LAB 12: THE FUNGI

FUNGI: FRIEND OR FOE?Both! There are fungal pathogens and beneficial fungi

• Eat them

• Help us make bread, cheese, alcoholic beverages

• Vast majority of antibiotics are made by fungi

FUNGI: FOE• Cause infections – superficial – to – systemic• Allergies – over 37 million people suffer from

allergies that are believed related to fungi (Penicillium and Aspergillus spp.)– Sick Building Syndrome (Stachybotrys sp.)

• Contaminate our water – breathing problems, watery eyes

FUNGI

- Fungi are eukaryotic ; exist as unicellular or multi-cellular organisms

- Microscopically they are larger than bacteria, with more complex cellular morphology and detail

- Two types of fungi: Yeast and Moulds

FUNGI: YEAST- Yeasts are non-filamentous, unicellular

fungi that are typically spherical or oval in shape.

- Colonial morphology is similar to bacteria.

- They reproduce by

budding.

FUNGI: YEAST

Candida albicans – most common yeast isolated from human samples

FUNGI: YEAST

FUNGI: MOULDS

- Moulds are multicellular filamentous fung.

DERMATOPHYTES

• Dermatophytes cause infections of the skin (athletes foot), hair, and nails

• Utilize the protein keratin in the epidermis

• Invasion elicits a host response ranging from mild to severe

RINGWORM – Tinea corporis

Trichophyton rubrum

White, granular or fluffy strainsReverse is deep red or purplish

Trichophyton rubrum

ZYGOMYCETES

AGENTS OF MUCOMYCOSIS

• INFECTIONS

• Allergic• Cutaneous

• Rhino cerebral• Pulmonary• GI• Disseminated

AGENTS OF MUCOMYCOSIS• RISK FACTORS

• Ketoacidosis• Neutropenia (macrophages kill spores; neutrophils kill germinating hyphae)• Iron overload• Iron chelation drug use• IDU• Immunosuppression• Emerging – LTT with voriconazole in HSCT/HM

AGENTS OF MUCOMYCOSIS• ACQUIRE

• Inhalation• Traumatic implantation• Ingestion

• TREATMENT• Frequently unsuccessful• Liposomal AMB with POZA• Debridement• Correct underlying condition

DIRECT EXAMINATION

RAIDLY-GROWING – ‘LID LIFTERS’

STRUCTURES CAN BE ASEXUAL OR SEXUAL

HYPHOMYCETES

Aspergillus fumigatus

Rapidly – growing, white, turning green

Aspergillus fumigatus

Short phialphores bearing uniserate phialides covering 2/3 of a flask-shaped vesicle

Pencillium species

Rapid growth, white becoming green

Pencillium species

• Branched or unbranched flask-shaped phialophores on metulae, smooth or rough ROUND conidia, “Penicillus” or “Brush” appearance

DIMORPHICFUNGI

Blastomyces dermatitidis• Blastomycosis

• Southeast / South-Central U.S. that border Mississippi / Ohio River valleys

• Midwest/Southern Canadian provinces bordering the Great Lakes (****Wisconsin)

• Soil (esp. around rotting wood)

Blastomyces dermatitidis• Sites of Infection

• Pulmonary (asymptomatic, acute, chronic) disseminated (bone, skin, prostate)• Cutaneous • Bone/Joint• GU• CNS

Blastomyces dermatitidis• Direct Examination

• 37ºC – large (8 x 30 µm) broad-based budding yeast forms )

Blastomyces dermatitidis

Growth rate: slow to moderate (up to 7 days)

30ºC – mycelial form with small, truncate

aleurioconidida

Coccidioides immitis Complex • Coccidioidomycosis

• C. immitis – CA, San Joaquin Valley

• C. posadasii – Southwest U.S. (TX, AZ), Central / South America

• Both – Desert Southwest and Mexico

• Soil, excavation

Coccidioides immitis Complex

• Sites of Infection

• Pulmonary**** - acute and chronic

• Skin

• Bone or joint

• CNS

Coccidioides immitis Complex

• Direct Examination

• 37C – large spherule (15–75 µm) containing endospores

Coccidioides immitis Complex

Rapidly – growing colony

Arthroconidia are thick-walled, barrel-shaped, and 2-4 x 3-6 µm in size.

Typically, these arthroconidia alternate with empty disjunctor cells.

• Histoplasmosis

• U.S. – Tennessee/Ohio / Mississippi River valleys, Central America, Asia Africa and Caribbean

• Soil, birds and bats

Histoplasma capsulatum

• Sites of Infection• Pulmonary**** - symptomatic to fulminate

• Disseminated

• GI or CNS

• Pericarditis

• Ocular [ Presumed ocular histoplasmosis syndrome (POHS)]

Histoplasma capsulatum

• Direct Examination

• 37C – small budding yeast

Histoplasma capsulatum

Histoplasma capsulatum

Slow – growing colony

Macroconidia are tuberculate, thick-walled, round, unicellular, hyaline, large and often have fingerlike projections on the

surface. These macroconidia are also referred to as tuberculochlamydospores or

macroaleurioconidia.