Fungi Flashcards
Fungi Characteristics
Cell walls components?
Plasma membrane components?
Unicellular or multicellular organisms
Aerobic eukaryotes
Defined nuclei
Cell walls of carbohydrate and chitin
Ergosterol in plasma membrane
Saprophytic or parasitic
Sexual/ asexual production
Asexual spores by mitosis
Fungi
All yeasts, yeast like organisms, dimorphics and moulds.
Yeasts
Define?
Where do they grow?
Unicellular ogranisms that reproduce by budding.
they grow on skin, mucous surfaces and in the body.
Moulds
Define?
Give an example
Multicellular organisms that produce hyphae, mycelium and spores.
Ex: Dermatophytes- hyphae grow in skin, hair, and nails.
Dimorphic Fungi
Organisms that can produce both hyphae and yeast-like forms. Hyphae in environment (+spores) and yeasts in the infected host.
Exhibit temperature dimorphism: The temp of the environment and the host decides if theyw ill cause disease or not.
What kind of fungi are found in Veterinary Medicine?
1. Cutaneous & Superficial Mucous Membranes
a. Dermatophytes
b. Malessezia
c. Candida
2. Subcutaneous
a. sporotrichosis
3. Systemic
a. Primary Pathogens (histoplasma)- cause disease in normal animals/ people.
b. Opportunisitc pathogens (Aspergillus)- cause disease in immunocompromised people.
4. Toxins
a. mycotoxins
5. Allergy (to fungal spores)
Laboratory Diagnosis:
How can we identify fungi?
- Direct Microscopy using skin, hair, nails
- Culture using Sabarauds agar (takes days/ weeks to grow)
- Identification by morphology of hyphae, production of spores.
Yeasts
Single cells
Reproduce vegetatively by budding.
Sexual reproduction by forming ascospores within cell.
Occasionally form pseudomycelium (pseudohyphae or true hyphae may be formed)
Types of Yeasts:
- Candida
- Malessezia
- Cryptococcus
Grow Aerobically on Sabouraud dextrose agar @ 37 C.
Candida
- gram positive oval cells
- Grows aerobically on Sabourad’s dextrose agar/ Chomogenic agar at 37 C.
- Will produce true septate hyphae in tissues which are the invasive forms. (C. albicans)
- Yeasts on mucus membranes, pseudohyphae
- Forms germ tubes which are hyphae in serum.
- Produces chlaymdospores on corn meal agar. These are thick walled resting cells.
What disease does Candida albicans cause in..
Cattle?
Pigs?
Dogs?
Birds?
Man?
- Cattle:
a. Mycotic abortion
b. Ruminal infections
c. Mastitis - Pigs:
a. Dermatitis - Dogs:
a. chronic enteritis and dermatitis
b. vaginitis/ vulvitis - Birds:
a. crop infections
b. enteritis - Man:
a. Mucosal/ systemic infection
What is the relationship between C. albicans and diabetes?
Most infections associated with diabetes because yeast can utilize sugars in tissues for growth.
Malassezia:
What shape cells are they?
What is a species of them?
What kind of agar do they grow on?
What diseases do they cause?
What enzymes do they produce?
- Bottle Shaped Cells
- M. pachydermatis.
- Grows on Sabouraud’s agar at 37 C. but can also be supplemented with Olive oil since they are very Lipophilic.
- Lipophilic
- Produce lipase- breaks down lipids to cause infection, urease
- Cause Otitis Externa & Dermatitis.
Cryptococcus:
Most common species?
When do they cause infection and what kind of infections do they cause/ are associated with?
What kind of colonies do they form and on what agar?
What is a virulence factor of theirs?
- C. neoformans.
- Produce opportunistic infections from animals with defective cell mediated immunity causing meningitis in humans and animals
- Associated with upper respiratory tract infections.
- Nasal cavity in cats with chronic rhinitis.
- Nasal, cutaneous, neural and ocular disease in cats.
- Form Mucoid colonies Sabouraud dextros agar at 37 C.
- Have thick mucilagenous capsules that can be identified with India Ink. The capsule acts as a **virulence factor. Capsule is what gives mucoid appearance on agar. **
*
Dermatophytes:
What are the two main genera in nature/ veterinary related?
What are different modes of transmission?
What is their target structure(s)?
Infective forms?
Grow on what agar and how quickly?
Identification/ Confiramation?
- Microsporum/ Trichophyton
- Septate Branching hyphae
- Anthropophilic (human- human)
Geophilic (environment- human)
zoophilic (animal-human) - Affinitiy for keratinized structures. Digest keratin-infect skin, hair, nails.
- Arthrospores are clinical/ infectous form and are shed from infected animals.
- Microconidia and Macroconidia are 2 spores produced in lab culture.
- Grow on Sabouraud’s agar at 37 C within 7-14 days.
- Identify by surface appearance and color of underside.
- Confirm by shape of macroconidia.
What are meant by the terms ectothrix and endothrix and what fungi are involved?
This is when dermatophytes either:
a. Ectothrix- grow on the outside of the hair
or
b. Endothrix- grow on the inside shaft of the hair.
Microsporum:
What infection does this cause?
How is it transmitted?
Causes ringworm in man and animals.
Anthropophilic, zoophilic, geophilic
Can flouresce under woods lamp (UV light)
M. Canis:
What do they cause in what species?
Where do they grow?
What spores are common/ uncommon?
Flouresce?
Colony characteristics on agar?
- **Ringworm in cats and dogs transmissible to man. **
- Grows on hair with arthrospores (ectothrix)
- Microconidia are common.
- Macroconidia elliptical with up to 14 divisions (rare on isolation)
- Flouresces under woods lamp
- **Colonies on agar have smooth, white surfaces and yellow underside. **
When sampling a suspected ringworm sample what part of the definitive nucles would you want to take?
Sample the leading edge.
What are other Microsporum species and what species do they infect?
M. gypseum- dogs, many macroconidia, geophilic transmission.
M.nanum- pigs
Trichophyton
How are they transmitted?
What do they cause in what species?
Definitive characteristic of the spores?
Definitive characteristics of their hyphae?
Flouresce?
Zoophilic
Ringworm in man and animals
Club shaped macroconidia
Spiral hyphae
**No flourescence. **
Trichophyton verrucosum:
Causes what in what species?
What are spores found?
Rginworm in cattle transmissible to man.
Abundant chlamydospores
Large spore ectothrix on hair.
Colonies are slow growing.
Deep in agar.
Only Dermatophytes grow at 37 C. The rest grow at 28 C.
T. metangrophytes:
Which species affected?
Dog/ Horse
T. equinum:
Which species affected?
Horse
T. gallinae:
Which species affected?
Fowl
