mycology

Question 1

mycology

Answer 1

most are free-living and abundant in nature; only a few are members of the human microbiome; fungi are eukaryotic microorganisms

Question 2

fungi

Answer 2

cell walls made of chitin; chitin provides a very tough cell wall; the biosynthesis of chitin provides a target for antifungal agents; fungal plasma membranes contain egosterol, which is a cholesterol analog not found in plant or animal cells; ergosterol provides a target for antifungal agents

Question 3

filamentous fungi

Answer 3

form branching tufts called mycelium; filamentous fungi grow by extending cells called hyphae; as fungal hyphae expand, its chitinous cell wall enables it to penetrate softer material, such as plant or animal cells; they can expand a great length, but eventually they run out of nutrients; the gametes develop into spores (conidia) that are easily airborne and disseminate into the environment; fungal spores can spread disease and cause allergies; the vast majority of fungi do not need to colonize or infect humans or animals to perpetuate the species

Question 4

single-celled fungi

Answer 4

unicellular fungi are called yeasts; most yeasts reproduce by mitosis through asymmetric division process known as budding

Question 5

dimorphic fungi

Answer 5

some species of fungi are dimorphic; they can exist in a mycelial or yeast form depending on the growth environment

Question 6

pathogenic fungi

Answer 6

nearly all fungal infections originate from an exogenous source either by inhalation or traumatic implantation; the exceptions are candidiasis and tinea versicolor, which are caused by opportunistic microbiota;

Question 7

saprobes

Answer 7

organisms that live on dead or decaying organic matter

Question 8

tinea versicolor

Answer 8

(superficail mycoses) - part of the nromal microbiota of the skin; hyper- or hypo-pogemented macular lesions on the upper torso, arms, and abdomen

Question 9

tinea nigra

Answer 9

(superficial mycoses) - fungi that produces melanin giving it a brown to black color; causes well-demarcated macular lesions mostly on the palms an soles

Question 10

black piedra

Answer 10

(superficial mycoses) - infects the hair shaft; causes hard nodules to form along the infected hair shaft

Question 11

white piedra

Answer 11

(superficial mycoses) - infects the hair shafts of the scalp, mustache or beard; forms a soft, pasty, cream-colored growth along the infected hair shaft

Question 12

ringworm

Answer 12

(cutaneous mycoses) - caused by a closely related group of fungi known as dermatophytes; the fungi that cause ringworm can live on skin and in the environment; ringworm is spread: through contact with a person or animal who has ringworm; from the environemnt: the fungi can live on surfaces, particularly in damp areas like locker rooms and public showers

Question 13

subcutaneous mycoses

Answer 13

subcutaneous mycoses comprise a wide spectrum of fungal infections characterized by the development of lesions usually at sites of trauma where the organism is implanted in the tissue; the infection initially involves the deeper layers of the dermis, subcutaenous tissue or bone

Question 14

histoplasmosis

Answer 14

systemic mycoses - histoplasmosis is acquired from inhaling the spores or hyphal frangments of histoplasma capsulatum; once inhaled, H. capsulatum phagocytosed by pulmonary macrophages. the fungi then convet into the yeast form, which are able to replicate within the macrophages.

Question 15

h. capsulatum

Answer 15

grows in soil; especially in areas containing bird and bat excretions

Question 16

histoplasmosis symptoms

Answer 16

in most cases it is asymptomatic, but in about 5% of cases acute pneumonia develops and less often 1% is followed by progressive disseminated disease; this level of disease occurs in debilitated and/or immunosuppressed individuals

Question 17

blastomycosis

Answer 17

most infections are asymptomatic; the symptoms of blastomycosis are often similar to the symptoms of flu or other lung infecitons; in some people, particularly those with weakened immune systems, the fungi can spread to other parts of the body

Question 18

cryptococcosis

Answer 18

acquired from inhaling cryptococcus neoformans; encapsulated yeast; once inhaled, C. neoformans may infect the lungs; however, the organism has a high tendency for systemic spread to the brain and meninges; leading cause of fungal meningitis

Question 19

where is c. neoformans found

Answer 19

it lives in the environment throughout the world; the fungus is generally found in soil, on decaying wood and in bird (pigeon) droppings

Question 20

cytococcosis infections

Answer 20

extremely rare among people who have healthy immune systems; however, C. neoformans is a major cause of illness in people living with HIV/AIDS; a c. neoformans infection in the lungs can cause a pneumonia-like illness; cryptococcal meningitis occurs if the fungus spreads from the lungs to the brain; the symptoms of cryptococcal meningitis are similar to other forms of meningitis

Question 21

candidiasis

Answer 21

opportunistic mycoses - caused by a species of Candida, many of which are members of the human microbiome; candida species are monomorphic yeasts and can be found in the human oral cavity, vagina, gastrointestinal tract, and rectum; within the human host, candida species’ growth is limited by competition with other microbiota and the immune system; disease results when the fungus overgrows and offsets the balance

Question 22

oropharyngeal candidiasis

Answer 22

opportunistic mycoses - candidiasis that develops in the mouth or throat is called “thrush” or or oropharyngeal candidiasis; characterized by white patches or plaques on the tongue and other oral mucous membranes, redness and difficulty swallowing; oral thrush occurs most frequently among babies less than one month old, the elderly and groups of people with weakened immune systems

Question 23

genital candidiasis

Answer 23

opportunistic mycoses - genital/vulvovaginal candidasis is also sometimes called a “yeast infection,” and it occurs when there is overgrowth of normal yeast in the vagina; men with genital candidiasis may experience an itchy rash on the penis

Question 24

invasive candidiasis

Answer 24

opportunistic mycoses - if candida get into the bloodstream (candidemia), it can affect the blood, heart, brain, eyes, bones or other parts of the body; the most common symptoms are fever and chills that don’t improve after antibiotic treatment for suspected bacterial infections

Question 25

aspergillosis

Answer 25

caused by aspergillus, which are extremely common in the environment both indoors and outdoors; aspergillosis is acquired from inhaling spores from exogenous sources; most people do not get sick, however it is an opportunistic pathogen for people with weakened immune systems or lung diseases

Question 26

allergic aspergillosis

Answer 26

a benign allergy involving the lungs and/or sinuses

Question 27

aspergilloma

Answer 27

also called a “fungus” ball’ a ball of aspergillus grows in the lungs or sinuses but usually does not spread to other parts of the body

Question 28

chronic pulmonary aspergillosis

Answer 28

a long-term condition in which Aspergillus can cause cavities in the lungs; one or more fungal balls (aspergillomas) may also be present in the lungs

Question 29

systemic aspergillosis

Answer 29

in immunosuppressed hosts the organism spreads from its primary site (lungs) to other tissues causing infarcts and hemorrhage