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135 Cards in this Set

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Describe the lesion associated with Actinomycosis.
An abscess with draining sinuses, characterized by having sulfur granules in the exudate.
What are the staining and morphological characteristics of the Actinomyces sp.?
Fine Gram-positive filaments (may be short and branching). They are not acid fast.
Name the two genera that contain agents that cause Antinomycosis.
Actinomyces sp. Propionibacterium sp.
In which anatomic location is Actinomycosis most often found?
Cervicofacial
What is the source of infection for Actinomycosis?
The organism is found among the normal flora of the mouth. It is introduced into tissues by dental procedures.
What predisposes an individual to development of Actinomycosis?
Malnutrition. Alcoholism. Systemic disease. Disruption of mucosal surfaces. Depressed immunity.
What can be seen by direct examination of pus from Actinomycosis?
Sulfur granules. Fine Gram-positive filaments.
How is Nocardiosis transmitted to humans?
Via the pulmonary route or after trauma with a contaminated object.
What are the etiologic agents of root-surface caries?
Actinomycoses viscosus. Actinomycosis naeslundii.
What predisposes a patient to development of root surface caries?
Age.
What is the normal habitat of Nocardia sp.?
The soil.
Name three different infections that can be caused by Nocardia.
Thoracic. Cutaneous. Meningitis.
What is seen when pus from a Nocardia infection is examined?
Delicate multiple branching or fragmented filaments.
What are the staining and morphological characteristics of Nocardia sp.?
Gram-positive, partially acid fast, delicate filaments.
Are fungi procaryotic or eukaryotic?
Eukaryotic
What is the chemical nature of the cell walls of fungi?
Peptidomannan, chitin and glucans.
What is a blastoconidium?
A yeast cell (the plural is blastoconidia).
What type of general structure do molds have?
The are comprised of long filaments called hyphae.
What is the name of a mass of hyphae?
Mycelium.
In relation to fungi, what does dimorphic mean?
A fungal organism that can grow in two different forms depending upon the culture conditions. Often seen by growth at 37 C vs 25 C.
What is the name for the reproductive cell of a filamentous fungus?
Spore - it is now usually called a conidium.
What is the term for hyphae that has no cross walls or septa?
Aseptate or coenocytic.
What is the term for hyphae that have cross walls?
Septate hyphae.
What types of spores are formed by fragmentation of thick-walled hyphal elements that are barrel shaped?
Arthroconidia.
What are the asexual spores that are produced when yeast cells bud?
Blastoconidia.
What is the name of a fungal element composed of several elongated blastoconidia that are arranged in a straight line and that appear to be hyphae?
Pseudohyphae.
Name the thick-walled conidium that develops within a hyphal element by modification of an existing cell.
Chlamydospore.
What is the name given to a very small spore (or conidium)?
Microconidium
What is the name given to a large spore (conidium)?
Macroconidium.
What is the specialized hyphal element upon which conidia are produced?
Conidiophore.
What is the name of a sac-like structure that contains asexual spores?
Sporangium
What is the name of the conidia (spores) that are contained within a sporangium?
Sporangiospores (or sporangioconidia).
Which class of fungi is characterized by having aseptate hyphae and sporangiospores?
Zygomycetes.
Which class of fungi is characterized by having ascospores and septate fungi?
Ascomycetes.
Which class of fungi is characterized by having basidiospores and septate hyphae?
Basidiomycetes.
Which class of fungi does not have a sexual stage?
Deuteromycetes.
What does anthropophilic mean?
A fungus that preferentially grows on man rather than animals or in the soil.
What does zoophilic mean?
A fungus that preferentially infects an animal rather than man.
What does geophilic mean?
A fungus that has a soil reservoir.
What is the difference between a mycotoxicoses and a mycoses?
A mycotoxicosis is caused by a toxin that is ingested by man. A mycosis is a infection due to a fungus.
Name four different types of mycoses.
Superficial. Cutaneous. Subcutaneous. Systemic.
Are most fungal infections from an endogenous or exogenous source?
Most are obtained from an exogenous source.
Which fungus is obtained from an endogenous source and where does it reside in the body?
Candida albicans. Found normally in the gut, mouth and vagina.
What is the target of attack for most of the antifungal agents?
They interfere with ergosterol synthesis.
What is the etiologic agent of Tinea versicolor?
Malassezia furfur.
What does the agent of Tinea versicolor look like when skin scrapings are digested with 10% KOH and examined under the microscope?
Yeast cells and hyphae that look like spaghetti and meat balls.
Which group of fungi is responsible for the ringworm infections?
The dermatophytes.
What is different about infection with dermatophytes as compared to the superficial mycoses?
They infect all layers of the skin, hair and nails and produce significant lesions.
Which three genera are involved in ringworm infections?
Trichophyton. Microsporum. Epidermophyton.
What is characteristic about to spores and hyphae of the Trichophytons?
Thin-walled, smooth, cigar-shaped macroconidia Numerous microconidia en engrappe (grape-like clusters) or en thyrse (along hyphae). Spiral hyphae seen.
What tissues are infected by the Trichophyton sp.?
Hair. Skin. Nails.
What do the spores of Microsporum sp. look like?
Thick-walled, rough, spindle-shaped macroconidia. Microconidia.
What tissues are infected by Microsporum sp.?
Skin. Hair.
What do the spores of Epidermophyton floccosum look like?
Club-shaped, smooth, thin-walled macroconidia in clusters of 2-3. No microconidia.
What tissues are infected by Epidermophyton?
Skin and nails.
What is the id reaction?
The production of dermatophytosis-like symptoms at uninfected sites on an infected person. It is an allergic response.
What type of lesion(s) occurs in Sporotrichosis?
Chronic cutaneous and lymphocutaneous nodular lesions with adjacent lymphatics that suppurate, ulcerate and drain.
How does man obtain sporotrichosis?
The fungus is inoculated by trauma into the skin. Inhalation causes pulmonary disease which is rare.
What is the etiological agent of sporotrichosis?
Spororthrix schenckii.
What is the natural habitat of Sporothrix schenckii?
Soil, bark, rose bushes, straw.
What does Sporothrix schenckii look like in tissues?
Elongated, irregular yeast cells (cigar shaped). Not always seen in direct preps.
67What does Sporothrix schenckii look like after growth at 30 C?
Septate hyphae with tapered conidiophores that bear clusters of conidia (spores) at the tips in floweret arrangements (some say they look like daisies).
What is the treatment for sporotrichosis?
Oral potassium iodide.
What is the treatment if lymphocutaneous sporotrichosis relapses or if the disease is disseminated or pulmonary?
Amphotericin B
What type of infection is usually caused by Coccidioides immitis?
Respiratory infection that resolves rapidly.
What happens when coccidioidomycosis goes systemic?
It spreads to meninges, bones, joints, subcutaneous and cutaneous tissues in about 0.5 to 1% of infected individuals.
What does Coccidioides immitis look like in tissues?
Spherules with a thick wall containing endospores.
What does Coccidioides immitis look like when grown at 30 C?
Mycelial growth that produces barrel-shaped arthroconidia with a disjunctor cell between each arthroconidium.
What is the infectious agent of Coccidioides immitis?
Arthroconidia that are aerosolized and inhaled.
What is the natural habitat and endemic area of Coccidioides immitis?
Soil of the lower Sonoran life zone in North, Central and South America. In the USA it is found in southern Texas, southern New Mexico, Southern Arizona and in southern and central California.
What types of clinical infection are caused by Histoplasma capsulatum?
Inapparent, subclinical or benign lung infection - 95% of cases. Chronic progressive lung disease which can go systemic - may mimic TB.
What does Histoplasma capsulatum look like in tissues?
Small yeast cells are seen inside of macrophages.
What does Histoplasma capsulatum look like when grown at 30 C?
Beige to light brown mold characterized by septate hyphae that bear microconidia and large tuberculated macroconidia. The tuberculated macroconidia are the key identifying feature.
What does H. capsulatum look like when grown at 37 C on Brain Heart Infusion agar?
Small single-budding yeast (blastoconidia) with a thin neck between mother and daughter cells.
What is the natural habitat and endemic area of histoplasmosis?
Soil with a high nitrogen content. Endemic area is the Mississippi and Ohio River Valleys. Oklahoma is in the endemic area.
What types of infections are caused by Blastomyces dermatitidis?
Benign self-limiting pulmonary infection. Disseminated infection from lungs to other sites of the body especially skin and bone.
What does Blastomyces dermatitidis look like in tissues?
Blastoconidia (yeast) that are thick-walled with a large isthmus between mother and daughter cell (some call this a broad-based bud).
What does Blastomyces dermatitidis look like when grown on Brain Heart Infusion agar at 37 C?
The yeast phase grows. Thick-walled yeast cells with a broad based bud (isthmus) between mother and daughter cell.
What does Blastomyces dermatitidis look like when grown at 30 C?
Mycelial growth with septate hyphae and microconidia.
What is the natural habitat and endemic area for blastomycosis?
Soil is the natural habitat. Endemic area: Mississippi and Ohio River Valley, the area extends further over to the east coast than for Histoplasmosis and does not include Oklahoma.
How is man infected with Blastomycosis and Histoplasmosis and what is the infectious particle?
Inhalation. The microconidia are the infectious particle for these two organisms.
What is the treatment of choice for the systemic mycoses?
Amphotericin B.
Infections with Candida albicans can occur at many sites of the body. What are these locations?
Vagina. Oral cavity (thrush). Esophagus. Perianal. Superficial skin. Systemic.
What is the primary predisposing factor for development of mucocutaneous candidiasis?
T cell deficiency.
What is the primary predisposing factor for development of systemic candidiasis?
Neutropenia.
Besides T cell deficiency and neutropenia, what other factors can predispose the patient for the development of candidiasis?
Antibiotic use - due to effects on the normal flora. Pregnancy. Endocrine abnormalities. Local tissue damage. Malnutrition. Severe burns. Drug abuse. IV catheters.
What does Candida albicans look like in tissues?
Budding yeast cells, hyphae and pseudohyphae.
How can Candida albicans be differentiated from other Candida species in the laboratory?
C. albicans makes germ tubes when incubated at 37 C in serum. C. albicans will make chlamydoconidia (chlamydospores) when grown on special media (corn meal or EMB agar).
What treatment is used for superficial skin infections due to Candida infections?
Nystatin
What treatment is used for mucocutaneous Candida infection?
Ketoconazole
What treatment is used for treatment of systemic candidiasis?
Amphotericin B
What is the natural habitat of Candida albicans?
Normal flora of the gut, vagina and oral cavity.
What is the primary site of infection with Cryptococcus neoformans?
The lungs.
Upon dissemination systemically, C. neoformans has a predilection for what tissue?
The central nervous system.
Which form of diseased that is caused by C. neoformans infection is most frequently diagnosed?
Meningitis.
What predisposes patients to development of infection with Cryptococcus neoformans?
T cell deficiency. Especially important in the AIDS population.
What does Cryptococcus neoformans look like in spinal fluid or other tissues?
An encapsulated yeast cell. Capsule visualized in India ink preparations.
What does Cryptococcus neoformans look like when grown in the laboratory at 30 C?
An encapsulated yeast cell.
What does Cryptococcus neoformans look like when grown in the laboratory at 37 C?
An encapsulated yeast cell.
What test is commonly done on serum or spinal fluid to detect infection with Cryptococcus neoformans?
A test for the presence of cryptococcal antigen. Latex beads coated with antibody to cryptococcal antigen will agglutinate in the presence of serum or CSF that contains the antigen.
What is the prognosis of non-compromised patients with localized pulmonary lesions due to C. neoformans?
Good.
What is the prognosis for immunocompromised patients with systemic infection with C. neoformans?
Very poor.
What is the recommended treatment for cryptococcal meningitis?
A combination of 5-FC and amphotericin B.
After treatment of AIDS patients with cryptococcosis, they may be placed on maintenance therapy for life with what drug?
Fluconazole.
What is the natural habitat and endemic area for Cryptococcus neoformans?
Found in the soil, especially in areas containing large amounts of weathered (not fresh) pigeon feces. The organism is found worldwide.
How is man infected with C. neoformans?
Believed to be by inhalation of small, dessicated forms of the yeast found in the soil.
What types of patients are at risk of developing pneumocystis pneumonia?
Immunocompromised such as: AIDS. Bone marrow transplant. Chronic corticosteroid treatment.
When do people become infected with Pneumocystis and how are they infected?
By 4 years of age. Respiratory route.
What immune response is primarily responsible for protection against pneumocystis pneumonia?
CD4-mediated (or cell-mediated)
What two names may you see as the name for the etiologic agent of pneumocystis pneumonia?
Pneumocystis jiroveci - new name. Pneumocystis carinii - old name.
What are the symptoms of pneumocystis pneumonia?
Dry cough. Fever. Progressive shortness of breath. Rapid breathing. (this disease does not occur in the immunocompetent)
What range of infections can be caused by Aspergillus species?
A wide spectrum from allergic to invasive infection.
What is the most common species of Aspergillus that causes human infection?
Aspergillus fumigatus.
Aspergillus organisms are found throughout the world.
The correct answer is: True
What type of hypersensitivity can be induced after inhalation of Aspergillus conidia?
Immediate hypersensitivity (IgE mediated).
What clinical features are characteristic of allergic bronchopulmonary aspergillosis?
Fungal growth in the bronchi. Asthma. Immediate hypersensitivity to aspergillus skin test antigen. Positive culture for Aspergillus from sputum.
What clinical features are commonly associated with aspergilloma?
Fungus ball in the lungs. Can be asymptomatic or result in productive cough and hemoptysis.
What is the common site of infection in noninvasive aspergillosis?
Pulmonary cavity. External ear canals. Nasal cavity, eye. Nail plate. Paranasal sinuses.
Which individuals are most susceptible to noninvasive aspergillosis?
Immunosuppressed.
What type of immunosuppression leads to invasive aspergillosis?
Granulocytopenia (neutropenia).
What can be a potential consequence of exposure to some of the metabolites of Aspergillus?
They are toxic and carcinogenic.
What does Aspergillus look like in tissues?
Branching, septate hyphae.
What does Aspergillus look like when grown in the laboratory?
Mycelium bearing conidiophores on which are found phialides. Conidia are found at the tips of the phialides.
Why is it difficult to prove that Aspergillus was cultured from a clinical specimen?
This organism is a common contaminant in the air and therefore a contaminant of media used to grow fungi in the laboratory.
What additional information helps establish that Aspergillus is the cause of an infection other than culture in the laboratory?
Direct observation of hyphae in the clinical specimen.
What other types of tests can be used to aid in the diagnosis of Aspergillosis?
Detection of antigens by double diffusion or other immunologic assays.
What is the treatment for aspergilloma?
May range from none to surgical resection and treatment with antifungals (Amphotericin B and flucytosine).
What is the treatment for invasive aspergillosis?
Amphotericin B or itraconazole.
What is the name for the disease caused by an opportunistic mycotic infection caused by a mold in the class Zygomycetes?
Mucormycosis (also zygomycosis).
What patient groups are susceptible to the development of mucormycosis?
Ketoacidosis resulting form diabetes mellitus, drugs or uremia. Burn patients. Leukemia and lymphoma. Steroid therapy. Immunosuppressed.
Several different fungal species can cause mucormycosis but two are quite prevelent. What are these two?
Mucor. Rhizopus.
What types of infection can be caused in mucormycosis?
Rhinocerebral infection. Thoracic infection causing destruction of lung parenchyma. Localized infection after tissue trauma. Kidney infection. Cutaneous infection.
What do the fungi that cause mucormycosis look like in tissues?
Broad, irregular, branching, nonspetate hyphae. Key identifying feature: the nonseptate hyphae.
What do the organisms that cause mucormycosis look like when grown in the laboratory?
Aseptate hyphae (also called coenocytic hyphae) with sproangiophores bearing sproangia which are filled with spores (sporangioconidia). If the species is Rhizopus, rhizoids will be seen. If it is Mucor, the rhizoids will not be present.
What is the treatment for mucormycosis?
Surgical debridement and Amphotericin B