Lab 12 Fungi Flashcards
Fungi habitat
Widely distributed
Environment:
Soil, water, air, decaying material
Animal, human: skin, mucous membranes, gut
Fungi morphology
Uni- or multicellular
3-100 mm
Branching
Fungi cell wall
Chitin, hemicellulose, mucopolysaccharide, protein, lipid
Imparts rigidity and osmotic stability
Fungi septa
Cross walls
Often present in hyphae (central pore)
Components of fungi cell structure
Cell wall Septa Cytoplasmic membrane (ergosterol) Nuclear membrane Nucleus Nucleolus Ribosomes ER Mitochondria Lomasome
Difference between moulds and yeasts
M: grow as branching filaments called hyphae: mycelium
Y: oval cells: colonies in a agar plate
Dimorphic
Can occur in both mould form and yeast form, depending on temperature
Fungi resistance
Sexual spores > asexual spores > vegetative parts
Good resistance
Dehydration: years
High osmotic pressure
Low pH
Fungi staining
Unstained
Simple staining: methylene blue
Yeasts are gram pos
PAS: tissue sections
Skin/hair scraping: 10% KOH
Transparent adhesive tape technique
Fungi reproduction sexual spores
Zygospora: two hyphae cells
Ascospora: ascus
Basidiospora: on club shaped structures: basidium
General characteristics of fungi
Eukaryotes Non-photosynthetic Produces exoenzymes Obtains nutrients by absorption Degrades organic materials, recycling
Phylogenetic classification of fungi is based on…?
16s and 26s ribosomal RNA gene
Asexual spore formation
Two main types of spores: conidia and sporangiospores
Conidia are forms on conidiophores.
Sporangiospores are formed within sporangium
Fungi culture
Heterotrophic: organic C, organic/inorganic N
Sabouraud agar (pH 5.5)
Dimorphic fungi in yeast phase: blood agar
Most prefer pH 5-7 except Dermatophytes that need pH 7
Grow aerobically at 25C
Resistant to antimicrobial drugs that are effective against bacteria
Selective culture: Penicillin Chloramphenicol Streptomycin Cycloheximide
Incubation temp and time of Yeast, Aspergillus sp., and Zygomycetes
37C
1-4 days
Incubation temp and time of Dermatophytes
25C
2-4 weeks
Incubation temp and time of Dimorphic fungi in mould phase
25C
1-4 weeks
Incubation temp and time of Dimorphic fungi in yeast phase
37C
1-4 weeks
Fungi biochemical examinations
Yeasts, dermatophytes
Mycotoxin production
Production of antibiotics
Fungi antigens
Complex
Serological tests in systemic diseases (yeasts)
Identification of fungi is based on:
Morphology: micro- and macroscopically
Biochemical features: yeasts
Serological examinations
On basis of genotype: PCR
5 Phyla of fungi
Microspora Ascomycota Basidiomycota Blastocladiomycota Glomeromycota: major ecological importance, symbionts with plant roots
Fungi pathogenicity
Majority are saprophytes, some cause opportunistic infections
Dermatophytes are pathogens that cause ringworm
Saprophytes: environmental fungi, commensal fungi, fungi of the skin and gut (sometimes facultative pathogens)
Mycosis
Tissue invasion
Dermatomycosis
Candida sp., Malassezia pachydermatitis
Dermatophytosis
Invasion and destruction of keratinized structures
Microsporum sp., Trichophyton sp. (moulds)
Subcutaneous mucosis
Following penetration by foreign body
Systemic mycosis
Prolonged AB therapy, immunosuppression
Mycotoxicosis
Ingestion of fungal toxins which have been produced in stored food or standing crops
Induction of hypersensitivity
Allergy: rare
Associated with chronic pulmonary disease in Bo/Eq
Dermatophytes: tricophyton, microsporum
Member of what?
Habitat, affinity
Moulds
Members of ascomycota
Affinity to keratinized structures
Colonize and invade skin, hair and nails
Dermatophytes morphology and resistance
Mycelium is often pigmented
R: arthrospores shed from infected animals, remain infective for many months
Dermatophytes culture
Slow growing: Sabouraud + yeast extract is needed Obligate aerobic Tolerate cyclohexamide in media Macroconidia formed in culture
Dermatophytes zoophilic group
Obligate pathogens
Cause characteristic circular skin lesions: RINGWORM
M. canis, M. gallinae
T. equinum, T. mentagrophytes, T. verrucosum
Trichophyton
Habitat, detection, culture
Skin, hair, feather: ringworm
Detection in skin scrapings
Culture: Sabouraud + yeast extract + cycloheximide
pH 7, 1-4 weeks in 25C
T. verrucosum
Bo, Hu: chlamydospores in chains
T. equinum
Eq, Hu
T. mentagrophytes
Ca, Fe, Hu, Rab
Microsporum 4 sp
M. gypseum (Eq, Ca, Hu)
M. canis (Ca, Fe, Eq, Hu)
M. nanum (Su)
M. gallinae (Chicken, Turkey)
Penicillum morphology
Conidiophores are brush-like
Penicillum
Penicillin producing sp:
P. notatum, P. chrysogenum
Penicillum mycotoxin producing sp
P. rubrum, P. viridicatum
Rubratoxin
Prod by penicillum sp, mycotoxin in food
Bo hepatotoxicity
Ochratoxin
Su, Av: renal toxicity
Patulin
Bo, Ov, Su: inhibition of ruminal flora, acidosis, vomiting in Su
Aspergillus sp.
Morphology, culture and member
Conidia terminally on the hyphae
Rapidly growing pigmented colonies: black pigment
Member of the phylum Ascomycota
Aspergillus sp. pathogenicity
Respiratory pathogens, acquired by inhalation of spores
A. fumigatus
Av lung mycosis, mycosis of eggs and abortion
A. flavus
Aflatoxin:
Su, Av, Bo: hepatotoxicity, immunosuppression, mutagen, carcinogen, teratogen
A. ochraceus
Ochratoxin: Su, Av
Kidney degeneration
Fusarum sp habitat, reproduction, culture
In feed
Asexual reproduction, macroconidia, microconidia
Pigment production
Mycotoxin production
F. graminearum, F. sporotrichoides
T2 and F2 toxins
T2 toxin
Bo, Su, Av: cytotoxicity, immunosuppression, hemorrhage, Su feed refusal, Bo rumenitis
F2 toxin
Bo, Su: estrogenic activity, hyperaemia, vulva edema, anestrus, reduced litter size in mature sows, reduced fertility in Bo
F. moniliforme
Fumonisin production
Fumonisin:
Leukoencephalomalacia in Eq
Pulmonary edema in Su
Stachybotrys
S. atra: utilization of cellulose, black colonies
Toxin: stachybotryotoxins
Eq, Ov, Bo, Su: cytotoxicity, hemorrhages, immunosuppression, necrotic lesions in alimentary tract
Imperfect yeasts consist of
No sexual reproduction
Candida sp
Cryptococcus
Malassezia
Candida sp., reproduction
No sexual reproduction
Reproduce by forming blastospores, pseudohyphae and septate hyphae
Candida species
C. albicans: Hu, piglet, calf, poultry: mm
C. guillermondi: Bo genital mm
C. tropicalis
C. krusei
Cryptococcus species
C. neoformans: large mucopolysacch capsule produced: mucoid colonies, infection derived from environment
Bo, Cap mastitis
Localized granuloma formation, systemic mycosis of Ca, Fe, Eq, Bo
Malassezia
M. pachydermatis: bottle shaped cells, commensals on skin
Ca, Fe dermatitis, external otitis!! Very imp
Dimorphic fungi members
Histoplasma
Sporothrix
Coccidiodes
Blastomyces
Dimorphic fungi habitat
Yeast form: in the host
Mould form: on media or environmemt
Histoplasma
Tropics, Mediterranean area
H. farciminosum
H. capsulatum
H. farciminosum
Soil, Eq epizootic lymphangitis
Similar to glanders: differentiation!
H. capsulatum
Hu, Ca, Fe: systemic respiratory mycosis
Sporothrix
S. schenckii
Saprophyte on vegetation
Eq, Ca, Fe, Hu subcut granulomatosis: sporocrichosis
Coccidiodes
C. immitis: soil
Systemic mycosis, lung (Eq, Ca, Fe, Hu)
Blastomyces
B. dermatitis: soil
Hu, Ca blastomycosis: granulomatosis
Chytridiomycosis of amphibians
