Pathogenic Fungi Chapter 22 Flashcards
Describe the dimorphic nature of pathogenic fungi.
-They have 2 different types of growth/shapes dependent on environment. -Grow as mycelial thallii in the environment at 30C (grow hypha) -Grow as spherical yeasts in the body -invasive form (budding yeast cells)
Describe the disease of Coccidiodomycosis?
-Most often result in pulmonary conditions -Many show no or few symptoms -infections in healthy individuals resolve on their own -some may develop more serious infections -dissemination to other sites occurs most in immune suppressed individuals
How are most systemic mycoses acquired?
Through inhalation -Begins as generalized pulmonary infection, then becomes systemic. Then disseminated via the blood to the rest of the body.
List 4 pathogenic fungi
-Blastomyces -Coccidioides -Histoplasma -Paracoccidoides
Medical Mycology
The diagnosis, management and prevention of fungal diseases. Difficult to diagnose/treat due to being missed, misinterpreted, and that fungi are often resistant to anti-fungal agents.
Systemic mycoses
Infections that spread throughout the body.
What 4 diseases can be caused by clinical histoplasmosis?
-Chronic pulmonary histoplasmosis -Chronic cutaneous histoplasmosis -Systemic histoplasmosis -Ocular histoplasmosis
What is the difference between: pulmonary, cutaneous, osteoarticular, and meningeal blastomycosis?
P.B. -Most common -initial pulmonary lesions are most asymptomatic -symptoms are nonspecific -disease resolves in most, yet may become chronic in some. C.B. -Painless lesion on the face and upper body O.B. -Spread of fungus to the spine, pelvis, cranium, ribs, long bones or subcutaneous tissue surrounding joints M.B. -Spread of fungus to the central nervous system -Can occur in AIDS patients because of immune-suppression.
What is the epidemiology and pathogenesis of histoplasmosis?
-Histoplasma capsulatum is the causative agent (most common fungal pathogen affecting humans) -Found in E.US, Africa, and S. America -Found in moist soils high in nitrogen -Most infections occur through inhalation of spores -Cutaneous inoculations are extremely rare -H. capsulatum is phagocytized by macro-phages in the lungs (disperse fungi beyond lungs via blood and lymph)
What is the epidemiology and pathogenicity of Coccidomycosis?
-Coccidiodes immitis is the causative agent -Almost exclusive in SW US, and northern Mexico -Fungi in very dry areas; desert soil, rodent burrows, archeological remains, mines -Infection rates risen in endemic areas due to population expansion and increased recreational activities -Inhaled arthoconidia germinate into spherules in the lung that release large number of spores as they mature.
What is the epidemiology of mycoses?
-Fungi spores everywhere -Acquired via inhalation, trauma, or ingestion -Infrequently spread -Most not contagious -Dermatophytes/ringworm major exception -Epidemics due to mass exposure of environmental source fungi -Generally not reportable -Information on occurrences lacking
What risk factors increase opportunistic mycoses?
-Invasive medical procedures -Medical therapies -Certain disease conditions -Specific lifestyle factors
What are the general characteristics of systemic mycoses caused by opportunistic fungi?
-Don’t typically affect healthy humans -Infections are limited to people with poor immunity -More important as the number of AIDS patients rises -Difficult to identify because their symptoms are often atypical
What is the epidemiology and pathogenicity of Pneumocystis juroveci?
-formerly referred to P. carinii -obligate parasite -Majority of individuals are exposed to this by the age of 5 -Transmission most likely occurs through inhalation -Infection in immune-competent is usually asymptomatic -Common opportunistic fungal infections of AIDS patients —presence of the disease is almost diagnostic for AIDS —Can result in death if left untreated
What disease does Pneumocystis jiroveci cause?
Pneumocystis Pneumonia
What is the epidemiology and pathogenicity of Candida albicans?
-Includes various opportunistic infections and diseases -Candida albicans most common causative agent -common microbiota of the skin and mucous membranes -One of the few fungi transmitted between individuals -All cases of disease result from an opportunistic infection -can produce a wide range of diseases -Systemic disease seen mostly in immune compromised individuals
What diseases are associated with C. albicans?
-Vaginal candidiasis–Vaginal yeast infection -Diaper rash -Oral candidiases in infants -onchyomycosis–nail fungus
What are the general characteristics of Aspergillus?
-Several diseases caused by fungi in the genus Aspergillus -Can be found throughout the environment -Disease occurs from the inhalation of the fungal spores -Most commonly causes only allergies
What three pulmonary diseases are caused by Aspergillus?
~Hypersensitivity aspergillosis —manifests as asthma or other allergic symptoms ~Noninvasive aspergillomas —masses of fungal hyphae form in the cavities following pulmonary tuberculosis ~Acute invasive pulmonary aspergillosis —may present as pneumonia ~Cutaneous and systemic aspergillosis also occur
What is the main causative agent of Cryptococcosis?
Cryptococcus neoformans
What are the two varieties of Cryptococcosis and who do they affect?
-Cryptococcus neoformans gattii–Immune competent individuals -Cryptococcus neoformans neoformans–AIDS patients
What are the general characteristics of Cryptococcus neoformans?
-Results from inhalation of spores or dried yeast in bird droppings -Characteristics enhance the pathogenicity of the fungus -Ability to resist phagocytosis -Predilection for the central nervous system -Occurs in individuals with little immune system function
What are the diseases associated with Cryptococcus neoformans?
-Primary pulmonary cryptococcus –Asymptomatic or mild pneumonia -Cryptococcal meningitis –MOst common clinical form of cryptococcal infection –Follows dissemination of the fungus to the CNS -Cryptococcoma –Rare condition in which solid fungal masses can form -Cutaneous cryptococcosis –skin lesions or inflammation of subcutaneous tissues
What are the general characteristics of the superficial, cutaneous and subcutaneous mycoses?
-Are the most commonly reported fungal diseases -All are opportunistic infections -localized at sites at or near the surface of the body Acquired by person-person contact or environmental exposure -Diseases are usually not life threatening
What is the common name of dermatophytoses?
Ringworm
What are the characteristics of dermatophytoses?
-Infections of the skin, nails, or hair caused by dermatophytes -fungi use keratin as nutrient source and colonize dead tissues -May trigger cell-mediated immune response that damages living tissues -can be spread from person-to-person -Genera of ascomycetes cause most dermatophytoses -dermatophytoses show a variety of clinical manifestations
What are the characteristics of Malassezia furfur infections?
-Normal microbiota of the skin -causes pityriasis (depigmented or hyperpigmented patches of scaly skin) -Diagnosis based on presence of budding yeast and short hyphal forms in clinical samples -superficial infections are treated with topical antifungal agents -extensive infections treated with oral therapy -relapses of Malassezia infections are common
What are the general characteristics of the cutaneous and subcutaneous mycoses?
-Fungi are commonly found in the soil -Less common than superficial mycoses –requires traumatic introduction of fungi beneath the outer layers of skin -most lesions remain localized to subepidermal tissues in the skin
What group of people tend to get infected with chromoblastomycosis and phaeohyphomycosis?
Individual who work in the soil
What type of disease does chromoblastomycosis cause?
skin lesions on skin surface that progressively worsen
What type of disease does phaeohyphomycosis cause?
-involves colonization of the nasal passages and sinuses -Occurs in allergy sufferers and AIDS patients
What are the characteristics of mycetomas?
-Tumor-like infections -caused by mecelial fungi in the division Ascomycota -Infections are most prevalent near the equator -Fungi are found in the soil -Fungi introduced via wounds from contaminated twigs, thorns, or leaves -Individuals who work in soil are at most risk -Nodules form at site of infection and slowly worsen and spread -Bone destruction can cause permanent deformity
What is the epidemiology and distribution of Sporothrix schenckii?
-Subcutaneous infection usually limited to the arms & legs -fungi found in soil -those who work with plant material at highest risk -most infections occur in Latin America, Mexico, and Africa
How does the disease sporotrichosis present?
-Initially produces nodular lesions around the infection site -fungi may enter the lymphatic system from primary lesion –secondary lesion occur on the skin along the course of lymphatic vessels
What are the general characteristics of fungal intoxication and fungal allergies?
-Some fungi produce mycotoxins or cause allergies -fungal mycotoxins can cause toxicosis -fungal allergens can elicit hypersensitivity response in sensitive individuals. -Two types of toxicosis –Mycotoxicosis (caused by eating mycotoxins) –Mycetismus (Mushroom poisoning from eating fungus)
Where are mycotoxins found?
In grains or vegetables
What are aflatoxins?
-best known mycotoxins -Fatal to many vertebrates -Carcinogenic at low levels when consumed continually -Can cause liver damage and liver cancer -Prevalent in the tropics -Some are used to make drugs (include ergot alkaloids produced by Claviceps purpurea)
What are the side effects of ingesting aflatoxins?
Can cause liver damage and liver cancer
What is mushroom poisoning called?
Mycetismus
What are the side effects of “poisonous” mushrooms?
-can cause neurological dysfunction, hallucinations, organ damage, or death -damage cell structure and inhibit mRNA synthesis -cause liver damage
What is the deadliest mushroom?
The “Death Cap” mushroom
What are some other side effects of mushroom poisoning?
-Gyromitra esculenta causes diarrhea, convulsions, and death -Cortinarius gentilis causes thirst, nausea, and kidney failure
What type of reactions are seen with fungal allergens?
-Asthma, eczema, and hay fever type III hypersensitivity reactions occur much less frequently
