Characterizing and Classifying Fungus Chapter 12 Characterizing and Classifying Fungus

Mycology: The Study of Fungi

Appearance of Fungi Yeast – unicellular grow at 37oC Mold – Microscopic Macroscopic Yeast – unicellular grow at 37oC Mold – multicellular grow at 25oC

Dimorphic nature of true fungal pathogens Figure 22.2

Yeasts Round to oval shape; 5-10X larger than bacteria Reproduce by budding, form a blastospore Figure 12.3

Molds Composed of hyphae - multicellular branching filaments - mass of hypae = mycelium Hyphae are septate (with crosswalls) or nonseptate (coenocytic)

Molds Hyphae are vegetative or aerial Reproduce by sexual and asexual sporulation Figure 12.2

Classification by Sexual Sporulation Zygomycete- produce Zygospores examples: Rhizopus (bread mold) Ascomycete – produce Ascospores examples: Penicillium, Saccharomyces Basidiomycete – produce Basidiospores examples: mushrooms, Cryptococcus Deuteromycete (anamorphs)– asexual spores examples: Stachybotrys, Pneumocystis rRNA analysis revealed that most deuteromycetes belong in the division Ascomycota

Zygomycete Life Cycle Figure 12.6

Ascomycete Life Cycle Figure 12.7

Basidiomycete Life Cycle Figure 12.8

Asexual sporulation by mitosis Three basic types of asexual spores: Sporangiospores - form in sac called sporangium Conidiospores – no sac; form at tip or side of hyphae Chlamydospore – thickened cell wall inside hyphae Spore type is used in medical labs to identify pathogenic fungi

Representative asexual spores of molds Figure 12.18

Representative asexual spores of molds

Benefits of Fungus Major role in decomposition Major role as producers of: antibiotics alcohols organic acids vitamins foods: blue cheese, soy sauce, breads

Medical Mycology Medical mycology- Diagnosis, management, and prevention of mycoses (fungal diseases) Mycoses among the most difficult diseases to diagnose and treat Signs of mycoses are often missed or misinterpreted Fungi are often resistant to antifungal agents

Epidemiology of Mycoses Fungi and their spores are almost everywhere in the environment most people will experience a fungal infection at some time Typically acquired via inhalation, trauma, or ingestion Most mycoses are not contagious Dermatophytes, fungi found on the skin, are the major exception

Classification of Fungal Diseases Systemic mycoses Deep within body Subcutaneous mycoses Beneath the skin Cutaneous mycoses Affect hair, skin, nails (Dermatophytosis) Superficial mycoses Localized on outermost skin layers /hair shaft Opportunistic mycoses Caused by normal microbiota or fungi that are normally nonpathogenic

Systemic Mycoses Caused by True Pathogenic Fungi Acquired through inhalation Begin as a generalized pulmonary infection that disseminates via the blood to the rest of the body Have the ability to actively attack and invade tissues Exhibit dimorphism Endemic to certain regions, primarily in the Americas

Systemic Mycoses Caused by True Pathogenic Fungi Coccidioidomycosis (San Juaquin Valley Fever) Caused by Coccidioides immitis Histoplasmosis (Ohio Valley Fever) Caused by Histoplasma capsulatum Blastomycosis (North American Blastomycosis) Caused by Blastomyces dermatitidis Paracoccidomycosis (South American Blastomycosis) Caused by Paracoccidioides brasiliensis

San Joaquin Valley Fever Coccicioides immitis

Coccidioidomycosis- San Joaquin Valley Fever Epidemiology thrives in areas with sandy alkaline soils, very high temperatures, low rainfall, and low elevation Symptoms Most often result in pulmonary conditions Many patients show no or few symptoms but some may develop severe or chronic pulmonary disease Dissemination to other sites occurs mostly in immunocompromised individuals Treatment Infections in healthy individuals resolve on their and require no treatment Amphotericin B is the preferred drug for those who require treatment

Coccidioidomycosis Subcutaneous tissue lesions due to dissemination from the lungs http://botit.botany.wisc.edu/toms_fungi/jan2002.html Figure 22.4 Spherules in lung tissue Figure 22.5

Histoplasmosis – Ohio Valley Fever Epidemiology Found mostly in the eastern United States but also in Africa and Asia Fungi found in moist soils containing high levels of nitrogen from bat and bird droppings Route of infection Inhalation of spores into the lungs is the most common H. capsulatum first attacks alveolar macrophages and is then dispersed beyond the lungs via the blood and lymph Usually asymptomatic and resolve without damage Treatment Amphotericin B is preferred drug if required

Histoplasma capsulatum

Blastomycosis Epidemiology Route of Transmission Symptoms Endemic in the southeastern United States north to Canada Fungi found in soils rich in organic matter Route of Transmission Inhalation of dust can carry fungal spores or hyphal pieces into the lungs Symptoms Pulmonary blastomycosis is the most common manifestation in humans Initial pulmonary lesions are mostly asymptomatic and symptoms, when they develop, are often vague; resolves in most people but in others it may be chronic

Blastomyces dermatitidis Yeast in lung Mold in soil Cutaneous Blastomycosis

Paracoccidioidomycosis Epidemiology Found in southern Mexico and regions of South America Relatively rare disease found most in farm workers in endemic areas Symptoms Similar to blastomycosis and coccidiodomycosis Infection begins as a pulmonary condition Dissemination almost always follows Produces a chronic inflammatory disease of mucous membranes- gums, lips, tongue Treatment Amphotericin B or Ketoconazole

Paracoccidiodes brasiliensis Figure 22.8 Characteristic “steering wheel” formation seen in tissue samples Ulcerative lesions on mucous membranes Figure 22.7

Subcutaneous Mycoses Characteristics Fungi are commonly found in the soil Infections are rare Requires traumatic introduction of the fungal elements beneath the outer, dead layers of skin Most lesions remain localized to the subepidermal tissues in the skin Example: Sporotrichosis (Rose thorn disease)

Subcutaneous Mycoses Sporotrichosis (Rose thorn disease) Sporothrix schenckii is the causative agent Subcutaneous infection usually limited to the arms and legs Those who work with plant material at highest risk for infection Cutaneous sporotrichosis Produces nodular lesions around the infection site Lymphocutaneous sporotrichosis Secondary lesions occur on the skin along the course of lymphatic vessels Effectively treated with topical agents

Sporotrichosis – Rose thorn disease Rose thorn disease or Gardener’s disease Sporothrix schenkii Mold Yeast

Cutaneous Mycosis- Dermatophytoses Dermatophytes Caused by Trichophyton, Epidermophyton, Microsporum Ringworm or “Tinea” Fungal infections of the skin hair, nails Result from fungi that use keratin as a nutrient source and thus colonize only dead tissues Symptoms Infections were previously called ringworm because they resemble a worm lying below the surface of the skin Can provoke cell-mediated immune response that damages living tissues http://www.emedicinehealth.com/slideshow_ringworm_pictures/article_em.htm

Common Dermatophytoses Tinea pedis “Athletes foot” Tinea cruris “Jock itch” Tinea corporis “Ringworm”

Superficial mycoses – Pityriasis versicolor Fungi interfere with melanin production Characterized by depigmented or hyperpigmented patches of scaly skin Relapses are common Malassezia furfur Causative agent fluoresces pale green providing a rapid diagnostic method Grows in oil

Factors that Predispose Individuals to Opportunistic Mycoses Table 22.1

Opportunistic Mycoses Usually limited to people with poor immunity Immunocompromised individuals Mycoses account for most deaths associated with AIDS and used to define end-stage disease Can be difficult to identify because their symptoms are often atypical Opportunisitic mycoses: Candidiasis –Localized infections in mouth (thrush), vagina, skin. Systemic in HIV infections. Pneumocystis pneumonia (PCP) - HIV associated pneumonia. Rare prior to AIDS epidemic Cryptococcoses – causes meningitis when fungus spreads to CNS. Systemic in HIV infections Aspergillosis – causes pulmonary disease; allergies

Candidiasis Candida albicans - most common causative agent Yeast Normal flora of skin and mucous membranes Can be transmitted between individuals Always an opportunist infection producing wide range of diseases

Thrush - Oropharyngeal Candidiasis Candidiasis Clinical Manifestations Diaper Rash Thrush - Oropharyngeal Candidiasis Onychomycosis Ocular candidiasis Figure 22.10 - Overview

Cryptococcosis Cryptococcus neoformans Yeast Resists phagocytosis by producing capsules Has affinity for the central nervous system where blood/brain barrier protects it from immune response Route of Transmission Infections can result from the inhalation of airborne spores found in bird droppings Negative stain of Encapsulated yeast in cerebral spinal fluid

Cryptococcosis Cryptococcal meningitis Most common clinical form of cryptococcal infection Follows dissemination of the fungus to the CNS Symptoms: headache, stiff neck, nausea, photophobia, hallucinations, fever Primary pulmonary cryptococcosis Asymptomatic or mild pneumonia Invasive cryptococcosis sometimes occurs, resulting in chronic pneumonia Cutaneous cryptococcosis Skin lesions or inflamed subcutaneous

Aspergillosis Due to Aspergillus fumigatus and other species Clinical Manifestations Hypersensitivity aspergillosis Manifests as asthma or other allergic symptoms Noninvasive aspergillomas (mycetoma) Masses of fungal hyphae form in the cavities after a case of pulmonary tuberculosis Acute invasive pulmonary aspergillosis May present as mild pneumonia Necrosis of lung tissue can lead to significant respiratory impairment Nonpulmonary diseases can also result Includes cutaneous and systemic aspergillosis

Mycetoma caused by Aspergillus

Fungal Intoxications and Allergies Some fungi cause allergies Fungal allergens can elicit a hypersensitivity response in sensitive individuals seen as hay fever or eczema Result from inhalation, ingestion, or other contact Sick Building Syndrome caused by Stachybotrys http://www.cdc.gov/mold/stachy.htm Some fungi produce toxins Mycotoxicosis Caused by eating foods contaminated with fungal toxins Mycetismus Mushroom poisoning from eating a fungus

Mycotoxicoses- Fungal Toxins Mycotoxins normal byproducts of metabolic activities but are poisonous to animals and humans Aflatoxins –produced by Aspergillus flavus consumed in contaminated food crops; prevalent in the tropics can cause liver and kidney damage, gastrointestinal or gynecological disturbances, or cancers carcinogenic at low levels when consumed continually Ergot alkaloids- used to make drugs Ergotamine – treatment for migraine headaches Ergometrine – constricts blood vessels; stimulates labor contractions

Mold on food Yeah, but…Can I cut off the moldy part of the cheese (or bread) and eat the rest? http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/safe-food-handling/molds-on-food-are-they-dangerous

Mycetismus- Fungal Toxins Mushroom Poisoning Most mushrooms are not toxic Poisonous varieties called toadstools Poisons cause neurological dysfunction or hallucinations, organ damage, or even death Amanita phalloides - “death cap” mushroom; produces deadliest mushroom toxin

Psilocybin mushrooms – Have psychoactive compound causing hallucinations “shrooming”