mycology

brooder pneumonia appearance

1. yellowish-green or whitish

2. caseous nodules on lungs (air sacs) of chicks

hyphae

the basic element of filamentous fungi with a branched and tubular structure

mycelium

web or mat-like structure of hyphae

septate

divided by cross walls or by septa

dimorphic

having two forms or phases

what temperature is the yeast form?

body temp (37 degrees celsius)

what temperature is mycelial form?

room temp (25 degrees celsius)

conidia

refers to asexual spores

is sexual phase usually seen in microbiology for fungi?

no

macrocondidia

large multi-celled conidia produced by certain dermatophytes in culture

microconidia

small conidia produced by some dermatophytes

anthroconidia

spores produced from hyphal fragmentation

phialconidia

conidia produced by phialides as in the case of Aspergillus

what are the categories of fungal diseases?

1. dermatomycoses

2. yeasts

3. subcutaneous mycoses

4. systemic mycoses

5. mycotoxices

what are the general characteristics of fungi?

1. eukaryotic

2. non-motile

3. heterotrophic organisms

what is generally larger: bacteria or fungi?

fungi

why can fungi not perform photosynthesis?

lack chlorophyll

what are the cell walls made of in fungi organisms?

chitin

how do fungi reproduce?

sexually and asexually

what are fungi resistant to?

antibacterial drugs

what is the cell characteristic of fungi?

can be unicellular or multicellular

what is the main difference between bacteria and fungi?

the composition of their cell wall

what are the morphological classifications of fungi?

1. yeast

2. mold

3. dimorphic fungi

what is the morphology of yeast?

unicellular; bud to produce daughter cell

how does yeast appear on solid media?

usually white or beige and appear like bacterial colonies

what are the typical species of yeast?

1. candida

2. malassezia

pseudohypae

chain of yeast formed when buds remain attached in a row

what diseases are associated with candida spp?

1. thrush

2. mycotic stomatitis

3. enteritis

4. crop mycosis

5. metritis

what diseases are associated with malassezia (M. pachydermatis)?

1. otitis externa

2. chronic dermatitis (alopecia, erythema, and pruritis)

what are predisposing factors to diseases associated with malassezia?

1. flea allergy

2. genetic factors

if you were to look at malassezia under a microscope, what KEY characteristic would be seen?

peanut or footprint shape of the yeast

what is a helpful identification when looking at molds (filamentous fungi)?

most mold colonies produce a pigment

what do molds tend to produce?

hyphae and conidia (spores)

how do molds tend to appear when grown on solid medium?

fluffy or cottony

what diseases are associated with aspergillus fumigatus?

1. brooder pneumonia (chicks)

2. mycotic abortion (cattle)

3. guttural pouch mycosis (horses)

4. nasal aspergillosis (dogs)

nasal aspergillosis

destruction of turbinates bones leading to profuse blood-tinged exudate from nose

what is important about the dimorphic fungi spores from mycelia?

spores from mycelia may cause infection via respiratory tract from inhalation

what are the ways of transmitting mycotic infections?

1. direct contact

2. inhalation

3. ingestion (mycotoxins)

what is the typical pathogenesis of fungi?

low morbidity and contagiousness (except for ringworm)

what is associated with chronic infections of fungal infections?

formation of granulosas

how do fungi adhere to the host cell?

cell wall glycoproteins

what allows fungi to resist phagocytosis?

production of capsules

how do fungi damage the host?

secret enzymes that all infection to spread

what are predisposing factors of fungal infections?

1. exposure to fungal spores

2. adherence to moist skin

3. prolonged antibacterial therapy

4. surgical procedures

5. lowered heat resistance

at what temperature do you transport fungal specimen?

room temperature

where should samples be taken when suspecting a fungal infection?

from the periphery site of infection; there will be no active infection in the middle

what are diagnostic tests for fungal infections?

1. wood lamp test

2. wet mound with 10% KOH

3. culture

4. PCR

what is important to note when testing for fungal infections?

the only conformational test involves culture; the rest are specultative tests

what is the minimum time for a real culture confirmational test of fungi?

4 weeks

when will positive cultures begin to appear in fungal cultures?

7-10 days

when will positive cultures of candida and aspergillus begin to appear on a culture?

24-72 hours

dermatophytosis

infection of superficial keratinized tissues (skin, hair, and nails)

what species does the microsporum of dermatophytes infect?

dogs and cats

what species does the T. mentagrophytes of the dermatophytes infect?

dogs, cats, and horses

what is the source of candida spp?

commensal of the skin, GI track, and vagina

what is the source of malassezia spp?

commensal of the skin

what is the source of microsporum spp?

restricted to skin, hair, and nails

what do we typically associate lesions with?

alopecia and nail infections

how should hair samples be collected when diagnosing dermatophytes?

hair should be plucked

why does hair need to be plucked when diagnosing dermatophytes?

spores of fungal infection are embedded within the follicle; if you cut the hair, you will not get the source of infection

for a systemic mycoses-dimorphic fungi what phase is the fungi in if it is on an animal body?

yeast phase

for a systemic mycoses-dimorphic fungi what phase is the fungi in if it is in the environment?

mycelial phase (mold)

what is the common source of infection for cryptococcus neoformans?

bird droppings

what are the symptoms of cryptococcus neoformans?

1. sneezing

2. hemorrhagic nasal discharge

what is important that can be used as a diagnostic in cryptococcus neoformans?

the fungi forms capsules

what species does cryptococcus neoformans infect?

sporadic disease in cats (more often) and dogs

what are the forms of feline cryptococcosis?

1. cutaneous cryptococcosis

2. systemic

3. central nervous system

how is cryptococcus neoformans diagnosed?

1. wet mounds

2. culture

3. agglutination tests

what species does blastomycosis affect?

dogs and humans

what is the environment for blastomycosis?

soil-borne

how is blastomycosis transmitted?

aerosol inhalation leads to granulomatous lesions in the lungs

what is the source of histoplasmosis?

soil enriched with bat or bird excreta

what species are effected by histoplasmosis?

more often dogs, less common in cats

how is histoplasmosis spread?

infection via inhalation which causes granulomatous lesions in the lungs

what disease is associated with coccidiodomycosis?

valley fever

what is the infectious agent of valley fever?

soil or dust-borne dimorphic fungus

what species is affected by valley fever

dogs are most affected but important to know humans can be infected as well

how is valley fever spread?

infection by inhaling infective anthrospores

what disease is associated with sporotrichosis?

rose garderners disease

mycotoxicosis

consequence of ingestion of grains or forage containing mycotoxins produced by certain fungi

mycotoxins

toxic substances or metabolites produced by fungi

how can mycotoxicosis be presented?

1. non-contagious, sporadic

2. acute or chronic poisoning

what are the diseases associated with mycotoxins?

1. aflatoxicosis

2. ergotism

3. facial eczema

4. ochratoxicosis

what are the ways of transmission for mycotoxosis?

1. ingestion

2. direct contact

how is mycotoxicosis diagnosed?

1. signs of decreased feed consumption or feed refusal

2. test for toxins in feed

how can we control mycotoxins

good agricultural practices and sufficient drying of crops

what is the distinctive shape of malassezia?

shoe or peanut shape

what is the distinctive shape of cryptococcus?

capsule shaped