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112 Cards in this Set
- Front
- Back
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Mycosis
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Human mycotic disease; associated with true fungal pathogens that exhibit some degree of virulence or with opportunistic pathogens that take advantage of defective resistance.
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Fungi as Infectious Agents
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- Molds and yeasts are widely distributed in air, dust, fomites, and normal flora.
- Humans relatively resistant. - Fungi are relatively nonpathogenic - Of the 100,000 fungal species, only 300 have been linked to disease in animals - Human mycoses are caused by true fungal pathogens and opportunistic pathogens. |
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A true or primary fungal pathogen is....
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A species that can invade and grow in a healthy, noncompromised animal host.
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Thermal Dimorphism
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Biphasic characteristic of the life cycle because it is initiated by changing temperature. In general, these organisms grow as molds at 30 C and as yeasts at 37 C.
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Example of Thermal dimorphism
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Candida albicans grow in your armpits will appear differently than candida in your esophagus.
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Opportunistic pathogen
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- weak to nonexistent invasiveness or virulence
- Host's defenses must be impaired to some degree for the microbe to gain a foothold. |
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Table 22.1 Primary True Pathogens
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Histoplasma capsulatum
Coccidioides immitis |
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Table 22.1 Pathogens with Intermediate Virulence
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Sporothrix schenckii
Dermatophytes (Microsporum, Trichophyton, Epidermophyton) |
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Table 22.1 Secondary Opportunistic Pathogens
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Candida albicans, Aspergillus spp., Cryptoccus neoformans, Pneumocystis jiroveci
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Table 22.3 Common Opportunistic Fungi and Conditions that Predispose patients to them
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Candida
Aspergillus Cryptococcus Zygomycota species |
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Table 22.3
Candida is associated with... |
Antibiotic therapy, catheters, diabetes, corticosteroids, immunosuppression
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Table 22.3
Aspergillus is associated with.... |
Leukemia, corticosteroids, tuberculosis, immunosuppression, IV drug abuse
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Table 22.3
Cryptococcus is associated with... |
Diabetes, tuberculosis, cancer, corticosteroids, immunosuppression
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Table 22.3
Zygomycota species is associated with... |
Diabetes, cancer, corticosteroids, IV therapy, third-degree burns
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Most striking adaptation to survival and growth in the human host is what?
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To switch from hyphal cells to yeast cells.
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Which pathogens are considered an emerging medical concern and account for 10% of all nosocomial infections?
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Opportunistic mycotic infections
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Fungal pathogens that exist in a category between true pathogens and opportunists ?
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Sporothrix and Dermatophytes
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Epidemiology of the Mycoses (3 things)
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1. Most fungal pathogens do not require a host; noncommunicable infections.
2. Dermatophytes and Candida naturally inhabit humans. 3. Predictable geographical pattern: climate, soil |
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Which fungal infections are the probably the most prevalent?
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Dermatophytoses.
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How are dermatophytoses transmitted?
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Shared personal articles, public facilities, swimming pools, gymnasiums, infected animals contact
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Pathogenesis of the fungi:
Describe Portals of entry |
1.Primary mycoses - respiratory; inhaled spores.
2. Subcutaneous - inoculated skin; trauma 3. Cutaneous and superficial - contamination of skin surface |
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Pathogenesis of the fungi:
Virulence factors |
- Thermal dimorphism
- Toxin-like substances - Adhesion factors - Hydrolytic enzymes - inflammatory stimulants |
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Pathogenesis of the fungi:
Antifungal defenses |
- Integrity of the skin, mucous membranes, respiratory cilia
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Pathogenesis of the fungi:
Most impt defenses are? |
Cell-mediated immunity, phagocytosis, and the inflammatory reaction.
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Diagnosis of Mycotic Infections
requires? |
Isolation, microscopic examination of stained specimens, culturing in selective and enriched media and specific biochemical and serological tests.
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Diagnosis of Mycotic Infections:
In examining fungi samples, large round or oval budding cells are evidence of what? |
Yeasts
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Diagnosis of Mycotic Infections:
In examining fungi samples, you see thick, branching strands suggesting what? |
Hyphae
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Control of Mycotic Infections: (3 things based on p.667)
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1. Treatment: based on antifungal drugs
2. Immunization = usu. ineffective 3. Prevention limited to masks and protective clothing to reduce contact with spores or surgical removal of tissues. |
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Organization of Fungal Diseases: Mycoses are presented according to what?
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Type, level of infection, and degree of pathogenicity.
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Organization of Fungal Disease: 2 major classes are ?
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1. True Pathogens
2. Opportunistic mycoses |
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Organization of Fungal Disease:
True pathogens encompass ? |
Systemic
Subcutaneous Cutaneous Superficial |
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Give a general description of the phrase "systemic mycoses."
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In systemic mycoses, the fungus disseminates from the lungs or other sites into the circulation.
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Systemic Infections by True Pathogens: (6 notes)
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- Restricted to endemic regions
- Infection occurs when matter containing conidia is disturbed - Spores germinate in the lungs - Infection can become systemic - Spores may be inoculated into the skin - All diseases result in immunity |
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What is Primary Pulmonary Infection (PPI)?
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An infection from spores germinating in the lungs into yeasts or yeastlike cells; usu. asymptomatic or mild; and/or parallels tuberculosis
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What is the most common true pathogen (causing a systemic infection) ?
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Histoplasma capsulatum
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Describe Histoplasma.
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1. Most common true pathogen. Causes histoplasmosis.
2. Dimorphic 3. Distributed worldwide; US eastern/central 4. Moist soil in nitrogen content 5. Inhaled conidia produce PPI that may progress to systemic involvement of diff organs and chronic lung disease. |
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Describe Coccidioides immitis.
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1. Disease: Coccidioidomycosis
2. Shape: Blocklike arthroconidia in the free-living stage and spherules containing endospores in the lungs 3. Lives in alkaline soils in semiarid, hot climates and is endemic to SW US 4. Acquired: inhaled from dust, creates spherules, and can form nodules in the lungs |
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What fungus demonstrates the greatest virulence of all mycotic pathogens?
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Coccidioides immitis
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What two fungi cause SYSTEMIC infections?
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Histoplasma
Coccidioides |
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Why is an infection termed a subcutaneous infection?
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Because it involves tissue within and just below the skin.
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Subcutaneous Mycoses (3 points)
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1. Fungi transferred directly into traumatized skin, they can invade
2. Most species are greatly inhibited by higher temperatures of the blood and viscera. 3. Diseases are progressive |
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Describe Sporothrix Schenkii.
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- Subcutaneous mycosis aka Gardener's disease
- Very common saprobic; decomposes plant matter in soil - Infects appendages and lungs - Acquired when contaminated plant matter penetrates the skin and the pathogen forms a nodule, then spreads to nearby lymph nodes |
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Cutaneous Mycoses (4 points)
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1. Infections strictly confined to keratinized epidermis (skin, hair, nails), are called dermatophytoses
2. Closely related and similar shapes 3. Causative agent of ring worm varies case by case 4. 3 pathogens: trichophyton, microsporum, epidermophyton |
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Horticulturists, gardeners, farmers and basket weavers should be mindful of which mycosis in their occupation?
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Sporothrix (Sporotrichosis)
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Common terms for dermatophytoses are?
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Ring worm and tinea
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What are the characteristics of Trichophyton?
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Thin-walled, smooth macronidia, and numerous micronidia
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What are the characteristics of Microsporum?
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Thick-walled, rough macroconidia, and sparser microconidia
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Tinea Capitis
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Ringworm of scalp
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Tinea Barbae
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Ringworm of beard
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Table 22.5
Describe the dermatophyte Trichophyton: Disease, targets, transmission. |
Disease = ringworm of scalp, body, beard, nails, Athlete's foot
Targets = Hair, skin, nails Transmission = human>human; and animal>human |
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Table 22.5
Describe the dermatophyte Microsporum: Disease, targets, transmission. |
Disease = Ringworm of scalp, skin
Targets = scalp hair, skin (not nails) Transmission = A>H, S>H, H>H |
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Table 22.5 Describe the dermatophyte Epidermophyton: Disease, targets, transmission
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Disease = ringworm of the groin and nails
Targets = Skin, nails; not hair Transmission = Strictly human to human |
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What are dermatophytes' natural reservoirs?
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Humans, animals, and soil
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What promotes infection by dermatophytes?
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Hardiness of the dermatophyte spore, presence of abraded skin, and intimate contact
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What's the infection from dermatophytes like?
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Long infection period with localized inflammation and allergic reaction to fungal proteins.
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Tinea corporis
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Ringworm of body
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Tinea cruris
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Ringworm of groin
aka jock itch |
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Tinea pedis
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Ringworm of foot
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Tinea manuum
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Ringworm of hand
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Tinea unguium
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Ringworm of nails
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Besides transmission between humans, soil, and animals, what's another way cutaneous mycoses (dermatophytes) is transmitted?
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Spread through fomites (inaminate objects that can spread disease)
E.g. borrowing a brush, using shower |
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Opportunistic Mycoses (Name 3)
General definition. |
- Needs an immunocompromised host
- 3 kinds: Candida, Aspergillus, Pneumocystis |
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Describe Candidiasis
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1. Infections by Candida
2. Candida albicans = widespread yeast 3. Can be short-lived, superficial skin irritation to really bad systemic disease 4. Forms off-white, pasty colony with a yeasty odor |
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Describe candida albicans
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- Normal flora of oral cavity, genitalia, lg intestine or skin of 20% humans
- Causes thrush - thick, white growth on mucus membranes of mouth/throat - Vulvovaginal yeast infection - causes ulceration and discharge - Cutaneous candidiasis - chronically moist areas of skin and burn patients |
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What is the dominant opportunistic pathogen, causing the majority of invasive infections?
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Candida
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What is the opportunistic pathogen that accounts for the most lung infections?
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Aspergillus
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Describe Aspergillus.
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1. Causes Aspergillosis.
2. Identified through macro, culture, PCR (DNA) test. 3. Transmitted through inhaling of conidia in granaries, barns and silos |
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Fungal Allergies and Intoxications
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1. Fungal spores are common sources of atopic allergies.
2. Fungal toxins lead to mycotoxicoses usually caused by ingesting or inhaling fungal toxins. 3. Aflatoxin - product of Aspergillus flavus from grains, corn, peanuts; lethal to poultry/livestock. Carcinogenic. |
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The ability of a fungus to alternate between hyphal and yeast phases in response to temperature is called ?
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Dimorphism
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Which phase of a fungal life cycle is best adapted to growing in a host's body?
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Yeast
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Primary pathogenic fungi differ from opportunistic fungi in being?
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More virulent
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True pathogenic fungi .....?
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Cause PPI and are endemic to specific geographic areas
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Examples of fungal infections is/are communicable include: dermatomycosis, sporotrichosis, candidiasis. (which ones?)
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Dermatomycosis, sporotrichosis
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Histoplasmosis has the greatest endemic occurrence in which region?
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Midwest US
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Coccidioidomycosis is endemic to which geographic region in the US?
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Southwestern
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Skin testing with antigen is a useful epidemiological procedure for which one: histoplasmosis, coccidiodomycosis, candidiasis.
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Histoplasmosis, coccidioidomycosis.
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A mycetoma is a ....?
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Deeply invasive fungal infection of the foot or hand
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Dermatophytic fungi attack the ..... in the ......?
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Keratin; skin, nails, hair
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Examples of dermatophyte genera are which ones: epidermophyton, sporothrix, trichophyton.
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Epidermophyton, trichophyton
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Candida albicans is the cause of ....., an infection of the ......../
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Thrush, mouth
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Cryptococcocosis is associated with ?
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Pigeon droppings
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Which fungus does not commonly cause systemic infection?
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Malassezia
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Which of the following is the cause of mycotoxicosis?
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Aspergillus
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Common name for Coccidioidomycosis
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San Joaquin valley Fever
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Common name for Histoplasmosis
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Ohio Valley Fever
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Common name for Blastomycosis
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Chicago disease
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Common name for Sporotrichosis
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Rose-Gardener's disease
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Common name for Dermatophytosis
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Tinea
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Common name for Candidiasis
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Yeast infection
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A true fungal pathogen must exhibit what characteristic?
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Thermal Dimorphism
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Where is Histoplasma capsulatum found within the United States?
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Ohio and Mississippi river valleys
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What are the most prevalent of all fungal infections?
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Candidiasis
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Dermatophytoses can be spread by all but which of the following? Gym, public facilities, personal articles, swimming pools, sexual contact.
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Sexual contact
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What component of the fungi is most involved in initiating mycoses?
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Spores
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Why are yeasts more invasive than hyphal forms of fungi?
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Because they multiply more rapidly.
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Which fungus causes mycoses of the hair, skin, and nails?
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All dermatophytes
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Which class of antifungal drugs inhibits an enzyme in egosterol synthesis and is administered topically to treat dermatophyte infections?
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Allylamines
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What type of fungal infection involves the stratum corneum and occasionally the upper dermis?
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Cutaneous
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Who experiences the majority of cases of histoplasmosis?
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Adult males
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Where is the primary location of Histoplasma capsulatum microconidia growth?
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Within the cytoplasm of macrophage
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Which fungus is the most virulent of all mycotic pathogens?
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Coccidioides immitis
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Outbreaks of coccidioidomycosis have been associated with all but which of the following?
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Hurricane Isabel
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How is coccidioidomycosis diagnosed?
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Examination of sputum, spinal fluid, or biopsies for spherules
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Most incidents of human sporotrichosis arise following what event?
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A puncture or scratch wound
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What is the causative agent of athlete's foot?
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Trichophyton
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What is the Latin name that corresponds to athlete's foot?
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Tinea pedia
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What organisms cause fungal infections that are strictly confined to nonliving tissues and its derivatives?
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Dermatophytes
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Candida albicans causes local infections in all but which of the following sites? Mouth, pharynx, vagina, lungs, endocardium
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Endocardium
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What factor is important in the pathogenesis of Cryptococcus neoformans?
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Capsule
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What is the reservoir for Cryptococcus neoformans?
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Birds
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Who typically develops Pneumocystis carinii infections?
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People with deficient immune systems
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Where do Aspergillus infections usually occur?
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Lungs
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