VMCB122 Mycology

Hypersensitivity

An allergic reaction to molds and spores

Mycotoxicoses

Poisoning by feeds and food products contaminated by fungi that produce toxins from the grain substrate

Mycetismus

Ingestion of toxin (mushroom poisoning)

Infection

Caused by pathogenic fungi

Mycoses

Infections caused by fungi

Mold

Branching filamentous (Hyphae); Observed either in the environment or medium)

Yeast

Unicellular/Oval; Produced within the body of the host (in vitro 37C) Reproduce by budding

Yeast-like form

Chains of elongated ellipsoidal cells with constriction between them; Produced by Candida

Thallus

Whole body of a mold

Mycelium

Organized mesh, composed of filaments with or without branching hyphae; for absorption of food

Rhizoid

Root-like structures

Hyphae

Basic building block of fungi; long and branched, threadlike filaments; Tubular cell wall; Grow and secrete enzymes; Expand into new food resources

Septate

Hyphae divided into cells by cross walls

Coenocytic

No cross walls

Vegetative

Penetrate the artificial medium to absorb the nutrients

Aerial

Grow above the surface of the medium

Fertile

Aerial hyphae carrying reproductive structures (spores)

Coenocytic

Non-septate hyphae which allow uninterrupted flow of protoplasm

Trichophyton mentagrophytes

Spirally coiled hyphae

Microsporum audouinii

Short, unilateral projections from hyphae resembling teeth of a comb

Trichophyton schoenleinii

Irregular projections of the hyphae that collectively resemble a chandelier or the antler of a deer

Microsporum canis

Closely twisted hyphae resembling a nodule

Epidermophyton floccosum

Chain of elongated hyphal cells expanded at one end to produce a tennis-racquet-like arrangement

Spitzenkorper

Growth tip and vesicles

Ergosterol

Major sterol in plasma membrane

Microtubules

Targeted by griseofulvin

Chemical compounds

Source of energy

Organic compounds

Electron and carbon source

Mold

Grow aerobically in artificial culture medium at 20- 30C.

Yeast

37C

3.8-5.6

pH requirement

4-5%

Sugar concentration

Glucosamines

Required for chitin and various vitamins

Phylum Deuteromyces

Not capable of sexual reproduction

Conidia

Sporangiospores

Asexual spores

Fission

It produces two similar daughter cells

Budding

New organism grows from the body of the parent and detaches

Fragmentation of hyphae

Separation of individual hyphae from mycelium

Coenocytic

Spore formation: asexual spores vary from one species to another

Arthroconidia

Formed when hyphae fragment through splitting of CW or septum

Sporangiospores

Develop within a sac (sporangium) at a hyphal tip

Conidiospores

Spores that are not enclosed in a sac but produced at the tips or sides of the hypha

Blastospores

Produced from a vegetative mother cell budding

Gametangium

Sex organelle of fungi

Antheridium

Male (sexual process)

Oogonium

Female (sexual process)

Plasmogamy

Fusion of gametangia

Ascospores

These meiospores are single celled and are produced within a sac-like structure known as ascus

Basidiospores

Same as ascospores but are produced within a club-shaped structure known as basidium

Zygospores

Produced by the fusion of two compatible thali or their gametangia

Oospores

Special sexual spores that are produced within female gametangia

Pythium insidiosum

Causative agent of pythiosis

Dermatophytosis

Comprise majority of skin mycoses; "skin plants"; ringworm fungi

Dermatomycoses

Caused by yeast and normally saprophytic; filamentous fungi; generic term

Dermatophytes

Fungal molds that require keratin for growth; Produce extracellular enzymes (keratinases)

Arthrospores

Infectiour form of dermatophytes

Microsporum

Characterized by large, rough thick-walled multiseptated macroconidia

Microsporum canis

Has septate hyphae, with numerous macroconidia; macroconidia are rather long (10-25 X 35-110 μm), spindle or fusoid in shape

Microsporum gypseum

Has septate hyphae along which sessile or stalked clavate (club shaped) microconidia; The fusiform (spindle shaped) macroconidia are relatively thin walled, verrucose (with bumpy surface) and contain about 3 - 6 internal cells

Trichophyton

Cylindrical, clavate to cigar-shaped thin- walled or thick-walled smooth macroconidia that are produced rarely and in small numbers; Microconidia are one celled and round or pyriform. They are numerous and are solitary or arranged in clusters.

Trichophyton mentagrophytes

Produces septate hyphae (show typical spiral hyphae) from which branched conidiophores extend; microconidia: spherical to pyriform; macroconidia: cigar shaped

M. canis

Most important etiologic agent in cats

M. canis; M. mentagrophytes

Most important etiologic agent in dogs

T. verrucosum

Most important etiologic agent in cattle

T. equinum; M. equinum

Most important etiologic agent in cats

Colts

Horses most susceptible to fungal infection

T. mentagrophytes var quinckeanum

Most important etiologic agent in rats

M. nanum

Most important etiologic agent in pigs

T. gallinae

Most important etiologic agent in chicken

Malassezia pachydermatis

Reproduction: unilateral budding

Malassezia pachydermatis

Pathogenesis: target cornified epithelial cells

Malassezia pachydermatis

The typical bottle-shaped yeast cells with a wide septum between mother and daughter cells

Cytology

Most useful tool for diagnosis for otitis/dermatitis

Malassezia pachydermatis

Footprint or peanut-shaped yeasts (>10 yeast per high power field)

Malassezia pachydermatis

Lipid (sterile olive oil) required for Malassezia except for

Trichosporon

Causative agent of piedra and severe mastitis in cows

Piedra

Formation of small white to light brown nodules that appear on the hairs of the mane (horses) and tail (monkeys)

Sporothrix schenckii

Organism resides in soil, implanted into skin by puncture wound or cut

Sporothrix schenckii

Most common SC mycotic disease in US

Sporothrix schenckii

Occupational hazard for florists, gardeners and forestry workers

Sporothrix schenckii

Yeast form is budding cells sometimes called cigar-shaped bodies

Coccidioides immitis

Reputation as the most virulent fungal pathogen; potential toll for bioterrorists

Coccidioidomycosis

San Joaquin Valley fever, Valley fever, desert disease or rheumatism, Posadas disease

Coccidioidomycosis

Common cause of community-acquired pneumonia

Coccidioidomycosis

Majority of people infected are asymptomatic or indistinguishable from ordinary upper respiratory infection; Resolves in a few weeks and results with a lasting immunity

Coccidioides

Mold: Barrel-shaped, thick-walled cells, 2- 4 μm by 3-6 μm; separated by empty cells (disjunctors), through which breaks occur when arthroconidia are dispersed

Coccidioides

Yeast: Arthroconidia grow into spherical sporangia With birefringent walls, "spherules" (10-100 μm in diameter), which by internal cleavage produce several hundred "endospores" (2-5 μmin diameter)

Dogs

Most frequently affected by coccidioidomycosis

Blastomyces dermatitidis

Dimorphic: grow as a budding yeast in humans but as a mold on culture media and in the environment

Ajellomyces dermatitidis

Teleomorphs of blastomycosis

Blastomyces dermatitidis

Found predominantly in moist soil enriched with decomposing organic debris

Blastomyces dermatitidis

More often progressive than histoplasmosis and coccidioidomycosis

Blastomyces dermatitidis

Three clinical forms: cutaneous, pulmonary and disseminated

Blastomyces dermatitidis

Mold: Conidiophores with spherical or oval smooth- walled conidia, 2-10 μmin diameter.

Blastomyces dermatitidis

Yeast: Thick-walled yeast, 5-20 μm in diameter, that reproduces by single buds attached by a broad base; characterized by the thick, double-contoured cell wall

Blastomycosis

Not spread person-to-person; Percutaneous infection probably occurs in dogs with organisms entering tissue via traumatic inoculation but generally solitary lesions should be considered part of a systemic disease

Blastomycosis

Microconidia or hyphal fragments are inhaled and then convert to yeast form within the alveolar spaces of respiratory tract; uptake by phagocytic cells

Cryptococcus neoformans

The only encapsulated systemic mycotic agent (virulence)

Cryptococcus neoformans

Common inhabitant of soil and are found in large numbers in association with bird excreta