include itching, scaling, or ring-like patches or skin. ---Fungal genera include: Trichophyton, Epidermophyton and Microsporum organisms.

Opportunistic fungal Infections

caused by saprobes are becoming more and more common as we have a more diverse immunocompromised population. --- There are upwards of 24 different species in this category a few examples are: Alternaria spp., Aspergillus spp., Curvularia spp., Fusarium spp., Mucor spp., Penicillium spp., Syncephalastrum spp., and Ulocladium spp.

Superficial mycoses

infections confined to the outermost layer of skin or hair. --Characteristics include discoloration or depigmentation and scaling of the skin. ---Fungal species include: Malassezia furfur, Piedria hortae, and Trichosporon beiglii.

Subcutaneous mycoses

involve deeper skin layers including muscle and connective tissue. --Characteristics include progressive, non-healing ulcers and presence of draining tracts. ---Tropical areas have species Phialophora spp. and Cladosporium spp. Sporothrix schenckii may present in a cutaneous form and disseminate into a systemic infection.

Yeast or tissue state

is seen in vivo (life, in patient) or when grown at 37°C

Chitin

made of fungi cell wall

Molds

multicellular, filamentous fungi that have a fuzzy or woolly appearance due to the mycelium. Mycelium is made up of many long strands of tube-like structures called hyphae which may be aerial or vegetative. -______ are often identified by microscopic observation so the details of their structures are of note. --Hyphae may be septate or sparsely septate, indicating how often there is a cross-wall between cells. ---- Hyphae are often either hyaline, lightly pigmented, or dematiaceous or darkly pigmented due to melanin in the cell wall. -----May produce sexually or asexually

Mold sexual reproduction

requires the joining of two compatible nuclei followed by meiosis.

Mold asexual reproduction

results in the formation of conidia after mitosis by budding from the conidiogenous cells (specialized cells). Asexual reproduction can also be carried out by forming arthroconidia by fragmentation of fertile hyphae. In the clinical lab most molds are identified on the basis of the structures formed as a result of asexual reproduction.

Mold Phase

seen when the organism is grown at room temperature or 25°C.

Mycology

the study of fungi and fungi are very diverse but generally classified as either yeast or mold.

Systemic mycoses

those infections that affect internal organs or deep tissues of the body. The initial site is often the lung where the organism may disseminate via the circulatory system. ----General symptoms are fever and fatigue or chronic cough and chest pain. ----- Diamorphic species include: Histoplasma, Coccidioides, and Bastomyces.

yeasts

unicellular, nucleated rounded fungi; reproduce by a process called budding with production of a blastoconidium or daughter cell. -____ produce creamy bacteria-like colony without aerial hyphae. ---differentiated by colony appearance, microscopic stains and carbohydrate assimilation. --------The most clinically significant _____ are Candida albicans and Cryptococcus neoformans.