Mycology Mycology - the study of fungi Fungi - includes molds and yeasts. Molds - exhibit filamentous type of growth. Yeasts - exhibit pasty or mucoid form of fungal growth. • 50,000 + valid species • Fungi stain gram positive, and require oxygen to survive. • Fungi are eukaryotic, containing a nucleus bound by a membrane, an endoplasmic reticulum, and mitochondria. (Bacteria are prokaryotes and do not contain these) • Fungi are heterotrophic like animals and most bacteria; requiring organic nutrients as a source of energy. (Plants are autotrophic)
Mycology Fungi are dependent upon enzyme systems to derive energy from organic substrates. • Saprophytes - live on dead organic matter. • parasites - live on living organisms. Fungi are essential in recycling of elements, especially carbon.
Mycology Role of fungi in the economy: Industrial uses of fungi - • Mushrooms. (Class Basidiomycetes) • Truffles. (Class Ascomycetes) • Natural food supply for wild animals. • Yeast as food supplement, supplies vitamins. • Penicillium - ripens cheese, adds flavor (roquefort, etc.). • Fungi used to alter texture, improve flavor of natural and processed foods.
Mycology Fermentation • Fruit juices (ethyl alcohol). • Saccharomyces cerevisiae - brewer's and baker's yeast. • Fermentation of industrial alcohol, fats, proteins, acids, etc. Antibiotics - • First observed by Fleming; noted suppression of bacteria by a contaminating fungus of a culture plate.
Mycology Plant pathology - • Most plant diseases are caused by fungi. Medical importance - • 50-100 species are recognized human pathogens. • Most prefer to be free-living saprophytes; and only accidentally become pathogens. • To be pathogenic, they must tolerate the temperature of the host site and possess an enzymatic system that allows them to utilitize animal tissues. • Increased incidence of fungal infections in recent times.
Mycology Importance of Medical Mycology • During the time period between 1941 - 1973, the number of reported deaths in the U.S. due to scarlet fever, typhoid, whooping cough, diphtheria, dysentery and malaria decreased from 10,165 cases to 107; but reported deaths due to mycoses during the same time period, increased from 324 to 530. • Increased mobility - We can travel to a geographical area where a fungus exists as part of the commensal flora of the local population, or is endemic to the area. • We have an aging population.
Mycology The Immunosuppressed Patient: • AIDS • Drugs - immunosuppressant drugs used in organ transplant patients, cancer and leukemia patients.
Mycology Immunology of the Mycoses Antibody mediated immunity (B-cell, humoral) • Antibodies are often produced in response to a fungal infection, but do not confer immunity. • Serological tests for identification of fungal diseases detect these antibodies. Cellular mediated immunity (T-cell) • T-cell immunity is effective in resistance to fungal infections.
Mycology Basic terms as they relate to mycology: • Hypha (hyphae plural) - fundamental tube-like structural units of fungi. • Septate - divided by cross walls. • Aseptate - lacking cross walls. • Mycelium - a mass (mat) of hyphae forming the vegetative portion of the fungus. • Aerial - growing or existing in the air. • Vegetative - absorbs nutrients. • Fertile - bears conidia (spores) for reproduction.
Mycology Basic Terms (continued) Sporulation & Spores - preferred terms when there is a merging of nuclear material. Self-fertile are termed homothallic. Mating types are termed heterothallic. • Sexual spores - exhibit fusion of nuclei. • Ascospore - spore formed in a sac-like cell known as an ascus. Often eight (8) spores formed. (Ascomycetes) • Basidiospore - sexual spore produced on a specialized club-shaped structure, called a basidium. (Basidiomycetes) • Zygospore - a thick-walled spore formed during sexual reproduction (Phycomycetes)
Mycology Sporulation & Spores (continued) • Asexual spores - most common type. • Conidia - asexual fungal spores borne externally in various ways from a conidiophore; often referred to a macroconidia (multicellular) and microconidia (unicellular). • Arthroconidium (Arthrospore) - special type of asexual spore formed by disarticulation of the mycelium. • Blastoconidia (Blastospore) - asexual spore formed from a budding process along the mycelium or from another blastospore.
Mycology • Asexual Spores (continued) • Chlamydospore - thick-walled asexual spore formed by direct differentiation of the mycelium (concentration of protoplasm and nutrients). • Sporangiospore - an asexual spore contained in a sporangium at the end of a sporangoiphore. • Thallospore - asexual spore produced on a thallus (hypha).
Mycology Miscellanous terms: • Ascus - sac-like structure containing (usually eight) ascospores developed during sexual reproduction in the Ascomycetes. • Conidiophore - a specialized branch of hypha on which conidia are developed. • Dematiaceous - pigmented, dark in color, usually gray to black. • Hyaline - colorless, clear. • Dermatophyte - fungus that causes superficial mycoses.
Mycology Miscellanous terms: (continued) • Diphasic (dimorphic) - the ability of some fungi to grow as either yeast or filamentous stages, depending on conditions. • Ectothrixic - ability of the fungus to grow on the outside of a hair shaft. • Endothrixic - ability of the fungus to grow and penetrate into the hair shaft. • Germ Tube - small projections which arise from cells of certain yeasts; indicates the onset of hyphal formation.
Mycology Miscellanous terms: (continued) • Pseudohyphae - a chain of elongated budding cells that have failed to detach (not true hyphae). • Rhizoids - root-like structures. • Sporangiophore - a special aerial hypha or stalk bearing a sporangium. • Sporangium - a sac or cell containing spores produced asexually. • Sterigmata - a specialized structure that arises from a basidium and supports basidiospores.
Mycology Classifications of Fungi: • Geographic grouping - where they exist. • Epidemiologic grouping - how organism is transmitted. • Taxonomy grouping - according to morphologic and cultural characteristics. • Topographic Grouping - type of mycosis produced.
Mycology Topographic Grouping of Fungi: (most often used) • Superficial - Confined to the outermost layers of the skin and hair.No host cellular or inflammatory response due to organisms being remote from living tissue. Essentially no pathology; the disease is recognized purely on cosmetic basis. • Cutaneous - in the keratin of the skin, nails, and hair. These organisms prefer non-living cornified layers. The disease is called a dermatophytosis or dermatomycosis. Host response is patchy scaling or eczema eruptions. They are classified according to the area of the body that is involved.
Mycology Topographic Grouping of Fungi: (continued) • Subcutaneous - Involve the deeper layers of skin and often muscle tissue.Man is an accidental host following inoculation of fungal spores via some form of trauma. This type of infection is often identified by the presence of a characteristic tissue reaction or granule. • Systemic - Attack the deep tissues and organ systems; often creating symptoms that resemble other diseases.
Mycology Categories of systemic disease: • Those caused by truly pathogenic fungi with the ability to cause disease in the normal human host when the inoculum is of sufficient size (Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides immitis, Paracoccidioides braziliensis). • Those caused by opportunistic fungi, low virulence organisms, which require the patient's defenses to be lowered before the infection is established (Aspergillus spp. Candida albicans, Cryptococcus neoformans).
Mycology Saprophytes: • Contaminates or opportunistic pathogens? • Most are inhibited by cycloheximide. • Grouped by type of mycelia produced. • Septate vs. aseptate • Hyaline vs. dematiaceous
Mycology Saprophytes: Hyaline Members - Aspergillus spp. • Growth rate varies, colors vary, surface velvety to cottony. • Mycelium - septate and hyaline with unbranched condiophores (compare to Syncephalastrum, which appears similar, but is aseptate). • A. fumigatus is considered a potential pathogen, especially if from a pulmonary source.
Mycology Saprophytes: Hyaline Members - Paecilomyces spp. • Rapid grower, colors vary. • Brush-like conidiophores. • Long, tapered sterigmata.
Mycology Saprophytes: Hyaline Members - Penicillium spp. • Commonly rapid growing; white to bluish-green. • Conidiophores characteristically form a brush-shaped structure. • Sterigmata are flask shaped.
Mycology Saprophytes: Hyaline Members - Scopulariopsis spp. • Moderately slow growing. White turning brown with age. • Branched or unbranched conidiophores. • Sterigmata are coarsely roughened.
Mycology Saprophytes: Hyaline Members - Trichoderma spp. • Moderately rapid growth. • Flask-shaped conidiophores. • Conidia are clustered.
Mycology Saprophytes: Hyaline Members - Fusarium spp. • Rapid growth, white colonies may be come brightly colored. • Short conidiophores often branched, have macro- and micro-conidia, which are oval to sickle-shaped. • Has been reported to cause eye infections.
Mycology Saprophytes: Dematiaceous Members - Alternaria spp. • Rapid growth; colonies become very dark with age; may become overgrown with looser white to gray aerial mycelium. • Conidiophores bear single or branched chains of large, brown conidia.
Mycology Saprophytes: Dematiaceous Members - Curvalaria spp. • Rapid growth. Velvety colonies vary in color from grayish-brown to black. • Spirally arranged brown conidia are borne at the tips. • Brown, septate, unbranched conidiophores.
Mycology Saprophytes: Dematiaceous Members - Cladosporium spp. • Rapid growth. Green colonies, reverse is black. • Septate, dematiaceous mycelium. • Conidia are borne in chains.
Mycology Saprophytes: Aseptate Members - • All are susceptible to cycloheximide. • Rapid growers. • Some have root-like structures termed rhizoids. • Spore bearing structures are called sporangiophores.
Mycology Saprophytes: Aseptate Members - Mucor spp. • Very rapid growth; can fill a culture tube in one day. • Unbranched sporangiophores. • No rhizoids
Mycology Saprophytes: Aseptate Members - Rhizopus spp. • Rhizoids are present. • Sporangiophores nodal in origin.
Mycology Saprophytes: Aseptate Members - Syncephalastrum spp. • Very rapid growth. White to dark gray colonies with dense, cottony, aerial mycelium. • Aseptate, hyaline mycelium, with short, branched sporangiophores, terminating into tips. • Many tubular sporangia containing chains of spores.
Mycology Yeasts: Candidia albicans • Cutaneous infections such as oral thrush or vaginitis, but can become systemic. • ID by positive germ tube test, or production of chlamydospore on cornmeal agar.
Mycology Yeasts: Cryptococcus neoformans • Associated with pigeon feces. • Has thick capsule. • Grows at 37 degrees & produces melanin-like pigment on caffeic acid agar. • ID in CSF by India ink stain for capsule.
Mycology Yeasts: Geotrichumspp. • Commonly present in GI tract. • Implicated in respiratory infections; frequently as a secondary invader. • Causes disease in the immunosuppressed. • Produces arthrospores.
Mycology Bacteria - Like Fungi: • Some produce sulfur granules (Actinomyces israeli) • Often require special media, stains, & conditions for growth, i.e. anaerobic (Actinomycetes spp). • Some are partially acid-fast (Nocardia spp.)
Mycology Dimorphic Fungi: Sporothrix schenkii • Rose fever, gardeners often affected. • Infection via traumatic implantation.
Mycology Dimorphic Fungi: Coccidioides immitis • San Joaquin valley fever. • Mycelial phase present in culture. • Yeast phase in tissue.
Mycology Dimorphic Fungi: Histoplasma capsulatum • Mississippi Valley fever. • Associated with bird droppings. • Disease mimics tuberculosis. • Found frequently in reticuloendothelial cells as extracellular inclusions. H. capsulatum mold phase H. capsulatum yeast phase
Mycology Dimorphic Fungi: Blastomyces dermatitis • North American Blastomycosis(Gilcrest disease). • Large yeast cells with single bud.
Mycology Dimorphic Fungi: Paracoccidioides braziliensis • South American Blastomycosis. • Large yeast cells with multiple buds (mariner’s wheel).
Mycology Superficial mycoses: Malassezia furfur • Cause of pityriasis versicolor (tinea versicolor). Phaeoannellomyces werneckii • Cause of superficial phaeohyphomycosis (tinea nigra).
Mycology Superficial mycoses: Trichosporon beigelii • Cause of white piedra. Piedraia hortae • Cause of black piedra.
Mycology Cutaneous mycoses: Microsporum spp. - in hair, skin, rarely nails; frequently in children, rarely in adults; often spontaneous remission occurs (ringworm). Trichophyton spp. - hair, skin & nails; in both children & adults (athlete’s foot). Epidermophyton spp. - skin, nails, rarely hair; in adults, rarely in children (ringworm).
Mycology Cutaneous mycoses: Microsporum spp. • Macroconidia are attached singly. • Thick walled. • Mature forms are echinulate (spiny).
Mycology Cutaneous mycoses: Trichophyton spp. • Macroconidia are attached singly. • Have smooth walls.
Mycology Cutaneous mycoses: Epidermophyton spp. • Macroconidia are attached in multiples. • Smooth walls (beaver tails). • Grows slowly.
Mycology Subcutaneous mycoses: Chronic, supperative or granulomatous infections of the subcutaneous tissues, usually on an extremity (hands, feet); can extend through the lymphatics or form sinus tracts. Caused by a variety of fungi and bacteria-like fungi that live in the soil. Chromoblastomycosis: • Non-contagious skin diseases characterized by the development of a warty lesion that has a cauliflower appearance. Occurrence is usually on the legs or feet. Caused by Fonsecaea pedrosoi, Cladosporium spp., and Phialophora spp. Fonsecaea pedrosoi is the most common etiologic agent of chromoblastomycosis worldwide.
Mycology Subcutaneous mycoses: Mycetoma: • Localized, tumorous lesions in cutaneous and subcutaneous tissues usually the foot. Nodules are formed, and a collection of pus and formation of sinuses results. • Actinomycotic mycetomas must be differentiated from Eumycotic (true fungi) mycetomas and as they have greatly differing treatments.