Flashcards
aug 14
Cards in this deck (46)
- 1Some medically important fungi arethermally dimorphic.
They form different structures at different temperatures. They exist as molds in the environment at ambient temperature and as yeasts in human tissues at body temperature. - 2Candida different-pseudohyphae in tissue
- 3Antifungal Agents and Cell Wall Targets“azole” agents (fluconazole, ketoconazol, itraconazole, miconazole)
Amphotericin B and nystatin
Caspofungin - 4“azole” agentsInhibit the synthesis of ergosterol
- 5Amphotericin B and nystatinBind to ergosterol in the fungal membrane thus affecting permeability and stability
- 6CaspofunginEchinocandins inhibit β-D- glucan synthase, an enzyme that functions in the synthesis of glucans that support the cell wall
- 7Microscopic examinationExamination of tissue
10% KOH prep for skin scrapings. Used for dermatophytes. KOH dissolves human cells but not fungal cells. - 8CulturingMany fungi can be cultured. There are multiple growth media for fungi. A common one is Sabouraud’s agar which has a low pH and antibiotics to inhibit bacterial growth.
After grown, they can be identified with a microscope.
inhibits bacteria growth and grows fungi - 9Serologic/immunologic testsBased on identifying fungal antigens in patient serum (or other fluids) or antibodies to fungal antigens in patient serum
- 10Cutaneous MycosesDermatophytes: Hair Skin, nails
- 11Subcutaneous Mycosesinfection through the skin, subcutaneous spread, and/or lymphatic spread
- 12Systemic MycosesDeep infections of the internal organs
- 13Opportunistic MycosesCause infection only in those with compromised defenses
- 14Fungal Infections of the Skin: Host Defense Properties of the SkinNormal skin is an impenetrable anatomical barrier to most microorganisms.
This physical barrier is 10-15 mM thick.
It is relatively dry which deters the growth of microorganisms in the skin.
Continuous sloughing of the skin assists in the elimination of microorganisms. - 15dermatophyte Colonization can occur bydirect inoculation of the skin by a contaminating organism.
Conversely, colonization can first establish a systemic infection that can then seed into the skin. - 16KOH PreparationThe skin is swabbed with 70% ETOH and allowed to air dry.
The surface is scraped to remove skin scales or hair that contain the fungus.
The specimen is treated with 10% potassium hydroxide to destroy tissue elements, specifically keratin (thus KOH is a clearing agent).
One looks for branching hyphae or yeast cells. - 17Cutaneous Infections by fungi:Diseases of the skin, hair, and nail. They are generally restricted to the keratinized layers of the skin. Caused by dermatophytes. These organisms express keratinases that can break down keratin.
The clinical manifestations of the disease are referred to as ringworm, or tinea - 18Tinea pedisathletes foot caused by Trichophyton rubrum, T. mentagrophytes, and Epidermophyton floccosum, common in adolescents and young males.
restricted to epidermis and love keratin - 19Tinea Cruris-jock itch caused by T. rubrum and E. floccosum.
- 20Tinea unguium-infection of the nail plate caused by T. rubrum and T. mentagrophytes
- 21Tinea corporis-ring worm) infection of the body skin found especially in children, it can be caused by any dermatophyte.
- 22Tinea manuuminfection of the palms of the hand, usually caused by T. rubrum.
- 23Subcutaneous MycosesThese include a wide spectrum of fungal infections characterized by the development of lesions, usually at sites of trauma where the organism implanted in the tissue. The infection initially involves the deeper layers of the dermis, subcutaneous tissue, or bone.
Most infections have a chronic insidious growth pattern that eventually extends into the epidermis and are expressed clinically as lesions on the skin surface - 24Sporotrichosis (Sporothrix schenckii)This is a dimorphic fungus. It is usually found in soil and decaying vegetation. It is usually introduced by accidental implantation.
After inoculation, a small ulcer or subcutaneous nodule appears. The organism spreads through the lymphatics. - 25Systemic MycosesMost result from inhalation of spores from soil.
-Most lung infections are asymptomatic.
-In some people there is disseminated disease, this is more likely in individuals in poor health.
-Infected people do not transmit infections to others. - 26CoccidioidomycosisMost infections subclinical; when clinical, the disease in California is known as Valley Fever, and is usually a pneumonia (40% of individuals develop symptomatic pulmonary infection).
Occasionally causes meningitis (chronic); when this happens prognosis is not good.
It is a dimorphic fungus, filimentous in the environment. The tissue phase is a sphereule that produces endospores. - 27Coccidioidomycosis Caused byCoccidioides immitis, a saprophytic soil fungus (has dimorphic physiology), which when inhaled may cause serious disease in man
- 28Diagnosis byhistory, positive skin test, serum antibody to C. immitis
- 29foundThe organism is found in the soil and earthquakes can disperse the microbe into the air.
- 30HistoplasmosisAcquired by respiratory route.
It is a dimorphic fungus, in soil it is mycelial and in the body it is a yeast that is phagocytosed by macrophages.
Causes the fungal correlate of tuberculosis. - 31Found inthe Ohio and Mississippi river valleys.
Found in soil that has bird and bat droppings to provide optimum growth conditions for the fungus. - 32Histoplasmosis: caused byHistoplasma capsulatum
- 33part 2In 5% of cases clinical symptoms of acute pneumonia occur.
Known as cave disease or spelunker’s disease. Bats can be infected.
The fungus likes areas of high nitrogen such as areas with bird or bat droppings.
Can persist in the body for years and reactivate. HIV- may cause disseminated progressive histoplasmosis - 34Opportunistic MycosesThese fungi fail to induce disease in most
immunocompetant people.
These fungi can, however, cause disease in
those individuals with impaired host defenses. - 35Cryptococcosis caused byCaused by Cryptococcus neoformans. Monomorphic yeast, expresses a polysaccharide capsule that inhibits phagocytosis.
In contrast to other fungi, it is not dimorphic. - 36Acquired throughinhalation of avian droppings, especially from pigeons.
May survive up to two years in dust. - 37PathogenesisOpportunistic- usually found in man only if cell mediated immunity is somewhat compromised
Inhaled particles are engulfed by pulmonary macrophages
Usually inactivated but if a large dose or poor host defenses, may get proliferation and spread. The capsule is antiphagocytic. - 38If in meningesget seeding of CSF and subarachnoid spread with lesions in brain (brain abscess) and meninges; also encephalitis.
Causes disease by compression of surrounding structures - 39Candidiosis or Candidiasis caused byCandida albicans which is a dimorphic fungus (pseudohyphae intissue) with both yeast and mycelial forms. These fungi are part of the normal flora of mucous membranes.
They have a limited ability to invade tissues. Skin infections can occur however, and predisposing factors include : obesity, wetness, antibacterial therapy and cellular immune deficiencies. In infants cutaneous candidiasis can result from diaper rash. - 40Immune suppression can lead to a systemic infection withCandida.
This systemic infection can then lead to the seeding of the yeast into the skin and the development of skin lesions. - 41Low pH in vagina inhibits growth ofCandida, and inhibits hyphae and pseudohyphae which predominate in pathogenic invasive candida.
- 42Dermatophytes usekeratin and infect the dermis.
- 43Coccidioides immitis-dimorphic, replicates in sphereules as endospores.
- 44Histoplasma capsulatum-dimorphic, fungal correlate of tuberculosis, present in bird and bat droppings, and in the Ohio and Mississippi river valley.
- 45Cryptococcus neoformans-monomorphic yeast, capsule, pigeons.
- 46Candida albicansopportunistic and dimorphic (pseudohyphae).
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- Flashcards on aug 14, created by Shylla T on 14/08/2020.
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- Shylla T · Aug 2020
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- Aug 14, 2020
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