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58 Cards in this Set
- Front
- Back
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What is the definition of yeast?
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Unicellular growth form of fungi.
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How do yeast reproduce?
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Yeast reproduce by budding.
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What are pseudohyphae?
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When buds do not separate, they can form long chains of yeast cells, which are called pseudohyphae.
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Which reproduces at a faster rate: bacteria or yeast?
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Bacteria
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Hyphae
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Threadlike, branching, cylindrical, tubules composed of fungal cells attached end to end. These grow by extending in length from the tips of the tubules.
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Molds are also called _____. What are they?
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Mycelia
They are multicellular colonies composed of clumps of intertwined branching hyphae. Molds grow by longitudinal extension and produce spores. |
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Spores
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The reproducing bodies of molds.
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Dimorphic fungi
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Fungi that can grow as either a yeast or mold, depending on environmental conditions and temperature.
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Saprophytes
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Fungi that live in and utilize organic matter (soil, rotten vegetation) as an energy source.
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The fungal cell membrane is the __(a)__-most layer around the fungal cytoplasm. It contains __(b)__, which are also found in the cell membranes of humans. The essential sterol in fungi is __(c)__.
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a. inner
b. sterols c. ergosterol |
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The majority of antifungal agents work by disrupting __(a)__, either by binding to it and thereby __(b)__ in the cell wall, or by interfering with __(c)__ synthesis.
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a. ergosterol
b. punching holes c. ergosterol |
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Fungus cell wall surrounds the __(a)__, and is composed mostly of __(b)__, with some __(c)__. They are potent __(d)__ to the human immune system.
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a. cell membrane
b. carbohydrates c. protein d. antigens |
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The fungus capsule is a __(a)__ coating that surrounds the __(b)__. It is an __(c)__ virulence factor.
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a. polysaccharide
b. cell wall c. antiphagocytic |
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Two superficial fungal infections:
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1. pityriasis versicolor
2. tinea nigra |
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What are the primary manifestations of the superficial fungal infections?
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Pigment change of the skin.
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Pityriasis versicolor:
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Chronic superficial fungal infection that leads to hypo-pigmented or hyper-pigmented patches on the skin. With sunlight exposure the skin around the patches will tan, but the patches will remain white.
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What is the causative agent of pityriasis versicolor?
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Malassezia furfur
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Tinea nigra:
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Superficial fungal infxn that causes dark brown to black painless patches on the soles of the hands and feet.
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What is the causative agent of tinea nigra?
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Exophiala werneckii
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Diagnosis of the superficial fungal infections is based on what?
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Microscopic examination of skin scrapings, mixed on a slide with KOH. Malassezia can look like spaghetti (hyphae) with meatballs (spherical yeast).
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What is the treatment for pityriasis versicolor and tinea nigra?
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Spreading dandruff shampoo containing selenium sulfide over the skin.
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Dermatophytoses cause infections where?
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Cutaneous infxns of the skin, hair, and nails.
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Dermatophytoses secrete an enzyme called:
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keratinase
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The common dermatophytes include (3):
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1. microsporum
2. trichophyton 3. epidermophyton |
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Tinea corporis
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ring worm - invasion of horny layer of skin
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Tinea cruris
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jock itch
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Tinea pedis
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athlete's foot
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Tinea capitis
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scalp - resulting in scaly red lesions with loss of hair - normally occurs in children
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Tinea unguium
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nails - will be thickened, discolored, and brittle
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How to diagnose a dermatophyte infection?
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1. Dissolve skin scrapings in KOH, which will digest the keratin. Should then see branched hyphae.
2. Direct examination with Wood's light (UV light) - certain species will fluoresce brightly. |
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Treatment of dermatophytoses:
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Topical imidazoles
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Candida albicans
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Causes cutaneous fungal infections in mouth, groin, and vagina. It can also cause opportunistic systemic infections.
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How do subcutaneous fungal infections gain entrance to the body?
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Following trauma to the skin.
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Do subcutaneous fungal infections spread?
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They usually remain localized to the subcutaneous tissue or spread along lymphatics to local nodes.
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Sporothrix schenkii
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-dimorphic
-commonly found in soil and on plants |
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What disease is caused by sporothrix schenckii?
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Sporotrichosis
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Sporotrichosis
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Following infection, a subcutaneous nodule gradually appears, which becomes necrotic and ulcerates. The ulcer heals, but new nodules pop up nearby and along the lymphatic tracts up the arm.
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Phialophora and Cladosporium
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Copper-colored soil saprophytes found on rotting wood.
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What disease do phialophora and cladosporium cause?
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Chromoblastomycosis
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Chromoblastomycosis:
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Infection occurs following a puncture would. First, a small, violet wart-like lesion develops. Over months to years, additional lesions arise nearby. Clusters of these lesions resemble cauliflower.
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How to treat chromoblastomycosis:
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Itraconazole and local excision
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Three fungi that cause systemic disease in humans:
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1. Histoplasma capsulatum
2. Blastomyces dermatitidis 3. Coccidioides immitis |
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The three fungi that cause systemic disease are _(a)_-morphic, and grow as _(b)_forms, with _(c)_, at 25 C. At 37 C, they grow in a _(d)_ form.
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a. di
b. mycelial c. spores d. yeast |
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How does the dimorphism of the systemic fungi play a part in human infection?
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In their natural habitat (the soil) they grow as mycelia and release spores into the air. These spores are inhaled by humans and at the human temp of 37 C, they grow as yeast cells.
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The three systemic fungi have three clinical presentations:
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1. Asymptomatic: majority
2. Pneumonia: a mild pneumonia can develop with fever, cough, and chest x-ray infiltrates. 3. Disseminated: Rarely, hematogenous spread can cause disseminated disease, such as meningitis, bone lytic granulomas, skin granulomas. Usually in immunocompromised host. |
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Can the systemic fungi be transmitted person to person?
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No.
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Cryptococcus neoformans is a __(a)__ encapsulated yeast that's not __(b)__. It's similar to the three systemic fungi in that it's __(c)__ into the lungs and infection is usually __(d)__. It differs in that the major manifestation is not pneumonia but rather __(e)__.
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a. polysaccharide
b. dimorphic c. inhaled d. asymptomatic e. meningoencephalitis |
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Where is cryptococcus neoformans found in nature?
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Pigeon droppings!
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Most cases (75%) occur in __(a)__ persons. In fact almost 10% of __(b)__ patients develop cryptococcosis.
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a. immunocompromised
b. AIDS |
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T/F Cryptococcal meningitis is fatal without treatment.
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True - cerebral edema progresses to eventual brainstem compression
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How to diagnose cryptococcosis?
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Lumbar puncture and analysis of the CSF.
A more sensitive test is the cryptococcal antigen tests, which detects cryptococcal polysaccharide antigens. |
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In immunocompromised patients, candida albicans can cause:
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1. esophagitis - extension from oral thrush into esophagus
2. disseminated - can invade the blood stream and virtually every organ |
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Aspergillus flavus causes three major types of diseases in humans:
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1. allergic broncho-pulmonary aspergillosis
2. aspergilloma 3. invasive aspergillosis |
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Aspergilloma
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Persons with lung cavitations from TB or malignancies can grow an aspergillus fungal ball in the cavity, called an aspergilloma. This ball can be large (as big as a golf ball) and require surgical removal.
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Invasive aspergillosis
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Usually occurs in immunocompromised hosts such as patients who are neutropenic after chemo or patient on high dose steroids for treatment of graft vs host disease. End stage AIDS patients can sometimes develop this as well.
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Aspergillus flavus and other fungi can produce toxins, called__(a)__. The toxin produced by aspergillus flavus is called the __(b)__.
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a. mycotoxins
b. aflatoxin |
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What are actinomycetes?
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Bacteria acting like fungi. They frequently grow in the form of mycelia and ware water and soil saprophytes.
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What are the two types of bacteria that act like Fungi?
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Actinomyces Israelii and Nocardia asteroides
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