mycology midterm 1

Why fungi is good

some are microbiota/commensal, antiobiotics/penicillin

Fungi species that cause human disease/infection

300 species

teleomorph, perfect

sexual, meiotic

anamorph, imperfect

asexual, mitotic

Fungi phylogeny

eukaryotes, closer to animals phylogenetically

order of classification

kingdom → phylum → genus → species

fungi composition

rigid cell walls containing chitin, many have ergosterol in their cell membrane

three phylum of fungi

ascomycota, basidiomycota, mucormycota(zygomycetes)

deuteromycetes

fungi imperfecti, only reproduce asexually

fungal properties

contain organelles, heterotrophic, osmiotrophs

heterotrophic

requires organic compounds for energy and carbons sources, uses exoenzymes to digest then ingest

osmiotrophs

obtain nutrients by absorption

fungal life style/nutritional modes

saprobes(live on dead materials), parasites, mutualists

mold morphology

multicellular, grow in microscopic filaments(hyphae)

hyphae characteristics

apical growth, tangle together to form larger mass(mycelium)

spitzenkorper

special organelle for hyphal apical growth

septate vs aseptate

septate has sections, aseptate has none

hyaline vs dematiaceous hyphae

hyaline is clear, dematiaceous is pigmented

thermally dimorphic

fungal form changes based on temperature

yeast reproduction

usually asexual, budding(asym), fission(symm)

mold reproduction

sexual spores(meiosis), asexual spores(mitotic)(disease causing)

Conidia

Ascomycetes and basidiomycetes: asexual spores produced on ends of specialized hyphae(conidiophores) and released from tip or side of hyphae

sporangiospores

mucormycetes: asexual spores produced in a specialized sac/capsule(sporangia)

vegetative hyphae

hyphae that fgathers nutrients, located below soil or under agar

aerial hyphae

hyphae that can become reproduction form, located above soil or above agar

fungal cell wall

defined by chitin, can be immunogenic, immunopathogenic, immunomodulatory

immunogenic

elicits immune response

immunopathogenic

response contributes to development of disease

immunomodulatory

changes way immune system responds

fungi commensals

GI: Candida
outer skin: Malassezia

Respiratory tract: pneumocystis jirovecii

Fungi general concepts

slow growers and movers, many can invade into tissue/vessels, many commensals, cryptococcus is an opportunistic and primary pathogen

mycotoxicosis

a toxin in grains, corn, nuts, associated with liver cancer, aflatoxin(aspergillus flavus)

ergotism symptoms

vomit, diarrhea, hallucinations, gangrene

causes for increases in fungal infections

HIV/AIDS pandemic, advances in medical tech, climate change and urbanization, increased diagnostics, testing, and reporting

Histology and direct exam

GMS(silver stain) or periodic acid-schiff(PAS)

GMS(silver stain)

targets carbohydrates, appears black/brown on light green

periodic acid-schiff(PAS)

targes polysaccharides, glycoproteins, red/pink/purple

histology pros and cons

see pathologic effect but not sensitive, cant do susceptibilities, difficult to ID species

culture pros and cons

specific and can do susceptibility, not very sensitive and takes time

antigen testing pros and cons

fairly fast but varied specificity and sensitivity, no susceptibility testing

PCR pros and cons

specifc but no susceptibility and difficult to distinguish colonization from pathogen

serology pros and cons

specifc but not good in immunocompromised patients, difficult to distinguish colonization or past exposure vs clinical disease

cutaneous and subcutaneous mcyoses

high incidence and generally non fatal, antifungals target ergosterol(azoles, terbinafine)

Pityriasis versicolor presentation

fairly common, nosocomial, causes altered pigmentation, seborrheic dermatitis, dandruff

Pityriasis versicolor treatment

topical or oral azoles

Malassezia spp

basidiomycete, normal skin flora that infects oily areas of skin, lipophilic, dimorphic, cause of Pityriasis versicolor

tinea negra presentation

rare, causes painless brown/black macules on hands and feet, occurs after contact with aqueous environment or in tropical/subtropical areas

tinea nigra treatment

dandruff shampoo, topical antifungals

Hortaea werneckii

ascomycete, causes tinea nigra

white piedra presentation

uncommon, causes white nodules on hair that can surround and invade the hair shaft, can leads to trichosporonosis, common in temperate, humid, or tropic climates

white piedra treatment

cut hair, topical/oral azoles

Tirchosporon spp

basidiomycete, no teleomorph state, yeast is hyphal form with septa

dermatophytes

group of molds that infect keratinous tissue, rare cause of dissemination disease except for immunocompromised
Trychophyton rubrum, Microsporum canis, Epidermophyton floccosum

trichosporonosis

disseminated white piedra that can occur in severely immunocompromised

Tinea capitis

hair shaft and scalp

Tinea barbae

skin and facial hair

tinea corporis

ringworm

tinea cruris

groin, “jock itch”

tinea pedis

athlete’s foot

tinea unguium

nails, “onychomycosis”

diagnosis for tineas

skin scraping for KOH, microscopy, culture

Trichophyton rubrum

ascomycete, most common dermatophyte, anthropophilic, has diffusible red pigment, can produce penicillin

Trichophyton rubrum conidia

microconidia: teardrop shaped
macroconidia: cigar shaped with thin walls

Microsporum canis

ascomycete, zoophilic(corporis and capitis)

Microsporum canis conidia

microconidia: rare
macroconidia: spindle shaped with thick walls

Epidermophyton floccosum

ascomycete, anthropophilic

epidermophyton floccosum conidia

microconidia: none
macroconidia: club shaped, “beaver tail” or “raquet” hyphae

Tineas treatment

tricophyton, microsporum, epidermophyton
topical antifungals: azoles and terbinafine

tinea capitus treatment

oral terbinafine, azoles, griseofulvin

Onchyomycosis/tinea unguium treatment

oral terbinafine, may be months of treatment

subcutaneous mycoses

sporothrichosis, chromoblastomycosis

sporothrichosis

“rose handlers disease,” spreads from puncture site centrally, causes nodules and swelling of lymph nodes, causes primary pulmonary/disseminated if inhaled

sporothrichosis treatment

azoles, ampho b if severely ill, previously with potassium iodide or hyperthermia

chromoblastomycosis

caused by traumatic implantation of dematiaceous yeast-like organisms into skin or subcutaneous tissue, occurs in the tropics/subtropics and rural area

chromoblastomycosis presentation

causes warty dermatitis, ulcerated or crusted, “chromo”

chromoblastomycosis diagnosis

histology: brown walled, round, non budding fungal form, “copper pennies”

chromoblastomycosis treatment

prolonged antifungal treatment, may require surgery

systemic endemics

ascomycetes that are molds in the environment, inherently virulent and causes primary pulmonary infection, often asymptomatic with initial lung infection, lab hazards, risk based on geographic exposure

coccidioides location

endemic to sw US, Mexico, central and south America, now in WA
hyperendemic to central valley of CA and phoenix/tuscon AZ

coccidioides yeast/yeast like

arthroconidia is infectious unit from soil, looks like spherule with endospores

coccidioides disease

extracellular, acute valley fever, causes skin nodules, arthiritis, flu-like, usually self limited pneumonia

coccidioides frequency

60% asymp, less than 5% disseminate, less than 5% recur

coccidioides risk of dissemination

risk for immunocompromised and pregnancy

coccidioides diagnosis

serology and antigen tests, cultures as a mold at 25C

coccidioides treatment

usually no treatment, flu/itraconazole for immunocompromised, ampho for more serious or disseminated

coccidioides meningitis

coccidioides that can occur in immunocompetent, requires lifelong antifungals

histoplasma capsulatum location

hyperendemic to Mississippi and Ohio river valleys, other varieties hyperendemic to central US, in caves/bat droppings

histoplasma yeast/yeast like

dimorphic, oval yeasts with no capsule

histoplasma disease

intracellular in macrophages, inhaled conidia form yeasts and multiply within macrophages in the lung, can disseminate, usually self resolving acute respiratory but can cause calcified nodules in the lung

histoplasma frequency

90% asymp, risk of dissemination for AIDS, immunocompromised, and kids

histoplasma diagnosis

blood or urine antigen test

histoplasma treatment

itraconzaole for mild-mod with symptoms, mild dissemination, NOT involving CNS
ampho B for moderately severe/severe, dissemination or CNS
12 rule: at least 12 weeks for penumonia, at least 12 months for dissemination

blastomyces dermatitidis location

moist soil, wooded areas, hyperendemic to mississippi and ohio st. lawrence river valleys, AR, KY, WI, hunters and outdoor work

blastomyces yeast/yeast like

dimorphic, lollipop conidia, broad based budding yeast

blastomyces disease

extracellular, inhalation of conidia results in clinical pulmonary infection and robust immune response, cutaneous disease if traumatic inoculation

blastomyces diagnosis

sputum or lung culture, can do an antigen but it could cross react, serology NOT useful

blastomyces treatment

treat everyone due to high rate of dissemination and severe disease, ampho B in serious and CNS, itraconazole for more mild symptoms

paracoccidioides location

central and south america

paracoccidioides yeast/yeast like

mariner’s wheel

paracoccidioides disease

extracellular
10% acute diease with quick progression: fever, weight loss, organomegaly, bone marrow dysfunction
90% chronic/reactivation disease: more common in males(estrogen), involves lungs and mucosa