Pathogenic Fungi Chapter 22

Question 1

Describe the dimorphic nature of pathogenic fungi.

Answer 1

-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)

Question 2

Describe the disease of Coccidiodomycosis?

Answer 2

-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

Question 3

How are most systemic mycoses acquired?

Answer 3

Through inhalation -Begins as generalized pulmonary infection, then becomes systemic. Then disseminated via the blood to the rest of the body.

Question 4

List 4 pathogenic fungi

Answer 4

-Blastomyces -Coccidioides -Histoplasma -Paracoccidoides

Question 5

Medical Mycology

Answer 5

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.

Question 6

Systemic mycoses

Answer 6

Infections that spread throughout the body.

Question 7

What 4 diseases can be caused by clinical histoplasmosis?

Answer 7

-Chronic pulmonary histoplasmosis -Chronic cutaneous histoplasmosis -Systemic histoplasmosis -Ocular histoplasmosis

Question 8

What is the difference between: pulmonary, cutaneous, osteoarticular, and meningeal blastomycosis?

Answer 8

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.

Question 9

What is the epidemiology and pathogenesis of histoplasmosis?

Answer 9

-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)

Question 10

What is the epidemiology and pathogenicity of Coccidomycosis?

Answer 10

-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.

Question 11

What is the epidemiology of mycoses?

Answer 11

-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

Question 12

What risk factors increase opportunistic mycoses?

Answer 12

-Invasive medical procedures -Medical therapies -Certain disease conditions -Specific lifestyle factors

Question 13

What are the general characteristics of systemic mycoses caused by opportunistic fungi?

Answer 13

-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

Question 14

What is the epidemiology and pathogenicity of Pneumocystis juroveci?

Answer 14

-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

Question 15

What disease does Pneumocystis jiroveci cause?

Answer 15

Pneumocystis Pneumonia

Question 16

What is the epidemiology and pathogenicity of Candida albicans?

Answer 16

-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

Question 17

What diseases are associated with C. albicans?

Answer 17

-Vaginal candidiasis–Vaginal yeast infection -Diaper rash -Oral candidiases in infants -onchyomycosis–nail fungus

Question 18

What are the general characteristics of Aspergillus?

Answer 18

-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

Question 19

What three pulmonary diseases are caused by Aspergillus?

Answer 19

~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

Question 20

What is the main causative agent of Cryptococcosis?

Answer 20

Cryptococcus neoformans

Question 21

What are the two varieties of Cryptococcosis and who do they affect?

Answer 21

-Cryptococcus neoformans gattii–Immune competent individuals -Cryptococcus neoformans neoformans–AIDS patients

Question 22

What are the general characteristics of Cryptococcus neoformans?

Answer 22

-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

Question 23

What are the diseases associated with Cryptococcus neoformans?

Answer 23

-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

Question 24

What are the general characteristics of the superficial, cutaneous and subcutaneous mycoses?

Answer 24

-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

Question 25

What is the common name of dermatophytoses?

Answer 25

Ringworm

Question 26

What are the characteristics of dermatophytoses?

Answer 26

-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

Question 27

What are the characteristics of Malassezia furfur infections?

Answer 27

-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

Question 28

What are the general characteristics of the cutaneous and subcutaneous mycoses?

Answer 28

-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

Question 29

What group of people tend to get infected with chromoblastomycosis and phaeohyphomycosis?

Answer 29

Individual who work in the soil

Question 30

What type of disease does chromoblastomycosis cause?

Answer 30

skin lesions on skin surface that progressively worsen

Question 31

What type of disease does phaeohyphomycosis cause?

Answer 31

-involves colonization of the nasal passages and sinuses -Occurs in allergy sufferers and AIDS patients

Question 32

What are the characteristics of mycetomas?

Answer 32

-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

Question 33

What is the epidemiology and distribution of Sporothrix schenckii?

Answer 33

-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

Question 34

How does the disease sporotrichosis present?

Answer 34

-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

Question 35

What are the general characteristics of fungal intoxication and fungal allergies?

Answer 35

-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)

Question 36

Where are mycotoxins found?

Answer 36

In grains or vegetables

Question 37

What are aflatoxins?

Answer 37

-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)

Question 38

What are the side effects of ingesting aflatoxins?

Answer 38

Can cause liver damage and liver cancer

Question 39

What is mushroom poisoning called?

Answer 39

Mycetismus

Question 40

What are the side effects of “poisonous” mushrooms?

Answer 40

-can cause neurological dysfunction, hallucinations, organ damage, or death -damage cell structure and inhibit mRNA synthesis -cause liver damage

Question 41

What is the deadliest mushroom?

Answer 41

The “Death Cap” mushroom

Question 42

What are some other side effects of mushroom poisoning?

Answer 42

-Gyromitra esculenta causes diarrhea, convulsions, and death -Cortinarius gentilis causes thirst, nausea, and kidney failure

Question 43

What type of reactions are seen with fungal allergens?

Answer 43

-Asthma, eczema, and hay fever type III hypersensitivity reactions occur much less frequently